Conduction time oscillations precede the spontaneous termination of human atrioventricular reciprocating tachycardia

Prior clinical research indicates that conduction slowing is the primary me chanism leading to the spontaneous termination of reentrant tachycardia in humans. Yet, some experimental models indicate that cycle length oscillatio ns and enhanced conduction are important prerequisites. The role of oscilla tions in conduction times and enhanced conduction in the spontaneous termin ation of human reentrant tachycardia has not been adequately investigated. The electrophysiologic features preceding the spontaneous termination of or thodromic atrioventricular (AV) reciprocating tachycardia (RT) were evaluat ed in 21 patients, each of whom had a sustained (>60 seconds) and a spontan eously terminating (greater than or equal to 10 beats and less than or equa l to 60 seconds) episode of AVRT during the same electrophysiologic study A trio-His, His-ventricular, interventricular, ventriculoatrial and atrial co nduction times were measured for each beat of spontaneously terminating AVR T and for paired beats of sustained AVRT. Beats of spontaneously terminatin g and sustained tachycardia were pooled and Hadi multivariate outlier analy sis was used to identify whether significant beat to-beat alterations in co nduction times preceded the spontaneous termination of reentry Cycle lengths of sustained (348 +/- 62 msec) and spontaneously terminating AVRT (351 +/- 70 msec) were similar. Significant beat to-beat oscillations in conduction times preceded the spontaneous termination of AVRT in 10 of t he 21 (48%) patients. An apparent enhancement in atrio-His or ventriculoatr ial conduction times immediately preceded the spontaneous termination of AV RT in 11 patients (52%), while an apparent conduction delay occurred in onl y 2 patients (10%). Moreover significant oscillations in conduction times w ere present in 9 of the 11 patients (82%) with enhanced conduction, but onl y in 1 of the 10 (10%) remaining patients (p = 0.002). Conduction time oscillations, which are related to apparent enhancement in atrio-His or ventriculoatrial conduction, frequently precede the spontaneou s termination of reentry in humans.