Noninvasive evaluation of retrograde conduction times to avoid pacemaker-mediated tachycardia.

Pacemaker-mediated tachycardia is a potential complication of atrioventricular (AV) universal DDD pacemakers when retrograde ventriculoatrial (VA) conduction is slower than the postventricular-atrial refractory period of the pulse generator. The propensity for pacemaker-mediated tachycardia was noninvasively assessed in 17 patients with a unipolar DDD pacemaker using chest wall stimulation. Low amplitude stimuli were delivered to chest wall electrodes through a programmed stimulator. Using this method, 13 of the 17 patients were found to have absent VA conduction or VA conduction time less than the postventricular-atrial refractory period. In the four patients with noninvasively measured VA conduction time greater than the postventricular-atrial refractory period, sustained pacemaker-mediated tachycardia was induced. Reprogramming of pacemaker parameters prevented repeat induction of pacemaker-mediated tachycardia in only one of four patients. The three remaining patients had clinical pacemaker-mediated tachycardia and underwent pacemaker programming to the DVI mode. A total of 13 patients continue to use DDD mode after a mean follow-up period of 9.5 +/- 5.4 months. Invasive measurement of VA conduction was performed in 13 of the 17 patients. The noninvasive method accurately predicted the invasive measurement in each case. Noninvasive evaluation of VA conduction accurately predicts the propensity for pacemaker-mediated tachycardia under a variety of clinical conditions. Serial testing can be performed after pacemaker reprogramming or drug intervention. Noninvasive evaluation of retrograde VA conduction should predict most clinical episodes of pacemaker-mediated tachycardia.