There was an error in this gadget

Sunday, 19 October 2008

Foreign Body Removal, Rectum

Anorectal foreign bodies are usually inserted transanally for sexual or medicinal purposes. Rectal foreign bodies may also be observed with body packing or stuffing or after prior oral ingestion of the object. Anorectal foreign bodies are more common in men than in women.

Rectal foreign bodies may include such objects as bottles, vibrators, fruit, vegetables, and balls. Cylindrical objects are common. In addition, thermometers may accidentally break while a rectal temperature is being obtained.

Be aware that patients have usually made multiple attempts to remove the object prior to presentation in the emergency department. Patients may create unusual stories to explain how the object became lodged in the rectum.

Read more HERE

Sunday, 5 October 2008

Astrocytoma

Background

Astrocytomas are CNS neoplasms in which the predominant cell type is derived from an immortalized astrocyte. Two classes of astrocytic tumors are recognized—those with narrow zones of infiltration (eg, pilocytic astrocytoma, subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma) and those with diffuse zones of infiltration (eg, low-grade astrocytoma, anaplastic astrocytoma, glioblastoma). Members of the latter group share various features, including the ability to arise at any site in the CNS, with a preference for the cerebral hemispheres; clinical presentation usually in adults; heterogeneous histopathological properties and biological behavior; diffuse infiltration of contiguous and distant CNS structures, regardless of histological stage; and an intrinsic tendency to progress to more advanced grades.

Numerous grading schemes based on histopathologic characteristics have been devised, including the Bailey and Cushing grading system, Kernohan grades I-IV, World Health Organization (WHO) grades I-IV, and St. Anne/Mayo grades 1-4. Regions of a tumor demonstrating the greatest degree of anaplasia are used to determine the histologic grade of the tumor. This practice is based on the assumption that the areas of greatest anaplasia determine disease progression.

This chapter focuses on the widely accepted WHO grading scheme that relies on assessments of nuclear atypia, mitotic activity, cellularity, vascular proliferation, and necrosis. WHO grade I corresponds to pilocytic astrocytoma, WHO grade II corresponds to low-grade (diffuse) astrocytoma, WHO grade III corresponds to anaplastic astrocytoma, and WHO grade IV corresponds to glioblastoma multiforme (GBM). This article is confined to low-grade and anaplastic astrocytomas. GBM and pilocytic astrocytoma are not discussed in this chapter (for more information, see Glioblastoma Multiforme).
Pathophysiology

Regional effects of astrocytomas include compression, invasion, and destruction of brain parenchyma. Arterial and venous hypoxia, competition for nutrients, release of metabolic end products (eg, free radicals, altered electrolytes, neurotransmitters), and release and recruitment of cellular mediators (eg, cytokines) disrupt normal parenchymal function. Elevated intracranial pressure (ICP) attributable to direct mass effect, increased blood volume, or increased cerebrospinal fluid (CSF) volume may mediate secondary clinical sequelae. Neurological signs and symptoms attributable to astrocytomas result from perturbation of CNS function. Focal neurological deficits (eg, weakness, paralysis, sensory deficits, cranial nerve palsies) and seizures of various characteristics may permit localization of lesions.

Infiltrating low-grade astrocytomas grow slowly compared to their malignant counterparts. Doubling time for low-grade astrocytomas is estimated at 4 times that of anaplastic astrocytomas. Several years often intervene between the initial symptoms and the establishment of a diagnosis of low-grade astrocytoma. One recent series estimated the interval to be approximately 3.5 years. The clinical course is marked by a gradual deterioration in one half of cases, a stepwise decline in one third of cases, and a sudden deterioration in 15% of cases. Seizures, often generalized, are the initial presenting symptom in about one half of patients with low-grade astrocytoma.

For patients with anaplastic astrocytomas, the growth rate and interval between onset of symptoms and diagnosis is intermediate between low-grade astrocytomas and glioblastomas. Although highly variable, a mean interval of approximately 1.5-2 years between onset of symptoms and diagnosis frequently is reported. Compared to low-grade lesions, seizures are less common among patients with anaplastic astrocytomas. Initial presenting symptoms most commonly are headache, depressed mental status, and focal neurological deficits.
Mortality/Morbidity

Morbidity and mortality, as defined by the length of a patient's history and the odds of recurrence-free survival, are correlated most highly with the intrinsic properties of the astrocytoma in question. Typical ranges of survival are approximately 10 years from the time of diagnosis for pilocytic astrocytomas (WHO grade I), more than 5 years for patients with low-grade diffuse astrocytomas (WHO grade II), 2-5 years for those with anaplastic astrocytomas (WHO grade III), and less than 1 year for patients with glioblastoma (WHO grade IV).
Race

Although genetic determinants are recognized in astrocytoma development and progression, astrocytomas do not differ intrinsically in incidence or behavior among racial groups. Demographic and sociological factors, such as population, age, ethnic attitude toward disease, and access to care, have been reported to influence measured distributions.
Sex

No clear sex predominance has been identified in the development of pilocytic astrocytomas. A slight male predominance, with a male-to-female ratio of 1.18:1 for development of low-grade astrocytomas, has been reported. A more significant male predominance, with a male-to-female ratio of 1.87:1 for the development of anaplastic astrocytomas, has been identified.
Age

Most cases of pilocytic astrocytoma present in the first 2 decades of life. In contrast, the peak incidence of low-grade astrocytomas, representing 25% of all cases in adults, occurs in people aged 30-40 years. Ten percent of low-grade astrocytomas occur in people younger than 20 years; 60% of low-grade astrocytomas occur in people aged 20-45 years; and 30% of low-grade astrocytomas occur in people older than 45 years. The mean age of patients undergoing a biopsy of anaplastic astrocytoma is 41 years.

Read more HERE

Monday, 8 September 2008

Wednesday, 3 September 2008

Monday, 1 September 2008

Saturday, 9 August 2008

Friday, 1 August 2008

Sexual and Gender Identity Disorders

History

The study of sexual deviancy began just before the turn of the 20th century as the taboo of discussing sexuality was beginning to lift. Early pioneers included Richard von Kraff-Ebing, Albert Moll, August Forel, Iwan Bloch, Magnus Hirschfield, Havelock Ellis, and Sigmund Freud. Their work was not well accepted, and they were regarded with disdain.

Several psychiatric concepts were prominent at this time. One of them was a constitutional predisposition of unknown origin called degeneration, which refers to an innate neurologic weakness that is transmitted with increased severity to future generations and produces deviations from the norm. Masturbation was blamed for a list of diseases including insanity, suicide, self-mutilation, and tuberculosis. The law of association of ideas suggests that when sex and another experience occur, one stimulus sets off the other.

Ellis worked against the prudish view of sex that existed at the time, and he advocated the decriminalization of homosexuality. Freud wrote on fetishism, masochism, and the theory of perversions. These early investigators of sexual deviation provide an important principal: "Not only must the act be studied, but also the person. The personal roots of deviance spring from an interaction of the individual's biological nature and his early life experiences."

Disorders of human behavior remain difficult to understand, identify, and treat. Few data are available, too much of our knowledge is based on speculation and unsupported theory, and societal stereotypes influence our perceptions. Good science-based research remains difficult, and monetary, ethical, and legal concerns complicate such research.

PARAP
Sexual deviation is a term applicable to a subclass of sexual disorders termed paraphilias. Paraphilias are associated with arousal in response to sexual objects or stimuli not associated with normal behavior patterns and that may interfere with the establishment of sexual relationships. In modern classification systems, the term paraphilia is preferable to sexual deviation because it clarifies the essential nature of this group of behaviors (ie, arousal in response to an inappropriate stimulus).

The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR), the prevailing resource for diagnostic criteria of paraphilias, describes the essential feature of paraphilias as recurrent, intense, sexual urges and sexually arousing fantasies generally involving nonhuman objects, the suffering or humiliation of oneself or partner, or children or other nonconsenting persons. The DSM-IV-TR describes 8 of the more commonly observed paraphilias and makes reference to several other examples. People who experience one paraphilia may also experience other paraphilias, although the paraphilia may occur as an isolated event. Commonly, people who manifest paraphilias also exhibit personality disorders, substance abuse problems, or affective disorders.

Prevalence

Paraphilias are rarely diagnosed in clinical settings. Large commercial markets in paraphiliac pornography and paraphernalia are testaments that prevalence is high. Pedophilia, voyeurism, and exhibitionism are the most commonly observed behaviors in clinics that specialize in paraphilia treatment. Sexual masochism and sexual sadism are much less commonly observed. Approximately half of patients observed in clinics for treatment of paraphilias are married.

Differentials

Nonparaphiliacs may describe nonpathological use of sexual fantasies, behaviors, or objects as stimuli for sexual excitement.

In patients with mental retardation, paraphilia should be distinguished from dementia, personality change due to general medical condition, substance intoxication, manic episode, or schizophrenia in which judgment, social skills, or impulse control are compromised.

When appropriate, public urination should be distinguished from exhibitionism.

Exhibitionism

The DSM-IV-TR diagnostic criteria for exhibitionism are as follows:


The patient reports recurrent, intense, sexual urges and sexually arousing fantasies related to exposing the genitals to a stranger. Symptoms must be present for at least 6 months.
The patient experiences significant distress or impairment in social, occupational, or other important areas of functioning because of the fantasies, urges, or behaviors.
Generally, no attempt at further sexual activity with the stranger occurs, although a desire to shock the stranger sometimes exists or the exhibitionist may have a fantasy that the observer will become sexually aroused. Onset usually occurs in persons younger than 18 years but may occur later. The disorder causes significant stress or impairment in social, occupational, or other important areas of functioning. In 1975, Rooth classified 2 types of exhibitionism: Type I is the inhibited flaccid exposer, and type II is the sociopathic exposer who may have a history of other conduct. About half of adult women have witnessed indecent exposure sometime in their lives.

Exhibitionists, whether timid or brash, feel dominated by women and resent it. By exposing themselves, exhibitionists turn the table on women, dominating rather than being dominated. Exhibitionists view this act as making women their helpless victims, rather than being helpless before them. Some researchers have suggested that exhibitionists have a fragile sense of masculinity. Threats to masculinity are countered by demonstrations of manliness.

Exhibitionists have difficulty relating to women as whole people. Rather, women are present merely to provide both gratification and proof against castration. Many exhibitionists are very prudish with their wives. They go to great efforts to never look at their wives or be seen by them in the nude. Intercourse tends to be rigid and conventional.

Common to all exhibitionists is some abnormality in handling aggression and hostility. On the one hand, they must keep their anger under tight control, yet on the other hand they may become tyrannical with their family because they feel safe from retaliation.

Male genital exhibitionism is an indicator of future sexual offenses in some individuals. In a 1980 longitudinal study, Bluglass found that 7% of exhibitionists were later convicted of contact sexual offenses, including rape.

Genital exhibitionism is rare among women. This has been explained by the differences between the sexes in the development of the castration complex and the absence of a reassuring effect from showing a penis because of anatomic differences in women. Eber in a 1977 report and Kohut in a 1978 report view female exhibitionism as a disorder of bodily narcissism.

Presentation to physicians is common and may result from a sense of guilt and an inability to control the behavior. Sometimes the behavior is revealed as the result of a criminal offense. More serious underlying pathology is suggested when preferred scenes include defecation or small children.

Fetishism

The DSM-IV-TR lists the following diagnostic criteria for fetishism:


The patient experiences recurrent and intense sexual urges and sexually arousing fantasies involving the use of nonliving objects by themselves. Symptoms must be present for at least 6 months.
The patient experiences significant distress or impairment in social, occupational, or other important areas of functioning because of the fantasies, urges, or behaviors.
The fetishes are not limited to articles of female clothing used in cross-dressing (transvestic fetishism) or devices designed for genital stimulation (eg, vibrators).
Common fetishistic objects include female underwear; rubber, plastic, or leather garments; specific articles of clothing such as shoes or boots; and bodily items such as hair, odors, or feces. The disorder is more common among males than females. Prevalence is unknown. It can often be traced from adolescence and usually persists.

In the context of psychoanalytic theory, in a 1996 publication Greenacre associates fetishism with a severe castration complex in males and a more complicated and less readily recognized set of relational reactions in females. For men, the fetish serves a defensive function, a reinforcing adjunct for a penis of uncertain potency. The fetish serves to increase the efficiency of the penis, which does not perform well without it. In women, fetishism is less common, largely because of anatomic differences that allow women to conceal inadequate sexual response more readily than men. Women can develop symptoms more comparable to male fetishism when the illusion of having a phallus has gained sufficient strength to approach delusional proportions. This occurs in rare cases in which severe disturbances in the sense of reality exist.

Treatment of the specific condition (fetish), rather than the primary underlying disorder (eg, organic pathology, personality disorder) generally is unsuccessful. A variety of treatment approaches have been tried, such as aversive conditioning, cognitive therapy, and psychotherapy.

Frotteurism

The DSM-IV-TR lists the following diagnostic criteria for frotteurism:


The patient experiences intense, recurrent, sexual urges and sexually arousing fantasies involving touching and rubbing against a nonconsensual person. Symptoms must be present for at least 6 months.
The patient experiences significant distress or impairment in social, occupational, or other important areas of functioning because of the fantasies, urges, or behaviors, or the patient has acted on the sexual urges.
Frotteurs typically act out their fantasies in crowded places (eg, public transportation vehicles, busy sidewalks), which allows for escape; the frotteur can claim that the touching was accidental. The frotteur rubs his genital area against the (usually female) victim's thighs or buttocks, or the frotteur fondles a woman's genitalia or breasts with his hands. While committing the act, the offender typically fantasizes about an exclusive, caring relationship with the victim.

Most acts occur in perpetrators aged 15-25 years, after which frequency gradually declines. Frotteurism has been noted to be equally common among older, shy, inhibited individuals. Fantasies of frotteuristic behavior without action have been reported as a stimulant to sexual arousal.

Voyeurism

The term voyeurism, from the French word meaning to see, refers to the fairly common desire to view nudity and acts of coition. Differentiating innocent enjoyment of nudity from behavior that is similar but deviant in other circumstances can be difficult.

The DSM-IV-TR diagnostic criteria for voyeurism are as follows:


The patient has recurrent and intense sexual urges and sexually arousing fantasies involving the act of observing an unsuspecting person who is naked, in the process of disrobing, or engaging in sexual activity. Symptoms must be present for at least 6 months.
The patient experiences significant distress or impairment in social, occupational, or other important areas of functioning because of the fantasies, urges, or behaviors.
When severe, the act of peeping constitutes the exclusive form of sexual activity. Onset usually is in persons younger than 15 years, and the disorder tends to be chronic. The wide extent of voyeuristic tendencies in the general population is evidenced in the common desire to indulge in exploitative activities such as live shows and pornography.

Pedophilia

The essential features of this disorder as described by the DSM-IV-TR include the following:


The patient reports recurrent and intense sexually arousing fantasies, sexual urges, or behaviors involving sexual activity with a prepubescent child or children, generally aged 13 years or younger.
Pedophiles must be aged 16 years or older and be at least 5 years older than the victim.
The disorder causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.
The clinician should specify if the person is attracted to males, females, or both; if the acts are limited to incest; and if the patient is attracted to children only (exclusive type) or both children and adults (nonexclusive type).
While female pedophiles are considered to be rare, discrepancies between the numbers of male and female offenders are tied to sexual stereotypes. Masculinity connotes sexual qualities, while femininity connotes maternal qualities and nurturance. When a female pets a child, she is nurturing. When a male pets a child, he is molesting. The majority of men who have had sexual contact with a woman when they were boys viewed it positively rather than negatively. Consequently, these acts were probably unreported. In one study, 16% of college males and 46% of prisoners reported having had sexual contact with older females, and half of the encounters involved intercourse. Mean age of males at the time of sexual contact was 12 years, and the females with whom they were involved were aged 20-30 years.

Many pedophiles have a personal history of unstable parent-child relationships as children and sexual abuse. The majority of pedophiles have a clear sexual preference. The undifferentiated or bisexual group accounts for only 5-25% of pedophiles. Most studies indicate that 60-90% of incidents of abuse involve girls.

Great variation exists among men who use children sexually. One third to one half prefer children as sexual partners. Others are attracted to children but act on their impulses only under stress. Some, who typically are younger than 30 years, are sociosexually underdeveloped, lack age-appropriate experience, and have feelings of shyness and inferiority. Unable to attain adult female contact, they continue prepubescent sexual patterns. Amoral delinquent youths (younger than pedophiles proper), lacking control when aroused, use whoever is close at hand. Patients with the situational type of pedophilia have no special preference for children, although they have sexual contact with children because of convenience or coincidence. Contact typically is brief and nonrecurrent. A residual category of offenders includes people with mental retardation, psychosis, alcoholism, senility, or dementia.

Approximately 37% of sexual assault victims reported to law enforcement agencies were juveniles ( <18 y); 34% of all victims were younger than 12 years. One in 7 victims is younger than 6 years. Forty percent of offenders who victimized children younger than 6 years were juveniles ( <18 y).

Sexual masochism

The essential features of this disorder as described by the DSM-IV-TR include the following:


The patient reports recurrent and intense sexual urges and sexually arousing fantasies involving the act (real, not simulated) of being humiliated, beaten, bound, or otherwise made to suffer. Symptoms must be present for at least 6 months.
The fantasies, urges, or behaviors cause significant distress or impairment in social, occupational, or other important areas of functioning.
Masochistic acts commonly involve a wide range of activities, such as restraint, blindfolding, beating, electrical shock, cutting, piercing, and humiliation (eg, being urinated or defecated on, forced to bark, verbally abused, forced to cross-dress). Some sexual masochists inflict pain through self-mutilation, and some engage in group activity or use services provided by prostitutes.

Hypoxyphilia is a dangerous form of masochism that involves sexual arousal by oxygen deprivation achieved by means of chest compression, noose, ligature, plastic bag, mask, or chemicals. Oxygen deprivation may be accomplished alone or with a partner. Data from the United States, England, Australia, and Canada indicate that 1-2 deaths per million population are reported each year.

Some sexually masochistic males also exhibit fetishism, transvestic fetishism, or sexual sadism. Masochistic sexual fantasies are likely present in childhood. Masochistic activities commonly begin by early adulthood, tend to be chronic, and the same act is generally repeated. Some individuals increase the severity of the act over time, which may lead to injury or death.

In 1926, Sadger observed a common association between homosexuality and masochism. In a 1977 report, Spengler found that 38% of exclusive homosexuals were sadomasochists, which provides some support for Sadger's observation.

Ritualized behavior is a noted feature of masochistic scenes; the slightest deviation from the script may result in failure to achieve the desired result. This feature is also viewed as a mechanism through which the masochist maintains control.

Sexual sadism

The DSM-IV-TR diagnostic criteria for sexual sadism are as follows:


The patient reports recurrent and intense sexual urges and sexually arousing fantasies involving the act (real, not simulated) in which the psychological or physical suffering (including humiliation) of one person is sexually arousing to another person. Symptoms must be present for at least 6 months.
The fantasies, urges, or behaviors cause significant distress or impairment in social, occupational, or other important areas of functioning.
Sadistic fantasies or acts may involve activities such as dominance, restraint, blindfolding, beating, pinching, burning, electrical shock, rape, cutting, stabbing, strangulation, torture, mutilation, or killing. Sadistic sexual fantasies are likely present in childhood. Onset of sadistic activities commonly occurs by early adulthood, and it tends to be chronic.

Some individuals do not increase the severity of their sadistic acts; however, severity of the sadistic acts does usually increase over time. When practiced with nonconsenting partners, the activity is likely to be repeated until the perpetrator is apprehended. When sexual sadism is severe and associated with antisocial personality disorder, victims may be seriously injured or killed.

No clear lines divide sexual sadism and sexual masochism, and the predispositions are often interchangeable. The conditions may coexist in the same individual, sometimes in association with other paraphilias. This relationship is supported by the finding that those who entertain masochistic fantasies also engage in sadistic fantasies. In the context of psychoanalytic theory, Panken in a 1973 publication does not find that the conditions coexist in an individual and claims that the dynamics are different.

Transvestic fetishism

Transvestic fetishism is defined by DSM-IV-TR diagnostic criteria as follows:


The patient is a heterosexual male who has recurrent, intense, sexually arousing fantasies, urges, or behaviors involving cross-dressing. Symptoms must be present for at least 6 months.
These fantasies, urges, or behaviors cause significant distress or impairment in social, occupational, or other important areas of functioning.
If gender dysphoria is present, it should be specified.
Fetishistic transvestism is essentially unheard of in females. Women may cross-dress, but no literature (English) describes cross-dressing females who become sexually excited by the activity.

Other paraphilias

Sexual arousal may be obtained from a wide array of additional behaviors. Some are provided with the assistance of prostitutes, others find willing partners when needed. Other paraphilias include the following:


Scatologia (obscene phone calls)
Necrophilia (corpses)
Partialism (exclusive focus on part of body)
Zoophilia (animals)
Coprophilia (feces)
Klismaphilia (enemas)
Urophilia (urine)


Read more HERE

Botulism

Botulism is an acute neurologic disorder with potentially life-threatening neuroparalysis that is caused by a neurotoxin produced by Clostridium botulinum (CB). The toxin binds irreversibly to the presynaptic membranes of peripheral neuromuscular and autonomic nerve junctions. Toxin binding blocks acetylcholine release, resulting in weakness, flaccid paralysis, and (often) respiratory arrest. Cure occurs following sprouting of new nerve terminals.

The 3 main clinical presentations of botulism include infant, food-borne, and wound. Additionally, because of the potency of the toxin, the possibility of botulism as a bioterrorism agent or biological weapon is a great concern.

Infant botulism (IB) arises from ingested botulism spores that germinate in the intestine and produce toxin. These spores typically come from bee honey or the environment. Most infants fully recover with supportive treatment; the infant mortality rate is less than 1%. Improperly canned or home-prepared foods are common sources of the toxin that can result in food-borne botulism (FBB). Wound botulism (WB) results from contamination of the wound with toxin-producing CB. FBB and WB occur predominantly in adults and are the focus of this article.

CB is an anaerobic gram-positive rod that survives in soil and marine sediment by forming spores. Under anaerobic conditions that permit germination, it synthesizes and releases a potent exotoxin. Microbiologically, the organism stains gram-positive in cultures less than 18 hours old. The organism may stain gram-negative after 18 hours of incubation, potentially complicating attempts at diagnosis. On a molecular weight basis, botulinum toxins are the most potent toxins known.

Eight antigenically distinct CB toxins are known, including A, B, C (alpha), C (beta), D, E, F, and G. Each strain of CB is limited to producing a single toxin type. Types A, B, E, and (rarely) F cause human disease. Toxins A and B are the most potent, and the consumption of small amounts of food contaminated with them has resulted in full-blown disease. During the last 20 years, toxin A has been the most frequent cause of food-borne outbreaks; toxins B and E follow in frequency. In 15% of CB outbreaks, the toxin type is not determined. Toxins C and D cause disease in a variety of animals. Type G toxin has been associated with sudden death but not with neuroparalytic illness. It was isolated from autopsy material from 5 patients in Switzerland in 1977.

Pathophysiology
The mechanism of action involves toxin-mediated blockade of neuromuscular transmission in cholinergic nerve fibers. This is accomplished by either inhibiting acetylcholine release at the presynaptic clefts of the myoneural junctions or by binding acetylcholine itself. Toxins are absorbed from the stomach and small intestine where they are not denatured by digestive enzymes. Subsequently, they are hematogenously disseminated and block neuromuscular transmission in cholinergic nerve fibers. The nervous, gastrointestinal, endocrine, and metabolic systems are predominantly affected. Because the motor end plate responds to acetylcholine, botulinum toxin ingestion results in hypotonia that manifests as descending symmetric flaccid paralysis and is usually associated with gastrointestinal symptoms of nausea, vomiting, and diarrhea. Cranial nerves are affected early in the course of disease. Later complications include paralytic ileus, severe constipation, and urinary retention.

WB results when wounds are contaminated with CB spores. It has occurred (1) after traumatic injury that involved soil contamination, (2) among injection drug users, particularly those who use black-tar heroin, and (3) after cesarean delivery. The wound may appear deceptively benign. Traumatized and devitalized tissue provides an anaerobic medium for the spores to germinate into vegetative organisms and produce neurotoxin, which then disseminates hematogenously. The nervous, endocrine, and metabolic systems are predominantly affected. Symptoms develop after an incubation period of 4-14 days, with a mean of 10 days. The clinical symptoms of WB are similar to those of FBB except that gastrointestinal symptoms (including nausea, vomiting, diarrhea) are uncommon.

Frequency
United States
The frequency is 0.034 cases out of 100,000 population, of which nearly 75% are associated with IB.

FBB incidences total 24 cases per year. WB incidences total 3 cases per year and 3 cases per year from the young adult cohort (aged 18-25 y). IB incidences total 71 cases per year, with a mean age of 3 months. FBB incidence totals 24 cases per year drawn from all age cohorts.

Toxin A is found predominantly west of the Mississippi River. Toxin B is found most commonly in the eastern United States. Toxin E is found in northern latitudes, such as the Pacific Northwest, the Great Lakes region, and Alaska. The native peoples have some of the highest rates of botulism in the world. Toxin E outbreaks frequently are associated with fish products.

International
Human botulism is found worldwide. Spores from organisms producing type A or B toxins are distributed widely in the soil and have been found throughout the world. Toxin type B commonly is found in Europe. Toxin G originally was isolated in Switzerland.

Mortality/Morbidity

Mortality rates vary according to age of the patient and the type of botulism observed. In FBB, a 25% mortality rate exists overall; however, the rate is 10% in patients younger than 20 years. In WB, the mortality rate varies (15-17%); in IB, the mortality rate usually is less than 1%.
The recovery period from botulism often is quite long (30-100 d). Some patients demonstrate residual weakness or autonomic dysfunction for 1 year after the onset of the illness. However, full neurologic recovery is usual. Permanent deficits may occur in those who sustain significant hypoxic insults.

Sex
Males present more frequently with WB than females. Males and females present with FBB in equal numbers.

Age
FBB and WB predominately occur in adults.


Read more HERE

Diabetes Mellitus, Type 1

Diabetes mellitus (DM) is a multisystem disease with both biochemical and anatomical consequences. It is a chronic disease of carbohydrate, fat, and protein metabolism caused by the lack of insulin. In type 1 diabetes, insulin is functionally absent because of the destruction of the beta cells of the pancreas. Type 1 DM occurs most commonly in juveniles but can occur in adults, especially in those in their late 30s and early 40s. Unlike people with type 2 DM, those with type 1 DM generally are not obese and may present initially with diabetic ketoacidosis (DKA).

Pathophysiology
Type 1 DM is a catabolic disorder in which circulating insulin is very low or absent, plasma glucagon is elevated, and the pancreatic beta cells fail to respond to all insulin-secretory stimuli. Patients need exogenous insulin to reverse this catabolic condition, prevent ketosis, decrease hyperglucagonemia, and normalize lipid and protein metabolism.

Type 1 DM is an autoimmune disease. The pancreas shows lymphocytic infiltration and destruction of insulin-secreting cells of the islets of Langerhans, causing insulin deficiency. Approximately 85% of patients have circulating islet cell antibodies, and the majority also have detectable anti-insulin antibodies before receiving insulin therapy. Most islet cell antibodies are directed against glutamic acid decarboxylase (GAD) within pancreatic B cells.

One theory regarding the etiology of type 1 DM is that it results from damage to pancreatic beta cells from an infectious or environmental agent. It triggers the immune system in a genetically susceptible individual to develop an autoimmune response against altered pancreatic beta cell antigens or molecules in beta cells that resemble a viral protein. Currently, autoimmunity is considered the major factor in the pathophysiology of type 1 DM. Prevalence is increased in patients with other autoimmune diseases, such as Graves disease, Hashimoto thyroiditis, and Addison disease. Approximately 95% of patients with type 1 DM have either human leukocyte antigen (HLA)-DR3 or HLA-DR4. HLA-DQs are considered specific markers of type 1 DM susceptibility.

Environmental agents that have been hypothesized to induce an attack on beta cell function include viruses (eg, mumps, rubella, Coxsackie B4), toxic chemicals, exposure to cow's milk in infancy, and cytotoxins.

Recent evidence suggests a role for vitamin D in the pathogenesis and prevention of diabetes mellitus.


Frequency
United States
Roughly 5-15% of all cases of diabetes are type 1 DM. It is the most common metabolic disease of childhood, with a yearly incidence of 15 cases per 100,000 people younger than 18 years. Approximately 1 million Americans have type 1 DM, and physicians diagnose 10,000 new cases every year.


According to the American Diabetes Association, there are 20.8 million children and adults in the United States, or 7% of the population, who have diabetes. While an estimated 14.6 million have been diagnosed, unfortunately, 6.2 million people (or nearly one-third) are undiagnosed. Fifty-four million people are prediabetes status. In people younger than 20 years, 176,500 cases, or 0.22% of all people in this age group, have diabetes. About one in every 400-600 children and adolescents has type 1 DM. Two million adolescents (or 1 in 6 overweight adolescents) aged 12-19 years have prediabetes status. In people aged 20 years or older, 1.5 million new cases of diabetes were diagnosed in 2005.


International
Scandinavia has the highest prevalence rates for type 1 DM (ie, approximately 20% of the total number of people with DM), while China and Japan have the lowest prevalence rates, with less than 1% of all people with diabetes. Some of these differences may relate to definitional issues and the completeness of reporting.

Mortality/Morbidity
Type 1 DM is associated with a high morbidity and premature mortality due to complications. The annual financial cost from diabetes overall exceeds $100 billion, almost $1 of every $7 dollars of US health expenditures in terms of medical care and loss of productivity. Advances in treatment that permit tight glycemic control and control of comorbidities (hyperlipidemia) can greatly reduce the incidence of microvascular and macrovascular complications.

As a result of these complications, people with diabetes have an increased risk of developing ischemic heart disease, cerebral vascular disease, peripheral vascular disease with gangrene of lower limbs, chronic renal disease, reduced visual acuity and blindness, and autonomic and peripheral neuropathy.

Race
Type 1 DM is more common among non-Hispanic whites, followed by African Americans and Hispanic Americans. It is comparatively uncommon among Asians.

Sex
Type 1 DM is more common in men than in women.

Age
Type 1 DM usually starts in children aged 4 years or older, with the peak incidence of onset at age 11-13 years, coinciding with early adolescence and puberty. Also, a relatively high incidence exists in people in their late 30s and early 40s, when it tends to present in a less aggressive manner, ie, early hyperglycemia without ketoacidosis and gradual onset of ketosis.


Read more HERE

Thursday, 31 July 2008

Diabetes Mellitus, Type 1 (pedia)

Diabetes mellitus (DM) is a chronic metabolic disorder caused by an absolute or relative deficiency of insulin, an anabolic hormone. Insulin is produced by the beta cells of the islets of Langerhans located in the pancreas, and the absence, destruction, or other loss of these cells results in type 1 diabetes (insulin-dependent diabetes mellitus [IDDM]). Most children with diabetes have IDDM and a lifetime dependence on exogenous insulin.

Type 2 diabetes (non–insulin-dependent diabetes mellitus [NIDDM]) is a heterogeneous disorder. Most patients with NIDDM have insulin resistance, and their beta cells lack the ability to overcome this resistance. Although this form of diabetes was previously uncommon in children, in some, countries 20% or more of new patients with diabetes in childhood and adolescence have NIDDM, a change associated with increased rates of obesity. Other patients may have inherited disorders of insulin release leading to maturity onset diabetes of the young (MODY).

This chapter addresses only IDDM.

Pathophysiology
Insulin is essential to process carbohydrates, fat, and protein. Insulin reduces blood glucose levels by allowing glucose to enter muscle cells and by stimulating the conversion of glucose to glycogen (glycogenesis) as a carbohydrate store. Insulin also inhibits the release of stored glucose from liver glycogen (glycogenolysis) and slows the breakdown of fat to triglycerides, free fatty acids, and ketones. It also stimulates fat storage. Additionally, insulin inhibits the breakdown of protein and fat for glucose production (gluconeogenesis) in both liver and kidneys.

Hyperglycemia (ie, random blood glucose concentration more than 200 mg/dL or 11 mmol/L) results when insulin deficiency leads to uninhibited gluconeogenesis and prevents the use and storage of circulating glucose. The kidneys cannot reabsorb the excess glucose load, causing glycosuria, osmotic diuresis, thirst, and dehydration. Increased fat and protein breakdown leads to ketone production and weight loss. Without insulin, a child with IDDM wastes away and eventually dies from diabetic ketoacidosis (DKA).

An excess of insulin prevents the release of glucose into the circulation and results in hypoglycemia (blood glucose concentrations of <60 mg/dL or 3.5 mmol/L). Glucose is the sole energy source for erythrocytes, kidney medulla, and the brain.


Frequency
United States
Overall incidence is approximately 15 cases per 100,000 individuals annually and probably increasing. An estimated 3 children out of 1000 develop IDDM by age 20 years.

International
DM exhibits wide geographic variation in incidence and prevalence. Annual incidence varies from 0.61 cases per 100,000 persons in China, to 41.4 cases per 100,000 in Finland. Substantial variations exist between nearby countries with differing lifestyles, such as Estonia and Finland, and between genetically similar populations such as those in Iceland and Norway. Even more striking are the differences in incidence between mainland Italy (8.4/100,000) and the Island of Sardinia (36.9/100,000). These variations strongly support the importance of environmental factors in the development of IDDM. Most countries report that incidence rates have at least doubled or more in the last 20 years. Incidence appears to increase with distance from the equator.

Mortality/Morbidity
Information on mortality rates is difficult to ascertain without complete national registers of childhood diabetes, although age-specific mortality is probably double that of the general population. Particularly at risk are children aged 1-4 years who may die with DKA at the time of diagnosis. Adolescents are also a high-risk group. Most deaths result from delayed diagnosis or neglected treatment and subsequent cerebral edema during treatment for DKA, although untreated hypoglycemia also causes some deaths. Unexplained death during sleep may also occur.

IDDM complications are comprised of 3 major categories: acute complications, long-term complications, and complications caused by associated autoimmune diseases.


Acute complications reflect the difficulties of maintaining a balance between insulin therapy, dietary intake, and exercise. Acute complications include hypoglycemia, hyperglycemia, and DKA.
Long-term complications arise from the damaging effects of prolonged hyperglycemia and other metabolic consequences of insulin deficiency on various tissues. While long-term complications are rare in childhood, maintaining good control of diabetes is important to prevent complications from developing in later life. The likelihood of developing complications appears to depend on the interaction of factors such as metabolic control, genetic susceptibility, lifestyle (eg, smoking, diet, exercise), pubertal status, and gender.Long-term complications include the following:
Retinopathy
Cataracts
Hypertension
Progressive renal failure
Early coronary artery disease
Peripheral vascular disease
Neuropathy, both peripheral and autonomic
Increased risk of infection
Associated autoimmune diseases are common with IDDM, particularly in children who have the human leukocyte antigen DR3 (HLA-DR3). Some conditions may precede development of diabetes; others may develop later. As many as 20% of children with diabetes have thyroid autoantibodies.

Race

Different environmental effects on IDDM development complicate the influence of race, but racial differences clearly exist.
Whites have the highest reported incidence of IDDM; Chinese have the lowest.
IDDM is 1.5 times more likely to develop in American whites than in American blacks or Hispanics.
Current evidence suggests that when immigrants from an area with low incidence move to an area with higher incidence, their IDDM rates tend to increase toward the higher level.

Sex

The influence of sex varies with the overall incidence rates.
Males are at greater risk in regions of high incidence, particularly older males, whose incidence rates often show seasonal variation.
Females appear to be at a greater risk in low-incidence regions.

Age

Generally, incidence rates increase with age until mid-puberty then decline after puberty, but IDDM can occur at any age. Onset in the first year of life, though unusual, can occur and must be considered in any infant or toddler, because these children have the greatest risk for mortality if diagnosis is delayed. Their symptoms may include the following:
Severe monilial diaper/napkin rash
Unexplained malaise
Poor weight gain or weight loss
Increased thirst
Vomiting and dehydration, with a constantly wet napkin/diaper
Where prevalence rates are high, a bimodal variation of incidence has been reported that shows a definite peak in early childhood (ie, 4-6 y) and a second, much greater peak of incidence during early puberty (ie, 10-14 y).


Read further HERE

Wednesday, 30 July 2008

Mesenteric Ischemia

Mesenteric ischemia is a relatively rare disorder seen in the emergency department (ED); however, it is an important diagnosis to make because of its high mortality rate. Vague and nonspecific clinical findings and limitations of diagnostic studies make the diagnosis a significant challenge. Moreover, delays in diagnosis lead to increased mortality rates. Despite recent advances in diagnosis and treatment, mortality rates continue to remain high.

Pathophysiology
Mesenteric ischemia is caused by decreased intestinal blood flow that can be caused by a number of mechanisms. Decreased intestinal blood flow results in ischemia and subsequent reperfusion damage at the cellular level that may progress to the development of mucosal injury, tissue necrosis, and metabolic acidosis.

The blood supply to the intestine is derived predominantly from 3 major gastrointestinal arteries that arise from the abdominal aorta: the celiac axis, the superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA). The intestine has significant collateral circulation at all levels that allows for some protection from ischemia and is able to compensate for approximately a 75% acute reduction in mesenteric blood flow for up to 12 hours, without substantial injury.

The pathophysiology of intestinal ischemia can be divided into arterial and venous etiologies and acute and chronic ischemia. The vast majority of cases are secondary to arterial causes. All diseases and conditions that affect arteries, including atherosclerosis, arteritis, aneurysms, arterial infections, dissections, arterial emboli, and thrombosis, are reported to occur in the intestinal arteries.

Acute mesenteric ischemia (AMI) can be further divided into embolic, thrombotic, or nonocclusive causes.


Arterial embolism
Arterial embolism accounts for approximately one third of acute cases of AMI.
Emboli to the mesenteric arteries are usually from a dislodged cardiac thrombus.
The SMA is most commonly affected with the IMA rarely affected due to its small caliber.
Arterial thrombosis
Arterial thrombosis accounts for approximately one third of acute cases of AMI.
It is usually due to acute worsening of ischemia in patients who have preexisting atherosclerosis of the mesenteric arteries.
Thrombosis often involves at least 2 of the major splanchnic vessels.
Nonocclusive etiology
Nonocclusive etiology accounts for approximately one third of acute cases of AMI.
The primary mechanism is severe and prolonged intestinal vasoconstriction.
The most common setting is severe systemic illness with systemic shock usually secondary to reduced cardiac output.
Intestinal vasospasm has also been seen to occur in cocaine ingestion, ergot poisoning, digoxin use, and with alpha-adrenergic agonists.
A small proportion of cases are from venous thrombosis, seen mostly in patients with hypercoagulable states.
Venous thrombosis of the visceral vessels may precipitate an acute ischemic event as compromised venous return leads to interstitial swelling of the bowel wall, with subsequent impedance of arterial flow and eventual tissue necrosis.

Chronic mesenteric ischemia (CMI) usually results from long-standing atherosclerotic disease of 2 or more mesenteric vessels. Other nonatheromatous causes of CMI include the vasculitides such as Takayasu arteritis. Symptoms are caused by the gradual reduction in blood flow to the intestine that occurs during eating since total blood flow to the intestine can increase by 15% during meals.

Frequency
United States
AMI is involved in up to 0.1% of all hospital admissions, although this number is likely to rise as the population ages.

Mortality/Morbidity

Mortality rates are high and range from 60-100% depending on the source of obstruction. Early and aggressive diagnosis and treatment has been shown to significantly decrease the mortality rate if the diagnosis is made prior to the development of peritonitis.
One report of 21 patients with SMA embolus, intestinal viability was achieved in 100% of patients before diagnosis if the duration of symptoms was less than 12 hours, in 56% if it was between 12 and 24 hours, and in only 18% if symptoms were more than 24 hours in duration.
Another study found that even at hospital centers with angiography available 24 hours, mortality rates still were approximately 70%.

Sex
No sex predilection exists.

Age
Mesenteric ischemia is generally a disease of the older population, with the typical age of onset being older than 60 years; however, with risk factors and other predisposing factors, it may be seen in younger patients.


Read more HERE

Aortic Stenosis

Aortic stenosis (AS) is the obstruction of blood flow across the aortic valve. AS has several etiologies: congenital unicuspid or bicuspid valve, rheumatic fever, and degenerative calcific changes of the valve.

Pathophysiology
When the aortic valve becomes stenotic, resistance to systolic ejection occurs and a systolic pressure gradient develops between the left ventricle and the aorta. Stenotic aortic valves have a decreased aperture that leads to a progressive increase in left ventricular systolic pressure. This leads to pressure overload in the left ventricle, which, over time, causes an increase in ventricular wall thickness (ie, concentric hypertrophy). At this stage, the chamber is not dilated and ventricular function is preserved, although diastolic compliance may be affected.

Eventually, however, the left ventricle dilates. This, coupled with a decrease in compliance, is associated with an increase in left ventricular end-diastolic pressure, which is increased further by a rise in atrial systolic pressure. A sustained pressure overload eventually leads to myocardial decompensation. The contractility of the myocardium diminishes, which leads to a decrease in cardiac output. The elevated left ventricular end-diastolic pressure causes a corresponding increase in pulmonary capillary arterial pressures and a decrease in ejection fraction and cardiac output. Ultimately, congestive heart failure (CHF) develops.

Frequency
United States
Aortic stenosis is a relatively common congenital cardiac defect. Incidence is 4 in 1000 live births.


Mortality/Morbidity
Sudden cardiac death occurs in 3-5% of patients with AS. Adults with AS have a 9% mortality rate per year. Once symptoms develop, the incidence of sudden death increases to 15-20%, with average survival duration of less than 5 years. Patients with exertional angina or syncope survive an average of 3 years. After the development of left ventricular failure, life expectancy is slightly greater than 1 year.

Sex
Among children, 75% of cases of AS are in males.

Age
AS usually is not detected until individuals are school aged. AS exists in up to 2% of those who are younger than 70 years. The etiology of AS in those aged 30-70 years can be rheumatic disease or calcification of a congenital bicuspid valve. In those older than 70 years, degenerative calcification is the primary cause of AS. Among people older than 75 years, 3% have critical AS.


Read more HERE

ART

Angina Pectoris

Angina pectoris (AP) represents the clinical syndrome occurring when myocardial oxygen demand exceeds supply. The term is derived from Latin; the literal meaning is "the choking of the chest;" angere, meaning "to choke" and pectus, meaning "chest." The first English-written account of recurrent angina pectoris was by English nobleman Edward Hyde, Earl of Clarendon. He described his father as having, with exertion, "a pain in the left arm…so much that the torment made him pale".1 The first description of angina as a medical disorder came from William Heberden. Heberden, a prodigious physician, made many noteworthy contributions to medicine during his career. He presented his observations on "dolor pectoris" to the Royal College of Physicians in 1768. Much of his classic description retains its validity today.2

Angina pectoris has a wide range of clinical expressions. The symptoms most often associated to angina pectoris are substernal chest pressure or tightening, frequently with radiating pain to the arms, shoulders, or jaw. The symptoms may also be associated with shortness of breath, nausea, or diaphoresis. Symptoms stem from inadequate oxygen delivery to myocardial tissue. No definitive diagnostic tools that capture all patients with angina pectoris exist. This, combined with its varied clinical expression, makes angina pectoris a distinct clinical challenge to the emergency physician. The disease state can manifest itself in a variety of forms:

Stable angina pectoris is classified as a reproducible pattern of anginal symptoms that occur during states of increased exertion.
Unstable angina pectoris (UA) manifests either as an increasing frequency of symptoms or as symptoms occurring at rest.
Prinzmetal angina or variant angina occurs as a result of transient coronary artery spasms. These spasms can occur either at rest or with exertion. Unlike stable or unstable angina, no pathological plaque or deposition is present within the coronary arteries that elicits the presentation. On angiography, the coronary arteries are normal in appearance.
Cardiac syndrome X occurs when a patient has all of the symptoms of angina pectoris without coronary artery disease or spasm.

Pathophysiology
The past 2 decades has greatly expanded our overall understanding of the pathophysiology of myocardial ischemic syndromes. The primary dysfunction in angina pectoris is decreased oxygen delivery to myocardial muscle cells. The 2 predominant mechanisms by which delivery is impaired appear to be coronary artery narrowing and endothelial dysfunction. Any other mechanism that affects oxygen delivery can also precipitate symptoms.

Extracardiac causes of angina include, but are by no means limited to, anemia, hypoxia, hypotension, bradycardia, carbon monoxide exposure, and inflammatory disorders.3 The end result is a shift to anaerobic metabolism in the myocardial cells. This is followed by a stimulation of pain receptors that innervate the heart. These pain receptors ultimately are referred to afferent pathways, which are carried in multiple nerve roots from C7 through T4. The referred/radiating pain of angina pectoris is believed to occur because these afferent pathways also carry pain fibers from other regions (eg, the arm, neck, and shoulders).

Coronary artery narrowing

Coronary artery narrowing appears to be the etiology of cardiac ischemia in the preponderance of cases. This has clinical significance when atherosclerotic disease diminishes or halts blood flow through the coronary arterial circulation, interfering with normal laminar blood flow. The significance of even a small change in the diameter of a blood vessel can be profound. The Poiseuille law predicts this outcome—the rate of flow is decreased exponentially by any change in the radius of the lumen. As with a smaller pediatric airway, even relatively minute changes in diameter have dramatic consequences in flow rates. Thus, when a lumen is narrowed by one fifth, the flow rate is decreased by about one half. This predicts that even a small change in a coronary artery plaque size can affect the oxygenation through that vessel's territory.

The epicardial vessel, where atherosclerosis often takes place, has the capacity to dilate via autoregulatory mechanisms to respond to increased demand. Angina occurs as this compensatory mechanism is overwhelmed either by large plaques (typically considered 70% or greater obstruction) or by significantly increased myocardial demand.4

Endothelial factors

Endothelial factors also play an important role in angina pectoris. During sympathetic stimulation, the endothelium is subjected to mediators of both vasoconstriction and vasodilatation. Alpha-agonists (catecholamines) directly cause vasoconstriction, while endothelial nitrous oxide synthase creates nitrous oxide (NO), which counteracts this constricting force via vasodilatation.

In the diseased coronary artery, NO production is reduced or absent. In this setting, the catecholamine drive can overwhelm the autoregulatory mechanisms. In addition, the endothelium of the plaque-laden artery may, in itself, be dysfunctional. This limits the ability of the intra-arterial endothelium to produce mediators, which, in a healthy artery, would protect against further vasoconstriction, assist dilatation, and provide protection from platelet aggregation. Small lesions in these vessels may produce incompletely obstructing aggregates of platelets. This would further impede flow through the affected vessel.4

In the diseased heart, these 2 factors, coronary artery narrowing and endothelial dysfunction, synergistically result in reduced oxygen delivery to the myocardium. The net result is angina pectoris.

Extrinsic factors

Extrinsic factors can also play a role in specific circumstances. The oxygen-carrying capacity of blood is based on a number of factors. The most important of which is the amount of hemoglobin. Any alteration in the ability of blood to carry oxygen can precipitate angina. Anemia of any degree can result in anginal symptoms. Given a scenario where demand is increased, such as climbing a flight of stairs, increased stress, or even sexual intercourse, the anginal symptoms may appear.5 Abnormal hemoglobin, such as methemoglobin, carboxyhemoglobin, or any of a number of hemoglobinopathies, creates an environment at greater risk for precipitating angina.

Other extrinsic factors that affect hemoglobin formation, such as lead poisoning or iron-deficiency states, also lead to a similar decrease in oxygen-carrying capacity. Any mechanism that impedes oxygen delivery to the red blood cells has a similar effect. Therefore, any number of pulmonary causes, such as pulmonary embolism, pulmonary fibrosis or scarring, pneumonia, or congestive heart failure, can exacerbate angina. A decreased oxygen environment, such as travel to a higher elevation, has similar consequences due to the decrease in concentration of atmospheric oxygen.

Variant angina

The etiology of variant angina is currently not well understood. Research suggests that inflammatory mediators may result in focal coronary artery vasospasm. Another possibility is that perfusion is decreased through microvascular circulation. Spasm or intermittent narrowing of this microscopic lumen may result in transient areas of hypoperfusion and oxygen deprivation.6

Syndrome X

Syndrome X is the triad of angina pectoris, a positive ECG stress test result, and a normal coronary angiogram. The pathophysiology of this disease is not well understood. Many theories exist as to the underlying pathology. Decreased oxygenation of the underlying myocardium may be the result of impaired vasodilatation, dysfunctional smooth muscle cells, poor or deficient microvascular circulation, or even structural problems on a cellular level (eg, an inappropriately functioning sodium ion channel).6


Frequency
United States

An estimated 6,500,000 people in the United States experience angina pectoris.

Each year 400,000 new cases of angina pectoris develop.


Mortality/Morbidity
More than 479,000 people died from coronary heart disease (both angina and myocardial infarction) in 2003.

The estimated direct and indirect cost for Americans with coronary heart disease in 2006 was $142.5 billion.


Race

The Centers for Disease Control and Prevention (CDC) note that the prevalence of angina and/or coronary heart disease is highest in Hispanics followed by whites and black non-Hispanics (5%, 4.2%, 3.7%, respectively). This information includes the 50 US states, the District of Columbia, Puerto Rico, and the US Virgin Islands.7


Sex
According to National Health and Nutrition Examination Survey (NHANES) data, the age-adjusted prevalence of self-reported angina appears to be higher in woman than in men. Although 2005 CDC data suggest that men (5.5%) have a higher prevalence of angina and/or coronary heart disease than women (3.4%).7


Age
The incidence of new and recurrent angina increases with age but then declines at around 85 years.

Statistics from American Heart Association and Centers for Disease Control and Prevention.

Read more HERE

Tuesday, 29 July 2008

Allergic Rhinitis

Rhinitis is defined as inflammation of the nasal membranes1 and is characterized by a symptom complex that consists of any combination of the following: sneezing, nasal congestion, nasal itching, and rhinorrhea. The eyes, ears, sinuses, and throat can also be involved. Allergic rhinitis is the most common cause of rhinitis. It is an extremely common condition, affecting approximately 20% of the population. While allergic rhinitis is not a life-threatening condition, complications can occur and the condition can significantly impair quality of life, which leads to a number of indirect costs. The total direct and indirect cost of allergic rhinitis was recently estimated to be $5.3 billion per year.

Pathophysiology
Allergic rhinitis involves inflammation of the mucous membranes of the nose, eyes, eustachian tubes, middle ear, sinuses, and pharynx. The nose invariably is involved, and the other organs are affected in certain individuals. Inflammation of the mucous membranes is characterized by a complex interaction of inflammatory mediators but ultimately is triggered by an immunoglobulin E (IgE)–mediated response to an extrinsic protein.

The tendency to develop allergic, or IgE-mediated, reactions to extrinsic allergens (proteins capable of causing an allergic reaction) has a genetic component. In susceptible individuals, exposure to certain foreign proteins leads to allergic sensitization, which is characterized by the production of specific IgE directed against these proteins. This specific IgE coats the surface of mast cells, which are present in the nasal mucosa. When the specific protein (eg, a specific pollen grain) is inhaled into the nose, it can bind to the IgE on the mast cells, leading to immediate and delayed release of a number of mediators.

The mediators that are immediately released include histamine, tryptase, chymase, kinins, and heparin. The mast cells quickly synthesize other mediators, including leukotrienes and prostaglandin D2. These mediators, via various interactions, ultimately lead to the symptoms of rhinorrhea (ie, nasal congestion, sneezing, itching, redness, tearing, swelling, ear pressure, postnasal drip). Mucous glands are stimulated, leading to increased secretions. Vascular permeability is increased, leading to plasma exudation. Vasodilation occurs, leading to congestion and pressure. Sensory nerves are stimulated, leading to sneezing and itching. All of these events can occur in minutes; hence, this reaction is called the early, or immediate, phase of the reaction.

Over 4-8 hours, these mediators, through a complex interplay of events, lead to the recruitment of other inflammatory cells to the mucosa, such as neutrophils, eosinophils, lymphocytes, and macrophages. This results in continued inflammation, termed the late-phase response. The symptoms of the late-phase response are similar to those of the early phase, but less sneezing and itching and more congestion and mucus production tend to occur. The late phase may persist for hours or days.

Systemic effects, including fatigue, sleepiness, and malaise, can occur from the inflammatory response. These symptoms often contribute to impaired quality of life.

Frequency
United States
Allergic rhinitis affects approximately 40 million people in the United States. Recent US figures suggest a 20% cumulative prevalence rate.

International
Scandinavian studies have demonstrated a cumulative prevalence rate of 15% in men and 14% in women. The prevalence of allergic rhinitis may vary within and among countries. This may be due to geographic differences in the types and potency of different allergens and the overall aeroallergen burden.

Mortality/Morbidity
While allergic rhinitis itself is not life-threatening (unless accompanied by severe asthma or anaphylaxis), morbidity from the condition can be significant. Allergic rhinitis often coexists with other disorders, such as asthma, and may be associated with asthma exacerbations. It is also associated with otitis media, eustachian tube dysfunction, sinusitis, nasal polyps, allergic conjunctivitis, and atopic dermatitis. Allergic rhinitis may also contribute to learning difficulties, sleep disorders, and fatigue.



A number of complications that can lead to increased morbidity or even mortality can occur secondary to allergic rhinitis. Possible complications include otitis media, eustachian tube dysfunction, acute sinusitis, and chronic sinusitis.
Allergic rhinitis can be associated with a number of comorbid conditions, including asthma, atopic dermatitis, and nasal polyps. Evidence now suggests that uncontrolled allergic rhinitis can actually worsen the inflammation associated with asthma or atopic dermatitis. This could lead to further morbidity and even mortality.
Allergic rhinitis can frequently lead to significant impairment of quality of life. Symptoms such as fatigue, drowsiness (due to the disease or to medications), and malaise can lead to impaired work and school performance, missed school or work days, and traffic accidents. The overall cost (direct and indirect) of allergic rhinitis was recently estimated to be $5.3 billion per year.

Race
Allergic rhinitis occurs in persons of all races. Prevalence of allergic rhinitis seems to vary among different populations and cultures, which may be due to genetic differences, geographic factors or environmental differences, or other population-based factors.

Sex
In childhood, allergic rhinitis is more common in boys than in girls, but in adulthood, the prevalence is approximately equal between men and women.

Age
Onset of allergic rhinitis is common in childhood, adolescence, and early adult years, with a mean age of onset 8-11 years, but allergic rhinitis may occur in persons of any age. In 80% of cases, allergic rhinitis develops by age 20 years. The prevalence of allergic rhinitis has been reported to be as high as 40% in children, subsequently decreasing with age. In the geriatric population, rhinitis is less commonly allergic in nature.


Read further HERE

Cholera

The word cholera is derived from a Greek term that means "flow of bile." Cholera is caused by Vibrio cholerae, the most feared epidemic diarrheal disease because of its severity. Dehydration and death can occur within hours of infection.

Robert Koch discovered V cholerae in 1883 during an outbreak in Egypt. The organism is a comma-shaped, gram-negative aerobic bacillus whose size varies from 1-3 µm in length by 0.5-0.8 µm in diameter. Its antigenic structure consists of a flagellar H antigen and a somatic O antigen. The differentiation of the latter allows for separation into pathogenic and nonpathogenic strains. V cholerae O1 and V cholerae O139 are associated with epidemic cholera. V cholerae O1 is classified into 2 major biotypes: classic and El Tor. Currently, El Tor is the predominant cholera pathogen. Organisms in both biotypes are subdivided into serotypes according to the structure of the O antigen, as follows:

Serotype Inaba - O antigens A and C
Serotype Ogawa - O antigens A and B
Serotype Hikojima - O antigens A, B, and C

Pathophysiology
The infectious dose of bacteria required to cause clinical disease varies by the mode of administration. If ingested with water, the infectious dose is 103-106 organisms. When ingested with food, fewer organisms (102-104 organisms) are required to produce disease.

The use of antacids, histamine receptor blockers, and proton pump inhibitors increases the risk of cholera infection and predisposes patients to more severe disease as a result of reduced gastric acidity. The same applies to patients with chronic gastritis secondary to Helicobacter pylori infection or those who have undergone a gastrectomy.

V cholerae O1 and V cholerae O139 cause clinical disease by producing an enterotoxin that promotes the secretion of fluid and electrolytes into the lumen of the small intestine. The enterotoxin is a protein molecule composed of 5 B subunits and 2 A subunits. The B subunits are responsible for binding to a ganglioside (monosialosyl ganglioside, GM1) receptor located on the surface of the cells that line the intestinal mucosa.

The activation of the A1 subunit by adenylate cyclase is responsible for the net increase in cyclic adenosine monophosphate (cAMP). cAMP blocks the absorption of sodium and chloride by the microvilli and promotes the secretion of chloride and water by the crypt cells. The result is watery diarrhea with electrolyte concentrations isotonic to those of plasma.

Fluid loss originates in the duodenum and upper jejunum; the ileum is less affected. The colon is usually in a state of absorption because it is relatively insensitive to the toxin. However, the large volume of fluid produced in the upper intestine overwhelms the absorptive capacity of the lower bowel, resulting in severe diarrhea.

The enterotoxin acts locally and does not invade the intestinal wall. As a result, few neutrophils are found in the stool.


Frequency
United States

Among the millions of Americans who travel to endemic areas in foreign countries, only 42 imported cases of cholera were reported from 1965-1991. However, in August 1986, 4 cases of cholera were acquired in Louisiana and 1 case was acquired in Florida. These patients were hospitalized with severe diarrhea and had stool cultures that yielded toxigenic V cholerae O1 Inaba. Although the vehicle of transmission was not specifically identified, the patients had consumed seafood within 5 days prior to symptom onset. Toxigenic V cholerae O1 El Tor Inaba appears to have an environmental reservoir on the US Gulf Coast.

Sixty-one cases of cholera were reported from January 1, 1995, through December 31, 2000, in 18 states and 2 US territories. Thirty-seven were travel-associated cases; the other 24 cases were acquired in the United States.1 Individuals living in the United States most often acquire cholera through travel to cholera-endemic areas or through consumption of undercooked seafood from the Gulf Coast or foreign waters.

In 2005, 12 cases were reported to the World Health Organization (WHO) and, of these, 8 were imported.


International

Since 1817, 7 cholera pandemics have occurred. The first 6 occurred from 1817-1923 and were probably the result of V cholerae O1 of the classic biotype. The pandemics originated in Asia, with subsequent spread to Europe and the Americas.

The seventh pandemic was caused by V cholerae O1 El Tor, which was first isolated in Egypt in 1905. The pandemic originated from the Celebes Islands, Indonesia, in 1961; this pandemic affected more countries and continents than the previous 6 pandemics. The last extension of this pandemic was into Latin America. The total number of cases officially reported from 1997 through March 26, 1998, was 120,867; 89% of these cases were reported in Africa.

In 2002, all regions of the world continued to report cholera caused by V cholerae O1 El Tor; that year, 142,311 cases and 4564 deaths were reported to the WHO by 52 countries. Compared with 2001, the number of reported cases almost doubled.

Between 2002 and 2004, the number of cases reported to the WHO decreased worldwide. In 2005, however, the number reported increased 30% to a total of 131,943 cases in 52 countries.

In October 1992, an epidemic of cholera emerged from Madras, India, as a result of a new serogroup, O139 (also known as Bengal). This Bengal strain has now spread throughout Bangladesh and India and into neighboring countries in Asia. Some experts regard this as an eighth pandemic. Thus far, 11 countries in Southeast Asia have reported isolation of this Vibrio serogroup.


Mortality/Morbidity
If untreated, the disease rapidly results in dehydration and can result in death in more than 50% of infected individuals. The mortality rate is increased in pregnant women and children.


Age
People of all ages are susceptible, although infants are protected through maternally transmitted antibodies during breastfeeding. An attack of the classic biotype of V cholerae usually protects against recurrent infection by either biotype, but El Tor cholera does not protect against further attacks.


Read further HERE

Wednesday, 16 July 2008

Cardiac Cirrhosis

Background
Cardiac cirrhosis (congestive hepatopathy) includes a spectrum of hepatic derangements that occur in the setting of right-sided heart failure. Clinically, the signs and symptoms of congestive heart failure (CHF) dominate the disorder. Unlike cirrhosis caused by chronic alcohol use or viral hepatitis, the effect of cardiac cirrhosis on overall prognosis is unknown. Because of this, treatment is aimed at managing the patient's underlying heart failure.

Distinguish cardiac cirrhosis from ischemic hepatitis. The latter condition may involve massive hepatocellular necrosis caused by sudden cardiogenic shock or other hemodynamic collapse. Typically, sudden and dramatic serum hepatic transaminase elevations lead to its discovery. Although cardiac cirrhosis and ischemic hepatitis arise from distinct underlying cardiac lesions (right-sided heart failure in the former and left-sided failure in the latter), in clinical practice they may present together.

Despite its name, cardiac cirrhosis rarely satisfies strict pathologic criteria for cirrhosis. The terms congestive hepatopathy and chronic passive liver congestion are more accurate, but the name cardiac cirrhosis has become convention.

Pathophysiology
Decompensated right ventricular or biventricular heart failure causes transmission of elevated central venous pressures directly to the liver via the inferior vena cava and hepatic veins. At a cellular level, venous congestion impedes efficient drainage of sinusoidal blood flow into terminal hepatic venules. Sinusoidal stasis results in accumulation of deoxygenated blood, parenchymal atrophy, necrosis, collagen deposition, and, ultimately, fibrosis.

A separate theory proposes that cardiac cirrhosis is not simply a response to chronically increased pressure and sinusoidal stasis. That intrahepatic vascular lesions are confined to areas of the liver with higher fibrotic burden suggests that cardiac cirrhosis requires a higher grade of vascular obstruction, such as intrahepatic thrombosis, for its development. The theory proposes that thrombosis of sinusoids and terminal hepatic venules propagates to medium-sized hepatic veins and to portal vein branches, resulting in parenchymal extinction and fibrosis.

Frequency
United States
Cardiac cirrhosis rarely occurs in the United States. Its true prevalence is difficult to estimate, since the disease typically remains subclinical and undiagnosed. The incidence of cardiac cirrhosis at autopsy has decreased significantly over the past several decades. This may be due to lower rates of uncorrected rheumatic heart disease and constrictive pericardial disease.

Mortality/Morbidity
The effect of cardiac cirrhosis on mortality and morbidity rates is unknown. The severity of the patient's underlying cardiac disease, which is typically advanced and chronic, is the major determinant of overall outcome.

Sex
Comparative sex data for cardiac cirrhosis do not exist. However, because CHF is more common in men than women in the United States, the same is likely for cardiac cirrhosis.

Age
No published data exist. However, the prevalence of cardiac cirrhosis in the United States, like that of CHF, almost certainly increases with age.

Read more HERE

Tuesday, 1 July 2008

Adrenal Carcinoma

Adrenocortical cancers (ACs) are uncommon malignancies that can have protean clinical manifestations. Adrenocortical masses are common; autopsy studies show that approximately 5-15% of the general adult population may have adrenal incidentalomas. Adrenal incidentalomas are biochemically and clinically asymptomatic adrenal masses found incidentally as a result of unrelated imaging investigations such as abdominal CT or MRI scans. Findings from abdominal CT scans suggest that the prevalence rate is 1-5%. Only a small number of adrenal tumors are functional and an even smaller number (approximately 1%) are malignant.
Regardless of size, approximately 1 per 1500 adrenal tumors is malignant. The evaluation of these incidentalomas, therefore, focuses on (1) identifying functional masses and treating them appropriately (including surgical removal); (2) identifying adrenal carcinomas early, with the intent of attempting complete surgical extirpation; and (3) reassuring the patients who do not fit either of these classes and arranging for their subsequent follow-up.
Although the means of identifying ACs from this subpopulation still are controversial, virtually all authorities agree about removing all nonfunctional adrenal tumors larger than or equal to 6 cm because of the significant potential cancer risk. Authorities also generally agree that nonfunctional adrenal tumors (£3 cm) have a very low probability of being adrenal cancer; therefore, they can be removed safely.
The management strategy for adrenal masses larger than 3 cm and less than 6 cm is disputed. Some authorities suggest lowering the threshold for surgical removal of nonfunctional masses from 6 cm to 4-5 cm. Others individualize the follow-up of these patients depending on their clinical status, CT scan characteristics, and age. Particularly important is the fact that these criteria do not apply to children, who generally have smaller ACs. A review of the available data suggests that the incidence rate of malignancy is small Frequency
International
AC tumors are uncommon. The incidence is approximately 0.6-1.67 cases per million persons per year. Some reports suggest an inordinately high frequency (up to 10-fold higher) of cases among children in southern Brazil, for unknown reasons. Overall, AC accounts for 0.02-0.2% of all cancer-related deaths; therefore, it is relatively rare.
Race
AC has no specific racial predilection.
Sex
The female-to-male ratio is approximately 2.5-3:1. Male patients tend to be older and have a worse overall prognosis than female patients. Female patients are more likely than male patients to have an associated endocrine syndrome. Nonfunctional ACs are distributed equally between the sexes.
Age
AC occurs in 2 major peaks: in the first decade of life and again in the fourth to fifth decades. Approximately 75% of the children with AC are younger than 5 years. Functional tumors also are more common in children, while nonfunctional tumors are more common in adults.

Read more HERE

Sunday, 29 June 2008

Hydrocephalus

Hydrocephalus can be defined broadly as a disturbance of formation, flow, or absorption of cerebrospinal fluid (CSF) that leads to an increase in volume occupied by this fluid in the central nervous system (CNS). This condition also could be termed a hydrodynamic disorder of CSF. Acute hydrocephalus occurs over days, subacute over weeks, and chronic over months or years. Conditions such as cerebral atrophy and focal destructive lesions also lead to an abnormal increase of CSF in CNS. In these situations, loss of cerebral tissue leaves a vacant space that is filled passively with CSF. Such conditions are not the result of a hydrodynamic disorder and therefore are not classified as hydrocephalus. An older misnomer used to describe these conditions was hydrocephalus ex vacuo.

Normal pressure hydrocephalus (NPH) describes a condition that rarely occurs in patients younger than 60 years. Enlarged ventricles and normal CSF pressure at lumbar puncture (LP) in the absence of papilledema led to the term NPH. However, intermittent intracranial hypertension has been noted during monitoring of patients in whom NPH is suspected, usually at night. The classic Hakim triad of symptoms includes gait apraxia, incontinence, and dementia. Headache is not a typical symptom in NPH.

Benign external hydrocephalus is a self-limiting absorption deficiency of infancy and early childhood with raised intracranial pressure (ICP) and enlarged subarachnoid spaces. The ventricles usually are not enlarged significantly, and resolution within 1 year is the rule.

Communicating hydrocephalus occurs when full communication exists between the ventricles and subarachnoid space. It is caused by overproduction of CSF (rarely), defective absorption of CSF (most often), or venous drainage insufficiency (occasionally).

Noncommunicating hydrocephalus occurs when CSF flow is obstructed within the ventricular system or in its outlets to the arachnoid space, resulting in ventricular/subarachnoid space noncommunication.

Obstructive hydrocephalus results from obstruction of the flow of CSF (intraventricular or extraventricular). Most hydrocephalus is obstructive, and the term is used to contrast the hydrocephalus caused by overproduction of CSF.

Arrested hydrocephalus is defined as stabilization of known ventricular enlargement, probably secondary to compensatory mechanisms. These patients may decompensate, especially following minor head injuries.

Pathophysiology
Normal CSF production is 0.20-0.35 mL/min; a majority is produced by the choroid plexus, which is located within the ventricular system, mainly the lateral and fourth ventricles. The capacity of the lateral and third ventricles in a healthy person is 20 mL. Total volume of CSF in an adult is 120 mL.

Normal route of CSF from production to clearance is the following: From the choroid plexus, the CSF flows to the lateral ventricle, then to the interventricular foramen of Monro, the third ventricle, the cerebral aqueduct of Sylvius, the fourth ventricle, the 2 lateral foramina of Luschka and 1 medial foramen of Magendie, the subarachnoid space, the arachnoid granulations, the dural sinus, and finally into the venous drainage.

ICP rises if production of CSF exceeds absorption. This occurs if CSF is overproduced, resistance to CSF flow is increased, or venous sinus pressure is increased. CSF production falls as ICP rises. Compensation may occur through transventricular absorption of CSF and also by absorption along nerve root sleeves. Temporal and frontal horns dilate first, often asymmetrically. This may result in elevation of the corpus callosum, stretching or perforation of the septum pellucidum, thinning of the cerebral mantle, or enlargement of the third ventricle downward into the pituitary fossa (which may cause pituitary dysfunction).

The mechanism of NPH has not been elucidated completely. Current theories include increased resistance to flow of CSF within the ventricular system or subarachnoid villi; intermittently elevated CSF pressure, usually at night; and ventricular enlargement caused by an initial rise in CSF pressure; the enlargement is maintained despite normal pressure because of the Laplace law. Although pressure is normal, the enlarged ventricular area reflects increased force on the ventricular wall.

Frequency
United States
Incidence of congenital hydrocephalus is 3 per 1,000 live births, while the incidence of acquired hydrocephalus is not known exactly.

International
Incidence of acquired hydrocephalus is unknown. About 100,000 shunts are implanted each year in the developed countries, but little information is available for other countries.

Mortality/Morbidity
In untreated hydrocephalus, death may occur by tonsillar herniation secondary to raised ICP with compression of the brain stem and subsequent respiratory arrest.

Shunt dependence occurs in 75% of all cases of treated hydrocephalus and in 50% of children with communicating hydrocephalus.
Patients are hospitalized for scheduled shunt revisions or for treatment of shunt complications or shunt failure.
Poor development of cognitive function in infants and children, or loss of cognitive function in adults, can complicate untreated hydrocephalus. It may persist after treatment.
Visual loss can complicate untreated hydrocephalus and may persist after treatment.

Sex
Generally, incidence is equal in males and females. The exception is Bickers-Adams syndrome, an X-linked hydrocephalus transmitted by females and manifested in males. NPH has a slight male preponderance.

Age
Incidence of human hydrocephalus presents a bimodal age curve. One peak occurs in infancy and is related to the various forms of congenital malformations. Another peak occurs in adulthood, mostly resulting from NPH. Adult hydrocephalus represents approximately 40% of total cases of hydrocephalus.

read Here

Friday, 27 June 2008

Treadmill and Pharmacologic Stress Testing

Cardiovascular exercise stress testing in conjunction with an ECG has been established as one of the focal points in the diagnosis and prognosis of cardiovascular disease, specifically coronary artery disease (CAD).

Feil and Seigel first noticed the significance of cardiovascular exercise stress testing in 1928; they reported ST and T changes following exercise in 3 patients with chronic stable angina.1 The following year, Master and Oppenheimer introduced a standardized exercise protocol to assess functional capacity and hemodynamic response.

Continued research into causal mechanisms of ST displacement, refinement of exercise protocols, and determination of diagnostic and prognostic exercise variables in clinical patient subsets have continued to evolve since 1929.

After the establishment of coronary angiography as a diagnostic tool, the limitation of exercise-induced ST-segment depression as a diagnostic marker for obstructive CAD in patient populations with a low disease prevalence became apparent.

Introduction

Exercise testing is a cardiovascular stress test using treadmill bicycle exercise with ECG and blood pressure monitoring. Pharmacologic stress testing, established after exercise testing, is a diagnostic procedure in which cardiovascular stress induced by pharmacologic agents is demonstrated in patients with decreased functional capacity or in patients who cannot exercise. Pharmacologic stress testing is used in combination with imaging modalities such as radionuclide imaging and echocardiography.

Exercise stress testing, which is now widely available at a relatively low cost, is currently used most frequently to estimate prognosis and determine functional capacity, to assess the probability and extent of coronary disease, and to assess the effects of therapy. Ancillary techniques, such as metabolic gas analysis, radionuclide imaging, and echocardiography, can provide further information that may be needed in selected patients, such as those with moderate or prior risk.

Exercise physiology

The initiation of dynamic exercise results in increases in the ventricular heart rate, stroke volume, and cardiac output due to vagal withdrawal and sympathetic stimulation. Also, alveolar ventilation and venous return increase as a result of sympathetic vasoconstriction. The overall hemodynamic response depends on the amount of muscle mass involved, exercise efficiency, conditioning, and exercise intensity.

In the initial phases of exercise in the upright position, cardiac output is increased by an augmentation in stroke volume mediated through the use of the Frank-Starling mechanism and heart rate. The increase in cardiac output in the later phases of exercise is due primarily to an increase in ventricular rate.

During strenuous exertion, sympathetic discharge is maximal and parasympathetic stimulation is withdrawn, resulting in autoregulation with generalized vasoconstriction, except in the vital organs (cerebral and coronary circulations).

Venous and arterial norepinephrine release from sympathetic postganglionic nerve endings is increased, and epinephrine levels are increased at peak exertion, resulting in an increase in ventricular contractility. As exercise progresses, skeletal muscle blood flow increases; oxygen extraction increases as much as 3-fold; peripheral resistance decreases; and systolic blood pressure (SBP), mean arterial pressure, and pulse pressure usually increase. Diastolic blood pressure (DBP) remains unchanged or may increase or decrease by approximately 10 mm Hg. The pulmonary vascular bed can accommodate as much as a 6-fold increase in cardiac output, with only modest increases in pulmonary arterial pressure, pulmonary capillary wedge pressure, and right atrial pressure; this is not a limiting determinant of peak exercise capacity in healthy subjects.

The maximum heart rate and cardiac output are decreased in older individuals, related in part to decreased beta-adrenergic responsiveness. Maximum heart rate can be calculated by subtracting the patient's age (y) from 220 (has a standard deviation of 10-12 beats per minute [bpm]). The age-predicted maximum heart rate is a useful measurement for safety reasons and as an estimate of the adequacy of the stress to evoke inducible ischemia. A patient who reaches 80% of the age-predicted maximum is considered to have a good test result, and an age-predicted maximum of 90% or better is considered excellent.

In the postexercise phase, hemodynamics return to baseline within minutes of discontinuing exercise. The return of vagal stimulation is an important cardiac deceleration mechanism after exercise and is more pronounced in well-trained athletes but blunted in patients with chronic congestive heart failure. Intense physical work or important cardiorespiratory impairment may interfere with achievement of a steady state, and an oxygen deficit occurs during exercise. The oxygen debt is the total oxygen uptake in excess of the resting oxygen uptake during the recovery period.

Thursday, 26 June 2008

Cor pulmonale

Cor pulmonale is defined as an alteration in the structure and function of the right ventricle caused by a primary disorder of the respiratory system. Pulmonary hypertension is the common link between lung dysfunction and the heart in cor pulmonale. Right-sided ventricular disease caused by a primary abnormality of the left side of the heart or congenital heart disease is not considered cor pulmonale, but cor pulmonale can develop secondary to a wide variety of cardiopulmonary disease processes. Although cor pulmonale commonly has a chronic and slowly progressive course, acute onset or worsening cor pulmonale with life-threatening complications can occur.
Pathophysiology: Several different pathophysiologic mechanisms can lead to pulmonary hypertension and, subsequently, to cor pulmonale. These pathogenetic mechanisms include (1) pulmonary vasoconstriction due to alveolar hypoxia or blood acidemia; (2) anatomic compromise of the pulmonary vascular bed secondary to lung disorders, eg, emphysema, pulmonary thromboembolism, interstitial lung disease; (3) increased blood viscosity secondary to blood disorders, eg, polycythemia vera, sickle cell disease, macroglobulinemia; and (4) idiopathic primary pulmonary hypertension. The result is increased pulmonary arterial pressure.
The right ventricle (RV) is a thin-walled chamber that is more a volume pump than a pressure pump. It adapts better to changing preloads than afterloads. With an increase in afterload, the RV increases systolic pressure to keep the gradient. At a point, further increase in the degree of pulmonary arterial pressure brings significant RV dilation, an increase in RV end-diastolic pressure, and circulatory collapse. A decrease in RV output with a decrease in diastolic left ventricle (LV) volume results in decreased LV output. Since the right coronary artery, which supplies the RV free wall, originates from the aorta, decreased LV output diminishes blood pressure in the aorta and decreases right coronary blood flow. This is a vicious cycle between decreases in LV and RV output.
Right ventricular overload is associated with septal displacement toward the left ventricle. Septal displacement, which is seen in echocardiography, can be another factor that decreases LV volume and output in the setting of cor pulmonale and right ventricular enlargement. Several pulmonary diseases cause cor pulmonale, which may involve interstitial and alveolar tissues with a secondary effect on pulmonary vasculature or may primarily involve pulmonary vasculature. Chronic obstructive pulmonary disease (COPD) is the most common cause of cor pulmonale in the United States.
Cor pulmonale usually presents chronically, but 2 main conditions can cause acute cor pulmonale: massive pulmonary embolism (more common) and acute respiratory distress syndrome (ARDS). The underlying pathophysiology in massive pulmonary embolism causing cor pulmonale is the sudden increase in pulmonary resistance. In ARDS, 2 factors cause RV overload: the pathologic features of the syndrome itself and mechanical ventilation. Mechanical ventilation, especially higher tidal volume, requires a higher transpulmonary pressure. In chronic cor pulmonale, right ventricular hypertrophy (RVH) generally predominates. In acute cor pulmonale, right ventricular dilatation mainly occurs.
Frequency:
In the US: Cor pulmonale is estimated to account for 6-7% of all types of adult heart disease in the United States, with chronic obstructive pulmonary disease (COPD) due to chronic bronchitis or emphysema the causative factor in more than 50% of cases. Although the prevalence of COPD in the United States is about 15 million, the exact prevalence of cor pulmonale is difficult to determine because it does not occur in all cases of COPD and the physical examination and routine tests are relatively insensitive for the detection of pulmonary hypertension. In contrast, acute cor pulmonale usually is secondary to massive pulmonary embolism. Acute massive pulmonary thromboembolism is the most common cause of acute life-threatening cor pulmonale in adults. In the United States, 50,000 deaths are estimated to occur per year from pulmonary emboli and about half occur within the first hour due to acute right heart failure.
Internationally: Incidence of cor pulmonale varies among different countries depending on the prevalence of cigarette smoking, air pollution, and other risk factors for various lung diseases.
Mortality/Morbidity: Development of cor pulmonale as a result of a primary pulmonary disease usually heralds a poorer prognosis. For example, patients with COPD who develop cor pulmonale have a 30% chance of surviving 5 years. However, whether cor pulmonale carries an independent prognostic value or it is simply reflecting the severity of underlying COPD or other pulmonary disease is not clear. Prognosis in the acute setting due to massive pulmonary embolism or ARDS has not been shown to be dependent on presence or absence of cor pulmonale.

Grey Matter - from the writers of Grey's Anatomy