Simultaneous electrical and mechanical alternans in pericardial effusion. Echocardiographic documentation.

A case of pericardial effusion and tamponade with echocardiographic documentation of both electrical and mechanical alternans is described. Alternation of the magnitude of the aortic valve opening reflected the mechanical alternation of the left ventricle. Analysis of the left atrial echoes may provide a possible explanation of the underlying mechanism. The cyclic variations in the magnitude of aortic opening in the weak beats, which are probably respiratory, may represent an echocardiographic counterpart of pulsus paradoxus. Echocardiograms of the aortic root and left atrium in pericardial effusion may help determine the true incidence of simultaneous electrical and mechanical alternans and may have potential value in the diagnosis of cardiac tamponade.