Arrhythmias Caused by Dual-Chambered Pacing
The recent release ofDDD (and VDD) pulse generators with relatively short atrial refractory periods has set the stage for the development of endless loop or electronic reentry tachycardias because of the frequent occurrence of retrograde V A conduction in patients requiring permanent pacing. The absence of VA conduction during electrophysiologic testing at the time of implantation does not necessarily predict protection against endless loop tachycardia because VA conduction may occasionally become manifest only after implantation. Programmability of the atrial refractory period constitutes the most important pacemaker characteristic for the prevention of endless loop tachycardia. We have found chest wall stimulation a useful technique for the verification of the programmed upper atrial tracking rate, duration of the pacemaker atrial refractory period, and characterization of the predicted response to the upper programmed rate. Chest wall stimulation can initiate and terminate endless loop tachycardia in patients predisposed to this arrhythmia.
Potentially serious repetitive ventricular firing or tachycardia may occasionally be caused by a normally functioning DVI or DDD pulse generator. The problem of cross-talk or self-inhibition is unique to dual-chambered pacemakers and remains a potential problem despite the incorporation of a ventricular blanking period.
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