Ventricular tachycardia "pleomorphism" induced by chest thump.

Figure 1 represents the electrocardiographic tracings obtained from a 59-year-old man admitted with an acute anterior wall myocardial infarction. Several hours following admission, ventricular tachycardia at a rate of 125 beats! mm appeared (Fig 1, top strip). This tachycardia was easily terminated by a chest thump. Five minutes later, ventricular tachycardia with identical morphology but faster rate (150 beats/mm) appeared (Fig 1, middle strips). Chest thump induced a premature ventricular complex (arrow) without terminating the ventricular tachycardia, but changed the QRS morphology from right axis to left axis deviation. With this new QRS morphology, the ventricular tachycardia rate