What is cor pulmonale?

Cor Pulmonale: Definition and Clinical Significance

Cor pulmonale is right ventricular enlargement and/or dysfunction resulting from pulmonary hypertension caused by diseases affecting the structure and/or function of the lungs. 1

Pathophysiology

Cor pulmonale develops through the following mechanism:

1. Primary pulmonary disease → Pulmonary hypertension → Right ventricular enlargement → Right heart failure

The pathophysiological sequence involves:

• Increased pulmonary vascular resistance due to:
  • Chronic alveolar hypoxia (primary mechanism)
  • Pulmonary vascular remodeling
  • Loss of pulmonary vascular bed
  • Hypercapnia and respiratory acidosis

Etiology

Primary Causes

• Chronic Obstructive Pulmonary Disease (COPD) - the most common cause 1
• Idiopathic pulmonary fibrosis
• Obesity-hypoventilation syndrome 1
• Interstitial lung diseases
• Chronic thromboembolic disease
• Primary pulmonary hypertension 2

Classification by Mechanism

1. Asphyxial/Hypoxic type - exemplified by COPD
2. Vascular obliterative type - exemplified by chronic pulmonary thromboembolic disease 3

Clinical Presentation

Physical Examination Findings

• Peripheral edema
• Raised jugular venous pressure
• Hepatic enlargement
• Signs of pulmonary hypertension 4

Advanced Disease Signs

• Central cyanosis (with significant hypoxemia)
• Right ventricular heave
• Loud pulmonary second sound
• Tricuspid regurgitation 4

Diagnostic Features

Severity Classification

• Mild to moderate pulmonary hypertension: Pulmonary artery mean pressure (PAP) between 20-35 mmHg (most common in COPD)
• Severe/disproportionate pulmonary hypertension: PAP >40 mmHg (occurs in <5% of COPD patients) 1

Diagnostic Tests

• Electrocardiography: May show right ventricular hypertrophy
• Chest radiography: May show enlarged pulmonary arteries and right heart enlargement
• Echocardiography: Non-invasive assessment of right ventricular size and function
• Right heart catheterization: Definitive diagnosis of pulmonary hypertension 2, 3

Management

Treatment primarily targets the underlying pulmonary disease rather than the right ventricular failure itself 2:

1. Long-term oxygen therapy (LTOT): Essential treatment as hypoxia is the major determinant of elevated pulmonary artery pressure

   • LTOT can stabilize, attenuate, or sometimes partially reverse pulmonary hypertension progression 1

2. Treatment of underlying pulmonary condition:

   • Bronchodilators for COPD
   • Corticosteroids when indicated
   • Treatment of pulmonary infections
   • Smoking cessation 2, 3

3. Management of right heart failure:

   • Diuretics for peripheral edema
   • Cautious use of digoxin (controversial)
   • Phlebotomy in cases of severe polycythemia 3

4. Experimental approaches (for severe pulmonary hypertension):

   • Vasodilators
   • Endothelin receptor antagonists
   • Phosphodiesterase inhibitors (e.g., sildenafil)
   • Note: Controlled studies for these approaches in cor pulmonale are currently lacking 1, 5

Important Considerations

• Standard treatments for left ventricular heart failure may have adverse effects in patients with cor pulmonale 6
• Early detection is challenging as symptoms and signs are often nonspecific in early stages 2
• The recent redefinition of pulmonary hypertension (mPAP >20 mmHg instead of >25 mmHg) may lead to earlier detection of cor pulmonale 5

Prognosis

Prognosis depends on the severity of the underlying pulmonary disease, degree of pulmonary hypertension, and response to therapy. Early intervention before the development of right heart failure offers the best outcomes.