What is cor pulmonale, a condition often associated with chronic obstructive pulmonary disease (COPD), pneumonia, or cystic fibrosis?

Definition of Cor Pulmonale

Cor pulmonale is right ventricular enlargement (hypertrophy and/or dilation) secondary to pulmonary hypertension caused by diseases affecting the structure and/or function of the lungs, excluding left heart disease or congenital heart disease. 1, 2

Core Pathophysiologic Features

The condition develops through a specific sequence of pulmonary and cardiac changes:

• Primary pulmonary disease causes increased pulmonary vascular resistance, leading to pulmonary hypertension (mean pulmonary artery pressure >20 mmHg by current definitions, though historically >25 mmHg was used) 2, 3
• Right ventricular adaptation occurs as the RV hypertrophies and dilates in response to the increased afterload from elevated pulmonary pressures 1, 4
• Progression to right heart failure may eventually develop with time as the RV decompensates under chronic pressure overload 2, 4

Primary Etiologies

COPD represents the leading cause of cor pulmonale, accounting for the vast majority of cases:

• Chronic obstructive pulmonary disease is by far the most common etiology, with two-thirds of patients with advanced COPD demonstrating pulmonary hypertension on echocardiography 5
• Interstitial lung disease (particularly idiopathic pulmonary fibrosis) represents the second most common cause 2
• Obesity-hypoventilation syndrome and other chronic hypoventilation disorders contribute to a smaller proportion of cases 2, 4
• Chronic thromboembolic disease with multiple pulmonary emboli can lead to chronic cor pulmonale, though this represents a distinct subset 4

Key Pathophysiologic Mechanisms

Three primary mechanisms drive the development of pulmonary hypertension in cor pulmonale:

• Chronic alveolar hypoxia induces pulmonary vascular remodeling through hypoxic pulmonary vasoconstriction, representing the major determinant of elevated pulmonary artery pressure 2
• Mechanical narrowing and destruction of the pulmonary vascular bed occurs from parenchymal lung disease (particularly emphysema in COPD) 4
• Vascular obstruction from thromboembolism or in situ thrombosis reduces the functional pulmonary vascular cross-sectional area 4

Severity Spectrum in COPD

The degree of pulmonary hypertension in cor pulmonale varies considerably:

• Mild to moderate elevation is typical, with resting mean pulmonary artery pressure usually ranging between 20-35 mmHg in stable COPD patients 2
• Severe or "disproportionate" pulmonary hypertension (mean PAP >40 mmHg) occurs in less than 5% of COPD patients and involves mechanisms that are not fully understood, potentially including primary pulmonary arterial remodeling similar to pulmonary arterial hypertension 5, 2, 3
• Dynamic worsening occurs during exercise, sleep, and acute exacerbations, with these acute increases in afterload potentially precipitating right heart failure 2

Clinical Context and Comorbidity

Cor pulmonale frequently coexists with other cardiovascular conditions in COPD:

• Overlap with left heart disease is common, as 20-70% of COPD patients have concomitant heart failure, and unrecognized left ventricular dysfunction may mimic acute exacerbations 5
• Cardiovascular comorbidities including ischemic heart disease, hypertension, and arrhythmias are highly prevalent and contribute to overall disease severity 5
• Overlap syndrome (COPD with obstructive sleep apnea) increases risk of developing daytime pulmonary hypertension and more severe cor pulmonale compared to either condition alone 5

Important Diagnostic Considerations

• Acute versus chronic differentiation is clinically important, as acute cor pulmonale from massive pulmonary thromboembolism presents differently from chronic forms due to COPD, though both show RV dysfunction 6
• Contributing factors beyond structural lung disease include arterial hypoxemia with resultant polycythemia, hypercapnia, and respiratory acidosis, all of which increase RV afterload 1
• Exclusion criteria require ruling out left heart disease or congenital heart disease as the primary cause of RV enlargement, as these represent different disease entities 1, 2