1 What is cor pulmonale?

The term cor pulmonale was coined by Paul Dudley White in 1931 to indicate heart failure coexistent with a primary pathologic condition of the lung. Subsequent definitions have described pathologic aspects of the right ventricle, such as hypertrophy and dilatation. Recent literature has focused on pathophysiology, diagnosis, and therapy of the continuum of pulmonary hypertension and right ventricular failure. Currently, we can define cor pulmonale as acute or chronic pressure overload of the right ventricle in response to pulmonary artery (PA) hypertension of various causes.

2 What are the subtypes of cor pulmonale?

Cor pulmonale can be acute or chronic.

3 What is the pathophysiology of right ventricular failure?

Under normal conditions, the pulmonary circulation is a low-resistance circuit, and the right ventricle generates the same stroke volume as the left ventricle with end-systolic pressures that are just 20% to 25% of those in the left ventricle. The low pressure within the thin free wall of the right ventricle also allows myocardial perfusion to occur both in systole and in diastole. Because of its structure, similar to that of veins rather than arteries, the right ventricle accommodates well additional volume but not higher pressure. When pressure overload occurs acutely, the right ventricle can only dilate and, if the pressure is sufficiently elevated, fail. Chronically, in response to increased systolic workload the free wall of the right ventricle hypertrophies and becomes similar to the left ventricle. Laplace’s law helps explaining the evolution from hypertrophy to dilatation and failure (Fig. 23-1): In a thin-wall chamber, an increase in intraluminal pressure increases wall stress unless thickness increases or the internal radius decreases. As the right ventricle hypertrophies, myocardial perfusion becomes limited to diastole, making its myocardium more susceptible to ischemia, and thus leading to dilatation and failure.

Figure 23-1 Diagrammatic cross-section of the right (RV) and left ventricular (LV) cavities. Left, Normal state. The right ventricle has a thin free wall and a characteristic crescentlike shape. Right, Right ventricular hypertrophy from pressure overload. The right ventricle assumes a spherical shape, thickened free wall, and an overall greater area than the left ventricle, which is normally the larger of the two ventricles.

(From Voelkel NF, Quaife RA, Leinwand LA, et al. Right ventricular function and failure. Report of a National Heart, Lung, and Blood Institute working group on cellular and molecular mechanisms of right heart failure. Circulation 114:1883-1891, 2006. Copyright 2006 American Heart Association.)

4 What are the causes of cor pulmonale?

Any process that results in pulmonary hypertension can cause cor pulmonale. Pulmonary hypertension is defined as mean PA pressures > 20 mm Hg at rest or > 30 mm Hg with exercise. The most frequent cause of pulmonary hypertension and cor pulmonale is COPD, due to chronic hypoxemia. In COPD the degree of hypertension is generally moderate, and oxygen supplementation may be effective in relieving some of the pressure load to the right ventricle and delaying failure. Additional causes of cor pulmonale include chronic pulmonary thromboembolic disease, left-sided cardiac abnormalities, untreated obstructive sleep apnea (OSA), interstitial lung diseases, and primary pulmonary hypertension. A comprehensive classification of the diseases of the lung associated with PA hypertension and cor pulmonale is shown in Table 23-1.

^{Table 23-1} Classification of cor pulmonale according to causative factor

5 What is the pathophysiology of PA hypertension?

Hypoxemia and vascular occlusion are the major causes of pulmonary hypertension; both result in an increase in pulmonary vascular resistance and reduction of pulmonary blood flow. Hypoxemia causes local vasoconstriction (hypoxic pulmonary vasoconstriction), which in part corrects ventilation-perfusion match and improves gas exchange. However, chronic vasoconstriction also produces smooth muscle proliferation in the small arteries, leading to increased resistance and increased PA pressure. These architectural changes may promote platelet aggregation leading to thrombus formation that further increases pulmonary artery pressure and pulmonary vascular resistance.

6 Discuss the epidemiology of cor pulmonale, with particular reference to COPD

Cor pulmonale may account for approximately 10% of all admissions for congestive heart failure. COPD is the most frequent cause of cor pulmonale, but the actual incidence is unknown. Pulmonary hypertension in COPD has been reported to occur in 30% to 70% of the cases, a wide range that underlines the lack of large epidemiologic studies of patients with mild to moderate COPD. Severe pulmonary hypertension (mean pressure over 40 mm Hg) is uncommon and does not seem to be closely related to the degree of airflow limitation. Hence, when severe pulmonary hypertension is found in patients with COPD, further causes should be sought, such as chronic embolism, left-sided heart disease, and primary pulmonary hypertension. Regardless, the presence of pulmonary hypertension in COPD is associated with a reduced lifespan.

7 What are the signs and symptoms of cor pulmonale?

Signs and symptoms of cor pulmonale develop slowly over time, as the right ventricle compensates for the increased pressure load, and become more evident as failure sets in.

Symptoms of cor pulmonale include the following:

Signs of cor pulmonale include the following:

8 What is the mortality associated with cor pulmonale?

Patients with COPD have a 62% 5-year survival rate, whereas patients with COPD and mean PA pressures in excess of 25 mm Hg have a 5-year survival of only 36% and of 30% if peripheral edema is present. It is unclear whether PA hypertension is the cause of death or whether it is a marker of increased mortality.

9 What are the electrocardiographic (ECG) findings associated with right ventricular hypertrophy?

ECG criteria for right ventricular hypertrophy are neither highly specific nor highly sensitive, and in current practice the diagnosis is better made by echocardiography. However, recognizing ECG abnormalities that may be associated with right ventricular hypertrophy remains an important diagnostic tool in the preoperative anesthetic evaluation. ECG findings commonly associated with right ventricular hypertrophy include the following: