Magnet Application, a Cause of Persistent Arrhythmias in Physiological Pacemakers. Report of 2 Cases

Report of 2 cases. Magent application during routine pacemaker check‐up induced persistent arrhythmias in two patients with physiological pacemakers. One patient had received an atrial synchronous ventricular demand pacemaker (VDD) because of alternating second‐and third‐degree atrio‐ventricular block. During routine pacemaker follow‐up, a magnet was applied over the pulse generator to measure the pacemaker rate. This converted the system to fixed rate ventricular pacing at a rate of 65 bpm which resulted in retrograde atrial activation. When the magnet was removed the retrograde conducted P‐waves were sensed by the atrial amplifier and the ventricular output was triggered again, causing a re‐entry pacemaker tachycardia with a rate of 175 bpm. The tachycardia could be suppressed by applying a magnet once more, but the pulse generator had to be programmed in the VVI‐mode to prevent induction of the tachycardia again. A second patient had complete atrioventricular block and left heart failure. After three years of ventricular demand pacing, we decided to implant a DDD pacemaker because of persisting left heart failure and poor exercise tolerance. During a routine visit io the pacemaker clinic a magnet was applied over the pulse generator to measure the basic rate. The system was thus converted to fixed rate A‐V‐sequential pacing (DOO) which resulted in atrial flutter. When the magnet was removed and the pulse generator returned to its DDD mode, the atrial flutter was partially sensed by the atrial amplifier, resulting in a tachycardia with a variable rate up to 125 bpm. Fortunately we were able to terminate the atrial arrhythmia by applying the magnet again. In this patient fixed rate underdrive pacing stopped the atrial arrhythmia. (PACE, Vol. 5, September‐October, 1982)