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.