Postoperative junctional ectopic tachycardia (narrow QRS with atrioventricular dissociation and ventricular rate faster than atrial rate) is self-limiting. It is usually controlled by decreasing the heart rate with moderate hypothermia and lower doses of inotropic agents, and by recovering atrioventricular synchrony by means of atrial or atrioventricular sequential pacing. In our patient, the tachycardia did not respond to the usual means or to amiodarone, and hemodynamic function became severely affected. The patient required extracorporeal membrane oxygenation for 72hours, during which time the ectopic tachycardia resolved. He was subsequently weaned and the outcome was favorable.