What is cor pulmonale?

What is Cor Pulmonale

Cor pulmonale is right ventricular enlargement, hypertrophy, and/or dysfunction resulting from pulmonary hypertension caused by diseases affecting the structure or function of the lungs or pulmonary vasculature, explicitly excluding left heart disease as a cause. 1

Pathophysiologic Mechanism

The condition develops when the right ventricle faces chronically increased afterload from pulmonary hypertension, leading to progressive right ventricular adaptation that eventually results in dilation and failure. 1 This pulmonary hypertension is "pre-capillary" in nature, caused by increased pulmonary vascular resistance rather than left-sided cardiac pathology. 2

Two primary vascular mechanisms drive the sustained elevation in pulmonary arterial pressure:

• Persistent vasoconstriction triggered by chronic alveolar hypoxia, hypercarbia, or acidosis 3, 4
• Vascular structural remodeling including medial hypertrophy, abnormal extension of muscle to peripheral arteries, endothelial cell injury, intimal proliferation, and adventitial thickening 3

The combination of these processes causes vascular luminal narrowing and vessel obliteration that reduces pulmonary vascular surface area to the critical degree necessary for pulmonary hypertension development. 4 A critical pathophysiologic consequence is ventricular interdependence, where right ventricular dilation causes leftward septal shift, compressing the left ventricular cavity and impairing left ventricular filling, which ultimately reduces cardiac output. 1

Clinical Classification

Acute cor pulmonale develops from sudden increases in right ventricular afterload or decreased right ventricular contractility, characterized by severely dilated hypokinetic right ventricle with septal deviation into the left ventricle. 1 The most common cause is massive pulmonary embolism. 1

Chronic cor pulmonale most commonly results from chronic obstructive pulmonary disease (COPD), followed by idiopathic pulmonary fibrosis and obesity-hypoventilation syndrome. 1, 2 In COPD specifically, pulmonary hypertension is typically mild to moderate, with resting pulmonary artery mean pressure usually ranging between 20 and 35 mmHg in stable disease. 2 However, a minority (<5%) of COPD patients exhibit severe or "disproportionate" pulmonary hypertension (mean pulmonary artery pressure >40 mmHg), the mechanism of which remains poorly understood. 2

Underlying Etiologies

Cor pulmonale results from three main pathophysiologic categories: 1

• Lung parenchymal diseases (COPD, interstitial lung disease, cystic fibrosis)
• Ventilatory disorders (obesity-hypoventilation syndrome, neuromuscular disease, chest wall deformities)
• Pulmonary vascular diseases (chronic thromboembolic disease, primary pulmonary hypertension, pulmonary vasculitis)

Structural Changes in Chronic Lung Disease

In patients with chronic lung disease of infancy (which provides insight into structural mechanisms applicable to adult disease), both functional and structural lung changes produce pulmonary hypertension. 3 Alveolar development is impaired with reduced alveolar numbers, and because arteries accompany airways, there is a reduced number of intraacinar arteries. 3 The arteries that are present frequently undergo remodeling with medial hypertrophy and abnormal extension of muscle to peripheral arteries (those accompanying alveolar ducts and alveoli), plus endothelial cell injury and intimal proliferation. 3 Arteries coursing through scarred regions have further reduction in external diameter. 3 Structural remodeling shows a trend toward decreased medial hypertrophy with age, representing an attempt at normal adaptation. 3

Prognostic Implications

Declining pulmonary artery pressure in the setting of persistently high pulmonary vascular resistance is an ominous finding indicating decompensated right ventricular failure with reduced cardiac output. 1 Supraventricular arrhythmias occur in 25% of patients after 5 years and almost invariably lead to clinical deterioration. 1

Diagnostic Approach

Physical examination should focus on detecting: 1

• Left parasternal lift (right ventricular heave)
• Accentuated pulmonary component of S2
• Right ventricular S3 gallop
• Pansystolic murmur of tricuspid regurgitation
• Elevated jugular venous pressure
• Hepatomegaly, ascites, peripheral edema
• Cool extremities

Echocardiography is the primary diagnostic modality for identifying and characterizing cor pulmonale. 1 Diagnostic criteria include: 1, 5

• Right ventricular/left ventricular basal diameter ratio >1.0
• Left ventricular eccentricity index >1.1 (indicating septal flattening)
• Tricuspid regurgitation velocity >3.4 m/s
• Right ventricular outflow Doppler acceleration time <105 msec
• Early diastolic pulmonary regurgitation velocity >2.2 m/sec

Right heart catheterization remains the gold standard for confirming pulmonary hypertension with mean pulmonary artery pressure ≥25 mmHg. 1, 5

Common Diagnostic Pitfalls

Echocardiographic assessment may be challenging in patients with hyperinflated lungs due to COPD, but subcostal views can usually provide adequate visualization. 5 Physical examination has poor sensitivity for detecting moderate cor pulmonale, particularly in patients with obesity or other comorbidities. 5 Chest radiography is frequently normal in early disease and should not be used to exclude cor pulmonale. 5