Perhaps the most widely accepted general definition of the term cor pulmonale remains the one articulated in 1963 by an expert committee appointed by the director general of the World Health Organization (WHO): Chronic cor pulmonale is "hypertrophy of the right ventricle resulting from diseases affecting the function and/or structure of the lung, except when these pulmonary alterations are the result of diseases that primarily affect the left side of the heart or congenital heart disease."1 In the updated clinical classification of pulmonary hypertension, cor pulmonale can occur due to conditions included in the third (pulmonary hypertension due to lung diseases and/or hypoxia) and fourth categories (pulmonary hypertension due to chronic thrombotic and/or embolic disease).2 Of note, acute dilatation of the right ventricle of the heart, that is, acute cor pulmonale, is a disorder in which the right ventricle is dilated and the muscular wall is stretched thin. This is most often the result of massive pulmonary embolism. The chronic form of the disorder, the principal subject of this chapter, is characterized by right ventricular (RV) hypertrophy with eventual dilatation and right-sided heart failure.
The right ventricle is ill suited to excessive mechanical demands, being adapted to pump blood through the normally low-resistance, high-capacitance lung circulatory bed. The final common pathophysiologic event that causes chronic cor pulmonale is chronically increased resistance to blood flow through the pulmonary circulation leading to pulmonary arterial hypertension (PAH). Unlike systemic hypertension, PAH is difficult to diagnose clinically, so pulmonary vascular pressures may be elevated for prolonged periods before the disorder is recognized. In fact, dysfunction of the right ventricle (ie, cor pulmonale) is often recognized as the initial clinical diagnosis in patients with either primary or secondary PAH. Newer noninvasive techniques can provide more information about pulmonary circulatory function than in the past. However, suspecting PAH early in its course still depends largely on the skill of the experienced clinician.
Although lung disorders that cause chronic cor pulmonale can be classified in many ways, this chapter uses a classification that is based on the mechanism by which the disorder increases pulmonary vascular resistance.
Estimates of the incidence of chronic cor pulmonale, as well as estimates of morbidity and even mortality directly attributable to right-heart dysfunction secondary to lung disease, are difficult to obtain. It is difficult to separate epidemiologic data relevant to cor pulmonale from the lung disease that is its primary cause. In addition, a definitive diagnosis most often requires invasive diagnostic procedures, often at a time when treating the lung disease is the most paramount clinical issue. However, the magnitude of the clinical problem can be appreciated from data on chronic obstructive pulmonary disease (COPD), undoubtedly the most common cause of cor pulmonale.
An estimated 24 million US adults have COPD, and it is the third leading cause of death.3,4 In the United States, >125,000 deaths are attributable to COPD every year. The ...