976-12 Reduced Reflex Vagal Activity in Patients with AV Nodal Reentrant Tachycardia Compared to Patients with Atrioventricular Reentrant Tachycardia

Abstract

Decreased heart rate variability, a manifestation of reduced tonic vagal activity. has been reported following radiofrequency catheter ablation (RFCA) for AV nodal reentrant tachycardia (AVNRT). Disruption of parasympathetic fibers in the posteroseptal region is the proposed mechanism. Baroreflex sensitivity (BRS). an index of reflex vagal activity. has not been evaluated in patients with AVNRT. We studied BRS prior to and immediately following RFCA in 20 patients with AVNRT(age 13–65 years, mean 42; 15 females. 5 males). Fourteen patients with atrioventricular reentrant tachycardia (AVRT) and free wall accessory pathways (age 14–46 years. mean 25; 6 females. 8 males) were evaluated as controls (RFCA site far from posteroseptal region I. BRS (msec/mmHg) was assessed with continuous femoral artery blood pressure (BP) and ECG recordings during the bolus administration of phenylephrine (400 μg). BRS was calculated as the slope of the change in cycle length vs the change in systolic BP during the first sustained rise in BP. At baseline. prior to RFCA. mean BRS for patients with AVNRT was significantly less than for patients with AVRT (8.3 ± 5.9 vs 22.1 ± 10.3; P < 0.0002). This difference remained significant when controlled for age (p < 0.0002) and male gender (p < 0.0003). but not for female gender (p < 0.09). Following RFCA there was no significant change in BRS for patients with AVNRT (9.3 ± 7.6) or AVRT (17.3 ± 9.6) compared to pre-RFCA values. This comparison remained insignificant when controlled for age or gender. These results suggest that in the baseline state, patients with AVNRT have lower reflex vagal activity than patients with AVRT. Reduced reflex vagal activity may contribute to the development of sustained AVNRT in patients with dual AV nodal physiology. RFCA did not alter BRS in either patient group.