Notes on ventricular tachycardia occurring during magnet waving and on the function of the Omni-Ectocor pacemaker.

Magnet waving was performed in a patient with a normally functioning, program-mable, QRS-inhibited (VVI) pacemaker (Omni-Stanicor, Cordis Corporation), which was implanted for sick sinus syndrome. This procedure resulted in reversion to an asynchronous, nonsensing (irregular VOO) mode of operation with uneven stimulus-to-stimulus intervals. A short run of ventricular tachycardia occurred when a stimulus fell on the T wave of the preceding ectopic ventricular beat. This tachycardia was short-lived and was probably terminated by a single pacemaker stimulus. It is also suggested that magnet waving and external chest wall stimulation in patients with Omni-Ectocor and Starr--Edwards pacemakers require further study and that electrocardiograms recorded from patients in whom they have been implanted have to be analyzed taking into consideration that these pacemakers have features common to both, QRS-triggered (VVT), and QRS-inhibited (VVI) pacemakers.