Cor Pulmonale

Etiology

Pulmonary hypertension is associated with diseases of the lung (e.g., chronic obstructive pulmonary disease, interstitial lung disease), vasculature (e.g., idiopathic pulmonary arterial hypertension), upper airway (e.g., obstructive sleep apnea), or chest wall (e.g., kyphoscoliosis). Diseases that damage lungs are autoimmune (e.g., scleroderma), cystic fibrosis, and obesity hypoventilation syndrome are also lead to pulmonary hypertension.

Massive pulmonary embolism is the most common cause of acute cor pulmonale.

A massive pulmonary embolism can mimic a myocardial infarction with elevated troponins, ST changes, chest pain, and shortness of breath.

Chronic obstructive pulmonary disease (COPD) is the most common cause of cor pulmonale. The severity of cor pulmonale appears to correlate with the magnitude of hypoxemia, hypercapnia, and airflow obstruction.

In most patients with COPD, cor pulmonale tends to be accompanied by mild pulmonary hypertension (i.e., mean pulmonary artery pressure 40 mmHg or less).

Epidemiology

The exact prevalence of cor pulmonale is difficult to determine, as physical examination and routine tests are relatively insensitive for the detection of pulmonary hypertension and RV dysfunction. Cor pulmonale is estimated to account for 6% to 7% percent of all types of adult heart disease in the United States. The incidence of cor pulmonale is widely variant among countries. It depends on air pollution, the prevalence of cigarette smoking and other risk factors for various lung diseases.

Pathophysiology

The pathophysiology of cor pulmonale is a result of increased right-sided filling pressures from pulmonary hypertension that is associated with diseases of the lung.[5][6][7]

Under normal physiologic conditions, the right ventricle pumps against a low-resistance circuit.

Normal pulmonary vascular resistance is approximately one-tenth of the resistance of the systemic arteries. Chronic hypoxemia leading to chronic vasoconstriction produces smooth muscle proliferation in small pulmonary arteries. Hypoxemia produces changes in vascular mediators such as Nitric Oxide, Endothelin1 (ET1) and platelet-derived growth factors (PDGF A and B). Nitric oxide is a vasodilator; hypoxemia reduces endothelial cell production of nitric oxide and results in impaired smooth ms relaxation.

The initial pathophysiologic event in the production of cor pulmonale is an elevation of pulmonary vascular resistance. As the resistance increases, the pulmonary arterial pressure rises, and the right ventricular work increases leading to right ventricular enlargement (e.g., thickening, dilation, or both).

History and Physical

Symptoms may include dyspnea on exertion (most common), fatigue, lethargy, exertional syncope and exertional chest pain, abdominal edema or distension, and lower extremity edema.

The clinical signs occur late, being observed at an advanced stage of the disease far after the development of pulmonary hypertension.

Physical findings may include: 

• Jugular venous distension: Prominent jugular V wave, indicating the presence of tricuspid regurgitation
• Peripheral (ankle) edema: The best sign of RHF, but it is not specific and can arise from other causes
• Cardiovascular: Palpable left the parasternal lift, loud S2 (accentuation of the pulmonary component of the second heart sound) narrow splitting of S2, a holosystolic murmur of tricuspid regurgitation at the left lower sternal border, right-sided S4 heart sound
• Abdomen: Hepatomegaly, ascites.

Evaluation

Laboratory investigations are directed toward defining the potential underlying etiologies as well as evaluating the complications of cor pulmonale.[8][9][10] These include:

• Chest radiograph: Enlargement of the pulmonary artery may be seen, cardiomegaly is confined predominantly, if not exclusively, to the right ventricle and other features may be detected according to the cause
• Electrocardiogram: Shows features of right ventricular hypertrophy/enlargement
• Doppler echocardiography (most practical but heavily operator dependent): The non-invasive diagnosis of pulmonary hypertension is presently based on echocardiography. Continuous-wave Doppler echocardiography allows the calculation of the trans tricuspid pressure gradient from the peak velocity of the tricuspid regurgitant jet
• Chest CT angiography to rule out pulmonary thromboembolism as a cause. Main pulmonary artery diameter measurements greater than 29 mm have a sensitivity of 84% and specificity of 75% for the diagnosis of pulmonary hypertension
• Ventilation/perfusion (V/Q) scanning can be particularly useful in evaluating patients with cor pulmonale, especially if pulmonary hypertension is due to chronic thromboembolic pulmonary hypertension (CTEPH)
• MRI: This noninvasive technique yields highly accurate dimensions of the right ventricle but is not routinely used
• PFTs and 6-minute walk test for assessment of the severity of lung disease and exercise capacity respectively
• A right heart cath is a gold standard for diagnosis, assessment of Pulmonary hypertension severity. Right heart catheterization reveals evidence of right ventricular (RV) dysfunction (mean pulmonary artery pressure (PAP) above 25 mmHg) without left ventricular (LV) dysfunction. Differentiating left-sided from the right-sided disease includes measuring the pulmonary capillary wedge pressure (PCWP), which is an estimation of left atrial pressure. Thus, RV dysfunction is also defined as having a PCWP below 15 mmHg.

Treatment / Management

Treatment is aimed primarily at treating the underlying condition; the aim is improving oxygenation and right ventricular (RV) function by increasing RV contractility and decreasing pulmonary vasoconstriction.

Oxygen therapy relieves hypoxemic pulmonary vasoconstriction, which then improves cardiac output, lessens sympathetic vasoconstriction, alleviates tissue hypoxemia, and improves renal perfusion.

Diuretics are used to decrease the elevated right ventricular (RV) filling volume in patients with chronic cor pulmonale.

The use of cardiac glycosides, such as digitalis in patients with cor pulmonale has been controversial, and the beneficial effect of these drugs is not as obvious as in the setting of left heart failure. Nevertheless, studies have confirmed a modest effect of digitalis on the failing right ventricle in patients with chronic cor pulmonale.

Differential Diagnosis

• Atrial myxoma

• Blood disorders that are associated with increased blood viscosity

• Chronic thromboembolic pulmonary hypertension

• Congestive (biventricular) heart failure

• Constrictive pericarditis

• High-output heart failure

• Infiltrative cardiomyopathies

• Interstitial lung disease (ILD)

• Obstructive sleep apnea (OSA)

• Primary pulmonic stenosis

• Pulmonary hypertension

• Right heart failure due to congenital heart diseases

• Right heart failure due to right ventricular infarction

• Ventricular septal defect

Prognosis

Prognosis: 

The prognosis of cor pulmonale is variable-dependant upon the underlying pathology. The development of cor pulmonale as a result of a primary pulmonary disease usually heralds a poorer prognosis.

Highlights:

• Cor pulmonale is right ventricular dysfunction from long-standing pulmonary HTN.
• All primary lung diseases can cause PHTN and thus cor pulmonale.
• Dyspnea on exertion is the most common symptom.
• Primarily, treatment aims to treat the underlying condition.