The electrocardiogram in large pericardial effusion: the forgotten "P" wave and the influence of tamponade, size, etiology, and pericardial thickness on QRS voltage.

There are varying reports on the electrocardiogram in pericardial effusions. Some correlate low QRS voltage with tamponade and the size of the effusion while others do not. Low voltage also appears to vary with the etiology. There are no reports on the influence of pericardial thickness or changes in the P voltage. The authors studied 43 patients with large effusions of whom 26 had tuberculosis and the remaining had viral/idiopathic etiology. Pericardial thickness was measured at chest computed tomography. They found no correlation between the low QRS voltage and tamponade, size of the effusion, etiology, or pericardial thickness. Low voltage of the P wave and T-wave changes were more frequent than low QRS voltage.