Correlation of right atrial enlargement on ECG to right atrial volume by echocardiography in patients with pulmonary hypertension

Previous attempts to validate ECG criteria for right atrial (RA) enlargement (RAE) have been limited by sample sizes and lack of accepted standards for measuring RA size. New guidelines have recommended that RA volume (RAV) be used to determine RA size. Since these guidelines were released, no studies have been published that correlate RAE by ECG to RAV using the new standards. We aimed to validate previously proposed ECG criteria for RAE, commonly called P pulmonale, and to establish whether a correlation exists between P wave amplitudes and RAV as determined by echocardiogram in patients from the pulmonary hypertension (PHT) clinic. We identified patients from the PHT clinic that had an echocardiogram and ECG done at most 30 days apart. We defined increased P wave amplitude as ≥2 mm in lead II and ≥1 mm in lead V1. The RA was determined to be enlarged if the RAV index (RAVI) was ≥39 mL/m² for men and ≥33 mL/m² for women. Patients were stratified into four groups: those with P II ≥ 2 mm, those with P V1 ≥ 1 mm, those that met both criteria, and those that met neither. Right atrial volumes were then compared. Sixty-three patients were included in the study (7 men, 56 women). Three men and 36 women had an ECG that met criteria for P pulmonale. Five men and 28 women had an enlarged RA on echocardiogram. Sixty-nine percent of ECGs that met criteria for RAE were associated with increased RAV by echocardiogram. The specificity of each of the ECG criteria for P pulmonale at detecting RAE was 100% for men. The criterion with the highest specificity among women was P II ≥ 2 mm AND P V1 ≥ 1 mm (94%). The least specific criterion for women was P II ≥ 2 mm (70%). The sensitivity of each criterion was much lower. The most sensitive criteria for men and women were P V1 ≥ 1 mm (66.6%) and P II ≥ 2 mm (48%), respectively. The correlation of P wave amplitude in leads II and V1 and RAVI was not statistically significant for any of the ECG criteria for P pulmonale. In patients from the PHT clinic, the specificity of P pulmonale for detecting RAE is high, but the sensitivity is relatively low. These results suggest that in PHT, P pulmonale can be used to confirm that the RA is enlarged, but it is not a reliable test for diagnosing RAE.