Cor Pulmonale
Allen P. Burke, M.D.
Adina Paulk, M.D.
Definition
Cor pulmonale, or pulmonary heart disease, is right ventricular enlargement with or without right heart failure resulting from pulmonary hypertension caused by structural or functional abnormalities of the pulmonary circulation.1 “Cor pulmonale” may be used for right heart enlargement from all causes of pulmonary hypertension except left-sided heart disease.2,3 Despite a lack of a clear consensus definition and a recent trend to abandon the use of the term altogether, Roberts et al. recently proposed a unifying definition. In a clinical and pathologic review, they define cor pulmonale as “dilatation of the right ventricular cavity without hypertrophy of its wall (acute and subacute cor pulmonale) or both dilatation of the right ventricular cavity and hypertrophy of its wall (chronic cor pulmonale), secondary to pulmonary hypertension not caused by a condition involving the left side of the heart.2
Pathophysiology
The pathophysiology of cor pulmonale is analogous to left-sided hypertrophy and failure brought on by increased afterload caused by systemic hypertension (see Chapter 143). The main responses to circulatory and pressure overload are right ventricular dilatation and hypertrophy, respectively. When the onset of pulmonary hypertension is sudden, dilatation occurs. When it is gradual, there is right ventricular hypertrophy and dilatation, which progress concomitantly, with eventual right-sided failure.1 A phase of right ventricular hypertrophy without dilatation, as is seen in the left ventricle, is not generally described.
Right ventricular hypertrophy is caused by chronic increased pulmonary vascular resistance, due to any of the causes of pulmonary hypertension (Table 144.1).
The general causes of cor pulmonale fall into three groups. Those characterized by a limitation to airflow (COPD and other causes of chronic bronchial obstruction) account for 80% of cases. Those characterized by a restriction of pulmonary volumes (restrictive lung diseases) account for the majority of the remainder and include idiopathic pulmonary fibrosis and pulmonary sarcoidosis. Idiopathic pulmonary arterial hypertension and associated pulmonary arterial hypertension are additional causes of cor pulmonale. Finally, there are those conditions where mechanical properties of the lungs and chest wall are preserved, but poor ventilatory drive causes gas exchange abnormalities, as in, for example, obesity-hypoventilation syndrome (formerly “pickwickian syndrome”), and obstructive sleep apnea.
Alveolar hypoxia is an important cause of pulmonary hypertension, chronic obstructive lung disease, kyphoscoliosis, and hypoventilation.
In diffuse interstitial lung disease, destruction of vessels with intimal remodeling is a contributory factor.
In diffuse interstitial lung disease, destruction of vessels with intimal remodeling is a contributory factor.
TABLE 144.1 Causes of Cor Pulmonale | ||||||||||||||||||||||||||||||||
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Acute and Subacute Cor Pulmonale
In the clinical setting, acute cor pulmonale is mainly observed as a complication of massive pulmonary embolism or acute respiratory distress syndrome.
The diagnosis is generally made by echocardiography. When evaluated along the long axis, the area of the right ventricle is enlarged compared to the left at a ratio of 0.6 and 1 (moderate cor pulmonale) or >1 (severe cor pulmonale).4 Pulmonary arterial wedge pressures are generally normal, indicating a lack of left ventricular dilatation.
In acute respiratory distress syndrome, the rate of cor pulmonale ranges from 14% to 50%.5 The main cause of pulmonary artery vasoconstriction in mechanically ventilated ARDS patients is hypercapnia, with mechanical ventilation contributing by way of an alveolar distension compressing the capillary bed in undamaged areas of the lung.4 There are various clinical strategies involving ventilator settings that have been developed to lessen the incidence of acute cor pulmonale in acute respiratory distress syndrome (“what is good for the lung is good for the right ventricle”).5
In approximately 60% of patients with massive pulmonary embolism, acute cor pulmonale is seen. Hyperacute cor pulmonale caused by massive pulmonary emboli results in cardiac dilatation without hypertrophy. Similarly, subacute cor pulmonale, often caused by embolic malignancy,2,6,7,8,9 also causes right ventricular dilatation without hypertrophy2 (Fig. 144.2).
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