McGill Case 177

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 76 | Next Case: McGill Case 178

This is an EKG rhythm and marker strip from a patient with a Medtronic model 7108 Minuet dual chamber pacemaker. The patient had intact A/V conduction, and with a long paced A/V interval, conducted paced atrial beats to the ventricle. The atrial pacing threshold was determined by pacing at a rate faster than the patient's own rate and decreasing the atrial pulse width until atrial capture was lost, and ventricular pacing occurred (the upper tracing). In spite of returning the atrial pulse width back to the last successful value, ventricular pacing continued . Slowing the pacing rate terminated ventricular pacing (the lower tracing) and ventricular pacing did not return when the pacing rate was speeded up again.