McGill Case 381

This case report is kindly provided by Michael Rosengarten from McGill and is part of the McGill Cases. These cases come from the McGill EKG World Encyclopedia. Previous Case: McGill Case 380 | Next Case: McGill Case 382

This is a tracing from a patient in the pacemaker clinic. The pacemaker was set to VDD mode. There is group beating. The rhythm begins with a ventricular paced beat which occurs at the pacing interval as set by the programmed rate. There is then a retrograde P that is sensed by the atrial channel of the pacemaker and a pacemaker mediated tachycardia begins. The tachycardia stops probably because a retrograde P was blocked. Lack of capture of the atrium either seen with the VDD mode of pacing or with failure of the atrial pacing lead to capture is a mechanism for the initiation of pacemaker mediated tachycardia.