FAILURE OF AUTOMATIC-MODE SWITCHING - RECOGNITION AND MANAGEMENT

Dual chamber pacing is desirable to optimize AV synchrony and to poten tially decrease the incidence of supraventricular tachyarrhythmias. Pa tients with alternating periods of both supraventricular tachyarrhythm ias and bradycardia pose a difficult challenge rr hen standard dual ch amber pacemakers are implanted. The automatic mode switching algorithm was introduced to prevent tracking of paroxysmal supraventricular tac hyarrhythmias and avoid the adverse hemodynamic and symptomatic conseq uences of a rapid ventricular response. In some cases, failure to mode switch map take place a hen the atrial signal during tachycardia is o f insufficient amplitude to be sensed. Failure to mode switch may also occur when the atrial signal periodically occurs in the atrial blanki ng period(s). In this article, we describe failure to mode sn itch in seven patients with paroxysmal supraventricular tachyarrhythmias after a Telectronics Meta DDDR 1254 device was implanted. Each patient had paroxysmal atrial flutter and/or atrial fibrillation and presented wit h either repetitive episodes of oscillation between atrial tracking an d mode switching to a nonatrial tracking pacing mode or complete failu re to mode su itch. Sis of seven patients were taking antiarrhythmic d rugs that resulted in slowing of the atrial cycle length. Pacemaker re programming nias required in each case to restore reliable mode switch ing during subsequent recurrences of the atrial tachyarrhythmias. We c onclude that careful pacemaker programming of patients with paroxysmal atrial flutter and the Telectronics Meta DDDR 1254 is necessary when patients are taking an antiarrhythmic drug that slows atrial cycle len gth.