Low electrocardiographic voltage in pericardial effusion.

Although low ECG voltage has been associated with pericardial effusion, its diagnostic usefulness in such patients is unclear. When we examined the relationship between the volume of pericardial effusion and low voltage in 28 patients who underwent pericardial drainage, 14 patients exhibited low voltage (sum of limb lead QRS amplitudes of 30 mm or less). In eight patients, the QRS amplitude was 5 mm or less in each of the standard leads (absolute low voltage). There was no significant correlation between the volume of the effusion and the QRS amplitude (r = -0.30). This correlation did not improve (r = -0.37) when patients with left ventricular hypertrophy were excluded. Following pericardial drainage, the QRS amplitude increased in 21 of 24 patients and decreased in three. Low voltage persisted in nine patients; the pericardium was thickened in seven of the nine. Analysis of the sensitivity and specificity revealed acceptable sensitivity only with large effusions and no left ventricular hypertrophy. Absolute low voltage appeared to be specific in the diagnosis of moderate and large effusions among patients with pericardial effusion selected for this study.