What are the criteria for assessing cor pulmonale in a patient?

Cor Pulmonale Assessment Criteria

Echocardiographic Criteria (Primary Diagnostic Modality)

Echocardiography is the primary non-invasive tool for assessing cor pulmonale, having largely replaced invasive right heart catheterization for initial evaluation. 1, 2

Tricuspid Regurgitation Velocity (Most Important Parameter)

• Tricuspid regurgitation velocity >3.4 m/s (corresponding to PA systolic pressure >50 mmHg) indicates moderate to severe cor pulmonale 1
• Velocity 2.9-3.4 m/s (PA systolic pressure 37-50 mmHg) indicates mild cor pulmonale 1
• Velocity ≤2.8 m/s (PA systolic pressure ≤36 mmHg) excludes cor pulmonale 1

Right Ventricular Structural Changes

• Right ventricle/left ventricle basal diameter ratio >1.0 confirms right ventricular enlargement 1
• Flattening of interventricular septum (left ventricular eccentricity index >1.1 in systole and/or diastole) indicates right ventricular pressure overload 1
• Right atrial area (end-systole) >18 cm² indicates right atrial enlargement 1

Pulmonary Vascular Parameters

• Right ventricular outflow Doppler acceleration time <105 msec and/or midsystolic notching suggests increased pulmonary vascular resistance 1
• Early diastolic pulmonary regurgitation velocity >2.2 m/sec indicates elevated pulmonary artery pressure 1
• Pulmonary artery diameter >25 mm suggests pulmonary hypertension 1

Inferior Vena Cava Assessment

• IVC diameter >21 mm with decreased inspiratory collapse (<50% with sniff or <20% with quiet inspiration) suggests elevated right atrial pressure 1

Hemodynamic Confirmation (Gold Standard)

Right heart catheterization remains the definitive diagnostic test, with mean pulmonary artery pressure (mPAP) ≥25 mmHg confirming pulmonary hypertension. 1 However, this is reserved for cases requiring precise hemodynamic assessment, as similar prognostic information can be obtained from simpler measurements like FEV1 and blood gases. 3

Clinical Assessment

Physical Examination Findings

Physical examination has poor sensitivity for detecting moderate cor pulmonale and should never be relied upon alone. 1 Key findings include:

• Raised jugular venous pressure 1
• Right ventricular heave (parasternal lift) 1
• Loud pulmonary second heart sound (P2) 1
• Tricuspid regurgitation murmur 1
• Peripheral edema 1
• Central cyanosis 1

Arterial Blood Gas Analysis

Chronic hypoxemia (PaO₂ <60 mmHg or 8 kPa) is the primary driver of pulmonary hypertension in COPD and mandates assessment for cor pulmonale. 1 This measurement is essential if FEV₁ <50% predicted or clinical signs of respiratory failure are present. 4

Electrocardiographic Findings

ECG has poor sensitivity (46.8-62.5%) for mild to moderate pulmonary hypertension but reaches 100% sensitivity in severe cases (mPAP ≥40 mmHg). 5 Findings include:

• Right axis deviation for age 1
• Right atrial enlargement (P pulmonale) 1
• Right ventricular hypertrophy 1
• In acute cor pulmonale: S1Q3T3 pattern, S1S2S3 pattern, negative T waves in right precordial leads, transient right bundle branch block 1

Chest Radiography

Chest X-ray is frequently normal in early disease and should not be used to exclude cor pulmonale. 1 Suggestive findings include:

• Right descending pulmonary artery >16 mm indicates likely pulmonary hypertension 3, 1
• Central pulmonary artery enlargement 1
• Right heart chamber enlargement 1
• Lung hyperinflation and hyperlucent areas with peripheral vascular pruning 1

Computed Tomography Criteria

CT is not routinely recommended but can identify: 1

• Main pulmonary artery diameter ≥29 mm (sensitivity 87%, specificity 89%) 1
• Segmental pulmonary artery/bronchus ratio >1:1 1
• Right ventricular free wall thickness ≥6 mm 1
• Mosaic attenuation pattern 1

Nocturnal Assessment

Nocturnal oximetry or polysomnography is indicated when cor pulmonale or polycythemia is present despite only moderate daytime hypoxemia (PaO₂ 55-65 mmHg). 3, 1 Nocturnal desaturation contributes significantly to pulmonary hypertension development. 3

Critical Pitfalls to Avoid

• Do not rely on physical examination alone - it has poor sensitivity for moderate cor pulmonale 1
• Echocardiographic assessment may be challenging in COPD patients with hyperinflated lungs - use subcostal views for adequate visualization 1
• Do not overlook cor pulmonale in obese patients or those with multiple comorbidities where physical findings may be masked 1
• Awake oxygen saturation does not predict nocturnal hypoxemia - separate nocturnal assessment is required when clinically indicated 1