Cor Pulmonale

Cor pulmonale refers to right ventricular enlargement and dysfunction resulting from a primary disorder of the respiratory system, most commonly chronic hypoxic lung disease causing pulmonary vasoconstriction and, over time, structural pulmonary vascular remodeling and sustained pulmonary hypertension.

Chronic obstructive pulmonary disease is the most common underlying cause. Other causes include interstitial lung disease, chronic pulmonary embolism (chronic thromboembolic pulmonary hypertension), obstructive sleep apnea, and other causes of chronic hypoxia or pulmonary vascular obstruction.

By convention, cor pulmonale specifically excludes right heart failure arising from left heart disease or a primary cardiac cause, though the distinction can become blurred as disease progresses.

Symptoms of the underlying lung disease, most commonly progressive exertional dyspnea, are typically present and often long standing before signs of right heart involvement become apparent.

Examination findings reflect right heart strain and congestion:

• Raised jugular venous pressure.
• A parasternal heave (reflecting right ventricular hypertrophy).
• A loud pulmonary component of the second heart sound.
• Peripheral edema.
• In more advanced disease, ascites and hepatomegaly, sometimes with a pulsatile liver edge if significant tricuspid regurgitation has developed.

Cyanosis may be present, reflecting the underlying hypoxic lung disease. Signs of the specific underlying respiratory condition, such as hyperinflation and reduced breath sounds in chronic obstructive pulmonary disease, or fine crackles in interstitial lung disease, are often evident on examination.

Echocardiography is central to diagnosis. It assesses right ventricular size and function, estimates pulmonary artery pressure from tricuspid regurgitant jet velocity, and helps exclude a primary left heart cause for the right heart findings.

ECG may show right axis deviation, right ventricular hypertrophy (dominant R wave in V1), right atrial enlargement (P pulmonale, a tall, peaked P wave), and, in more severe cases, a right bundle branch block pattern.

Arterial blood gas typically shows chronic hypoxia, often with compensated hypercapnia if the underlying cause is advanced chronic obstructive pulmonary disease. Pulmonary function testing characterizes the underlying respiratory disease. CT chest assesses the underlying lung parenchyma and can identify chronic thromboembolic disease as a cause.

Right heart catheterization is the definitive investigation for confirming pulmonary hypertension and quantifying its severity. Given the invasive nature of the test, it is generally reserved for cases where the diagnosis remains uncertain after non-invasive assessment, or where specific pulmonary hypertension targeted therapy is being considered.

Differentials include:

• Right heart failure secondary to left heart disease (see Heart Failure entry), a much more common overall cause of right heart congestion than primary cor pulmonale.
• Primary pulmonary arterial hypertension, a distinct condition not secondary to lung disease, managed with specific pulmonary vasodilator therapy under specialist care.
• Constrictive pericarditis (see Pericarditis entry), which can mimic right heart failure.

Treatment of the underlying respiratory disease is the primary focus of management, since this addresses the driving pathological process rather than the secondary cardiac consequence:

• optimized inhaled therapy and smoking cessation for chronic obstructive pulmonary disease (see that entry)
• treatment of the specific underlying cause for interstitial lung disease
• continuous positive airway pressure for obstructive sleep apnea
• anticoagulation with consideration of pulmonary endarterectomy or balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension

Long term oxygen therapy is a key intervention where chronic hypoxia is present. Correcting hypoxia reduces the hypoxic pulmonary vasoconstriction that drives the pulmonary hypertension. It has been shown to improve survival in hypoxic chronic obstructive pulmonary disease specifically (see that entry for the specific oxygen saturation and PaO2 thresholds used to guide this decision).

Diuretics are used cautiously for peripheral edema and congestive symptoms, but should be used judiciously, since the right ventricle in this setting is often preload dependent and excessive diuresis can reduce cardiac output and worsen symptoms.

Pulmonary vasodilator therapy, of the type used in primary pulmonary arterial hypertension, is generally not recommended for cor pulmonale secondary to chronic lung disease. Evidence of benefit in this specific population is lacking, and such therapy can worsen ventilation perfusion matching by dilating vessels in poorly ventilated lung regions.

Referral:

• Respiratory medicine for optimization of the underlying lung disease and assessment for long term oxygen therapy.
• Cardiology for confirmation of right heart involvement and exclusion of a primary cardiac cause.
• Specialist pulmonary hypertension service for chronic thromboembolic pulmonary hypertension or where the diagnosis remains uncertain.