Pulsus alternans occurs in -
Constrictive pericarditis
Viral myocarditis
Hypokalemia
Myocardial infarction
pulses alternans is seen in 3 conditons a)large pericardial effusion b)left ventricular failure c)asthma so the answer is MI where there is left ventricular failure. Ref Harrison 20th edition pg 1523
C.V.S