Electrocardiographic changes in pericardial effusion.

OBJECTIVE: To investigate the association between ECG changes and the presence of pericardial effusion.

BACKGROUND: The ECG changes associated with pericardial effusion described in textbooks are based only on small series of human cases and data from animals. These changes include low QRS voltage, electrical alternans, P wave changes, and T wave inversion.

METHODS: All patients who had undergone 2 temporally separate echocardiographic and ECG examinations, with 1 echocardiographic examination indicating the presence and the other indicating the absence of pericardial effusion were identified (n = 46). These patients were age- and sex-matched to 46 patients without effusion (control subjects). Pericardial effusion was classified echocardiographically as small (n = 28), moderate (n = 13), and large (n = 5). The ECG variables were independently measured by two investigators blinded to effusion status.

RESULTS: When 2 temporally separate ECGs for 46 patients were obtained in a repeated-measures fashion (1 obtained during the absence and the other during the presence of effusion; median time interval, 1.24 months), only the mean heart rate in patients with sinus rhythm (98 beats per minute increasing to 106 beats per minute) and the percentage of patients with QRS voltage of less than 0.5 mV (10 percent increasing to 22 percent) were associated with the development of effusion. A weak correlation (r = 0.296) was noted between QRS voltage and effusion size. Electrical alternans occurred only in one of the five patients with a large effusion but in no others. In addition, when the ECGs indicating effusion from the 46 patients were compared with the ECGs from their age- and sex-matched control subjects, differences in heart rate (106 beats per minute vs 80 beats per minute, respectively) and small changes in QRS voltage were associated with effusion status. No ECG variable was sensitive for the detection of pericardial effusion.

CONCLUSIONS: In both repeated-measures and case-control comparisons, ECG findings are two few, subtle, insensitive, and nonspecific to be useful as indicators of the presence of pericardial effusion.