What is cor pulmonale and can it be diagnosed acutely?

Cor Pulmonale: Definition and Acute Diagnosis

Cor pulmonale is defined as right ventricular hypertrophy and/or dilation caused by pulmonary hypertension secondary to diseases affecting the structure and/or function of the lungs, and it can be diagnosed acutely through echocardiography which reveals a severely dilated hypokinetic right ventricle with interventricular septal deviation into the left ventricle. 1, 2

Definition and Classification

Cor pulmonale can be classified as:

• Acute cor pulmonale: Generally associated with massive pulmonary thromboembolism, characterized by sudden onset of right ventricular failure due to abrupt increase in pulmonary vascular resistance 1, 3
• Chronic cor pulmonale: More commonly associated with chronic respiratory diseases, particularly COPD, developing gradually over time 1, 4

The American Heart Association defines cor pulmonale as the structural and functional alteration of the right ventricle caused by secondary pulmonary hypertension due to diseases affecting the lungs, not by left cardiac or congenital disorders 1.

Pathophysiology

The main mechanisms leading to cor pulmonale include:

• Increased pulmonary vascular resistance due to chronic alveolar hypoxia causing pulmonary vascular remodeling 4
• Mechanical narrowing of vessels and obstruction of the pulmonary vascular bed 5
• In acute settings (like pulmonary embolism), sudden obstruction of pulmonary vessels leading to right ventricular pressure overload 2

Clinical Presentation

Patients with cor pulmonale typically present with:

• Progressive dyspnea
• Peripheral edema
• Elevated jugular venous pressure
• Hepatomegalia and ascites in advanced cases
• Palpable right ventricular impulse
• Accentuation of the pulmonary component of the second heart sound 1

In acute cor pulmonale, patients may present with:

• Obstructive shock
• Persistent hypotension (systolic BP <90 mmHg)
• End-organ hypoperfusion
• Cardiac arrest in severe cases 2

Acute Diagnosis of Cor Pulmonale

Cor pulmonale can be diagnosed acutely through several methods:

1. Echocardiography

• Most valuable tool for acute diagnosis - reveals severely dilated hypokinetic right ventricle with deviation of the interventricular septum into the left ventricle 2
• Non-invasive method useful for evaluating right ventricular structure and function and estimating pulmonary arterial pressure 1
• Recommended as first-line imaging for non-invasive diagnostic assessment of suspected pulmonary hypertension in patients with lung disease 2

2. Electrocardiogram

• May show right axis deviation, right ventricular hypertrophy, strain, and right bundle branch block 1
• Useful as a screening tool but less sensitive than echocardiography

3. Chest Radiography

• Can show central pulmonary arterial dilation with "pruning" of peripheral vessels
• Enlargement of the right atrium and ventricle in advanced cases 1
• If the maximum diameter of the right descending pulmonary artery exceeds 16 mm, pulmonary hypertension is likely 2

4. CT Pulmonary Angiography

• Particularly useful in cases of suspected pulmonary embolism causing acute cor pulmonale
• Can identify patterns of emphysema and other lung pathologies contributing to cor pulmonale 2

5. Right Heart Catheterization

• Gold standard for confirming pulmonary hypertension
• Defines mean pulmonary arterial pressure (mPAP >20 mmHg based on recent Nice statement) 6
• Not recommended for routine assessment unless therapeutic consequences are expected 2

Acute Management Considerations

In acute cor pulmonale, especially due to pulmonary embolism:

• Immediate hemodynamic stabilization is crucial
• Right ventricular output may be improved using inotropes such as dobutamine and milrinone 2
• Specific interventions to decrease pulmonary vascular resistance include sildenafil, inhaled or intravenous prostacyclin, and inhaled nitric oxide 2
• Hypotension should be treated with vasopressors such as norepinephrine or vasopressin 2
• Avoid excessive fluid administration as it can increase right ventricular distention and worsen cardiac output 2
• In massive pulmonary embolism causing acute cor pulmonale, thrombolytic therapy should be considered if not contraindicated 2

Important Clinical Pearls

• Physical signs of cor pulmonale can be difficult to detect in patients with COPD due to pulmonary hyperinflation masking cardiac findings 1
• Acute cor pulmonale can rapidly progress to obstructive shock and cardiac arrest if not promptly recognized and treated 2
• Hypoxia, acidosis, and hypercapnia should be avoided as they increase pulmonary vascular resistance and lead to further right heart failure 2
• Patients with severe or "disproportionate" pulmonary hypertension (PAP >40 mmHg) represent a minority (<5%) of COPD patients and may require specialized management 4

By recognizing the clinical presentation and utilizing appropriate diagnostic tools, particularly echocardiography, cor pulmonale can be diagnosed acutely, allowing for timely intervention and management.