R On T Pacing Phenomenon After His Bundle Pacing In Patients With Chronic Atrial Fibrillation And Slow Ventricular Response

ObjectiveIt was to illuminate the R on T pacing phenomenon after HIS bundle pacing in patients with chronic atrial fibrillation and slow ventricular response,and to find an appropriate approach to solve it.Methods18 patients who had a history of chronic atrial fibrillation with a slow ventricular response,normal activation interval(QRSd<120 ms)were screened for permanent HIS bundle pacing(HBP).After successful HBP,a right ventricular lead was implanted into ventricular septum.The HBP lead and ventricular lead were plugged into the atrial and ventricular ports of the pacemaker respectively.The pacemaker was programmed as DDD mode,PAV/SAV interval=250ms,and 60 beats per minute for low rate limit.The percentage of AP-VP at the first follow up and also the ECG during AP-VP mode at different AV interval was recorded.ResultsAverage heart rate of 18 patients was 50.06±7.40 beats per minute before the procedure.Permanent HBP was successful in all patients who received dual-chamber pacemakers.Acute pacing HBP threshold was 1.24±0.85V/0.5ms;sensed R wave potential was 3.97±1.60 mV.The HBP threshold was comparable(1.18±0.72V/0.4ms)at one month follow up.R on T pacing phenomenon could be recorded while the AV interval was set at 250ms.17 patients(94.4%)had a history of AP-VP,the average percentage of AP-VP was 2.86±4.58%.Ventricular stimulation delivered at the absolute refractory period and diminished the R on T phenomenon while the AV interval was programmed at 100-150ms.ConclusionR on T pacing phenomenon after HIS bundle pacing in patients with chronic atrial fibrillation is very common;a short AV interval of 100-150ms is an appropriate choice to avoid R on T pacing.