Right Ventricular Hypertrophy Criteria in Cor Pulmonale
Electrocardiographic diagnosis of RVH in cor pulmonale has notably poor sensitivity (27-31%) despite reasonable specificity (85-88%), making ECG an inadequate standalone diagnostic tool for this condition. 1, 2
Primary Diagnostic Approach
Echocardiography: The Superior Method
Echocardiography should be the primary diagnostic modality for detecting RVH in cor pulmonale, as it demonstrates 93% sensitivity and 95% specificity compared to ECG's 27-31% sensitivity. 2
Key echocardiographic criteria for RVH diagnosis:
- Right ventricular wall thickness (RVWT) ≥5 mm is the primary diagnostic criterion 2
- Right ventricular internal diameter index (RVIDd) >1.33 cm indicates RV dilatation 3
- Ratio of interventricular septum thickness to anterior RV wall thickness <1.99 suggests RVH 3
- Right ventricular hypertrophy, increased RV size compared to left ventricle, and abnormal interventricular septal motion 1
ECG Criteria: Limited but Specific
When ECG does show RVH, the Butler-Leggett criteria achieve 89% sensitivity in cor pulmonale (higher than the 60% in mitral stenosis), though overall ECG sensitivity remains poor. 4
Classic ECG findings in cor pulmonale include:
- Right axis deviation with deep S waves in precordial leads (characteristic of chronic obstructive lung disease) 1
- Tall R waves in right precordial leads (V1) as part of Rs, R, or Qr complexes 1
- R-wave amplitude criteria from leads I, V1, V6 and R-wave peak time in V1 1
- P-wave amplitude in lead II ≥0.25 mV (right atrial enlargement) - carries prognostic significance with 2.8-fold increased mortality risk 1
Critical Diagnostic Pitfalls
The lowest accuracy for ECG diagnosis of RVH occurs specifically in chronic lung disease, making cor pulmonale the most challenging context for electrocardiographic detection. 1
Important confounding factors:
- Hyperinflation from COPD causes low diaphragm position, creating characteristic ECG patterns that reflect anatomic changes rather than true RVH 1
- Conduction defects and old myocardial infarction mask or mimic RVH patterns on ECG, affecting 73 of 212 patients in one series 2
- Considerable RVH is required to overcome the dominant left ventricular vector, delaying ECG detection 1
Confirmatory Hemodynamic Assessment
Right heart catheterization remains the gold standard for confirming pulmonary hypertension underlying cor pulmonale, documenting mean pulmonary artery pressure ≥25 mmHg (recently revised to ≥20 mmHg), pulmonary capillary wedge pressure ≤15 mmHg, and pulmonary vascular resistance >3 Wood units. 1, 5
Practical Diagnostic Algorithm
- Obtain echocardiography first - measure RVWT (diagnostic if ≥5 mm), RVIDd, and septal thickness ratio 3, 2
- Perform ECG - apply Butler-Leggett criteria if interpretable; note that negative ECG does not exclude RVH 4, 2
- Use chest radiography - look for enlarged central pulmonary arteries (>15 mm in women, >16 mm in men at right interlobar artery), pruning, and RV enlargement on lateral view 1
- Confirm with right heart catheterization - required before initiating PAH-specific therapy 1, 5
Secondary ST-T abnormalities (ST depression and T-wave inversion in right precordial leads) should not be termed "strain" but rather "secondary ST-T abnormality." 1