Definition

The term cor pulmonale or pulmonary heart disease refers to patients exhibiting pulmonary arterial hypertension (PAH) resulting in progressive right ventricular hypertrophy, dilation, and eventual cardiac decompensation. This arises from disorders that affect ventilatory drive or musculoskeletal respiratory mechanics; pulmonary airway, infiltrative, fibrotic, or vascular diseases; and diseases that are primarily cardiac but affect the pulmonary circulation and the lungs.

Incidence and prevalence

In individuals older than 50 years of age, cor pulmonale is the third most common cardiac disorder (after ischemic heart disease and hypertensive cardiac disease). The male-to-female ratio of incidence of the disease is 5:1; 10% to 30% of patients admitted to the hospital with coronary heart failure exhibit cor pulmonale.

The prognosis is determined by the pulmonary disease responsible for the increased pulmonary vascular resistance (PVR). In patients with COPD in whom Pao₂ can be maintained at near-normal levels, the prognosis is favorable. However, cor pulmonale associated with hypoxic lung disease is associated with a 70% rate of mortality within 5 years after onset of associated peripheral edema. The prognosis is poor for patients in whom cor pulmonale is the result of gradual obstruction of pulmonary vessels by intrinsic pulmonary vascular disease or pulmonary fibrosis. These anatomic changes cause irreversible alterations in the pulmonary vasculature, resulting in fixed elevations of PVR.

Pathophysiology

COPD is associated with the functional loss of pulmonary capillaries and the subsequent arterial hypoxemia; these events initiate pulmonary vasoconstriction, which is the leading cause of chronic cor pulmonale. Sustained pulmonary vasoconstriction produces hypertrophy of the smooth muscle in the tunica media and an irreversible increase in the PVR. In the presence of chronically elevated pulmonary capillary pressure, the lungs are increasingly resistant to pulmonary edema because lymph vessels expand and their ability to carry fluid away from the interstitial spaces increases. The lymphatic pumping action creates a suction effect, which results in a negative pleural pressure. The rate at which right ventricular dysfunction develops depends on the magnitude of pressure increase in the pulmonary circulation and on the rapidity with which this increase occurs. For example, PE may result in right ventricular failure in the presence of a mean PAP as low as 30 mmHg. By contrast, when PAH occurs gradually, as it does in COPD, right ventricular compensation occurs; congestive heart failure rarely occurs before mean PAP exceeds 50 mmHg.