Objectives: This study was conducted to evaluate the sensitivity and specificity of traditional electrocardiographic (ECG) criteria for right atrial enlargement and identify improve criteria, using quantitative two-dimensional echocardiography.
Background: Traditional ECG criteria for right atrial enlargement, such as P pulmonale, have been increasingly criticized as insensitive and nonspecific. Quantitative two-dimensional echo-cardiography has been shown to be a useful method for evaluating atrial size.
Methods: Hospitalized patients with mild, moderate and severe right atrial enlargement were selected from our laboratory's data base and compared with age- and gender-correlated hospitalized control subjects. After exclusions, 100 patients with right atrial enlargement and 25 control patients remained. Planimetric measurement of right atrial volumes was accomplished by two independent observers using the single-plane method of discs algorithm. Electrocardiograms were independently evaluated for current and newly proposed right atrial enlargement criteria.
Results: Fifty-two patients (52%) were in sinus rhythm, 41 were in atrial fibrillation, 5 were in atrial flutter, and 2 were in ectopic atrial rhythm. All control subjects were in sinus rhythm. The right atrial volume for the control group was 35.0 +/- 7.4 ml (mean +/- SD), with a narrow, roughly normal distribution. The right atrial volume for the patient group was 147.6 +/- 69.1 ml (median 127.2) in a wide, skewed distribution. The difference of mean values was highly significant (p = 0.0001). Right ventricular enlargement was found to some degree in all patients with right atrial enlargement. The most powerful predictors of right atrial enlargement were a QRS axis > 90 degrees, a P wave height in lead V2 > 1.5 mm and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. P pulmonale detected only 6% of patients with right atrial enlargement.
Conclusions: Using quantitative two-dimensional echocardiography, we found that most previously reported ECG criteria for right atrial enlargement have low predictive power. The best predictors of right atrial enlargement were a P wave height > 1.5 mm in lead V2 and, as new criteria, a QRS axis > 90 degrees and an R/S ratio > 1 in lead V1 in the absence of complete right bundle branch block. The combined sensitivity of these three criteria was 49%, with preservation of 100% specificity. Further studies are needed to prospectively validate these findings.