Prolongation of the atrial refractory interval or programming to ventricular inhibited mode can successfully terminate spontaneous endless loop tachycardia starting after a normally-timed P wave.
May terminate endless loop tachycardia via atrial refractory adjustment; leaves open need for prospective validation before practice change.
Pacemaker-mediated endless loop tachycardia is usually caused by a P wave displaced from the physiologic position preceding a QRS complex to a time of atrial channel sensitivity after the QRS. Five cases are described of endless loop tachycardia starting after a normally-timed P wave, either spontaneous and preceding a ventricular stimulus or a P wave produced by an atrial channel stimulus followed by a ventricular stimulus and QRS complex. In each instance, the atrial refractory interval (ARI) was shorter than the retrograde conduction time. In four of the cases, prolongation of the atrial refractory interval after the ventricular event ended the tachycardias. In the fifth, in which the pulse generator could not be so programmed, the ventricular inhibited mode was required.
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Oseran et al. (1986) studied this question.
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