ELECTROCARDIOGRAPHIC CHANGES IN PERICARDIAL-EFFUSION

Objective: To investigate the association between ECG changes and the presence of pericardial effusion. Background: The ECG changes associat ed with pericardial effusion described in textbooks are based only on small series of human cases and data from animals. These changes inclu de low QRS voltage, electrical alternans, P wave changes, and T wave i nversion. Methods: All patients who had undergone 2 temporally separat e echocardiographic and ECG examinations, with 1 echocardiographic exa mination 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 statu s. Results: When 2 temporally separate ECGs for 46 patients were obtai ned 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 be ats per minute increasing to 106 beats per minute) and the percentage of patients with QRS voltage of less than 0.5 mV (10 percent increasin g to 22 percent) were associated with the development of effusion. A w eak 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 ind icating effusion from the 46 patients were compared with the ECGs from their age- and sex-matched control subjects, differences in heart rat e (106 beats per minute vs 80 beats per minute, respectively) and smal l changes in QRS voltage were associated with effusion status. No ECG variable was sensitive for the detection of pericardial effusion. Conc lusions: In both repeated-measures and case-control comparisons, ECG f indings are too few, subtle, insensitive, and nonspecific to be useful as indicators of the presence of pericardial effusion.