A pacing parameter for controlling ventricular rate during atrial fibrillation: potential correlation to hemodynamic function

The irregular ventricular (V) rate of atrial fibrillation (AF) may contribute to adverse hemodynamics and symptoms. An algorithm that adjusts pacing rate based on RR interval mean absolute difference (MADIFF) to reduce AF V rate variability was tested. Previous algorithms used a fixed % of V pacing to change pacing rate. Patients with chronic AF, intact AV nodal conduction, and a pacemaker were studied during V rate stabilization (VRS) pacing and control. Previous work showed that cardiac output was inversely related to the % of RRs which were short relative to the preceding RR. VRS eliminated 74% and 81% of cycles more than 10% and 20% shorter than the preceding RR interval. MADIFF was better correlated to the % of cycles more than 10% and 20% less than the preceding RR than was % pacing. Hence, a MADIFF-based VRS algorithm reduced the % of short RRs and may be a better indicator/controller of hemodynamic performance in AF than % pacing.