Electrical alternans is seen in -: (A) Cardiac tamponade, (B) Restrictive cardiomyopathy, (C) Constrictive pericarditis, (D) Right Ventricular MI (RVMT
Answer is A. Electrical alternans is an electrocardiac phenomenon of alternation of QRS complex amplitude or axis between beats and a possible wandering base-line. It is seen in cardiac tamponade and severe pericardial effusion and is thought to be related to changes in the ventricular electrical axis due to fluid in the pericardium , as the hea essentially wobbles in the fluid filled pericardial sac . Ref Harrison 20,th edition pg 1543