Effect of the atrial blanking time on the detection of atrial fibrillationin dual chamber pacing

Patients with paroxysmal atrial fibrillation (PAF) and dual chamber pacemak ers frequently have short postventricular atrial blanking times and sensiti ve atrial sensing thresholds used to provide reliable detection and mode sw itching during AF. However, short atrial blanking times increase the risk o f atrial sensing of ventricular far-field signals. We evaluated if the leng th of the atrial blanking time influences the detection of AF. The study in cluded ten patients with a VDDR (n = 7) or DDDR system (n = 3), who present ed with AF at 18 follow-up visits. Bipolar atrial sensing was programmed to the most sensitive value. Atrial blanking times were programmed from 100 t o 200 ms in 25-ms steps in each patient. Using marker annotation, the follo wing parameters were measured at ten consecutive ventricular beats: VAF = t he interval between ventricular events; and XAF = the interpolated number o f atrial-sensed atrial-sensed events between two ventricular events; and XA F = the interpolated number of atrial-sensed events during atrial blanking time. The intervals between ventricular events and between atrial-sensed ev ent markers showed no significant differences for the five blanking times t ested. There was no significant influence of the atrial blanking time onto the measured parameters (least square means +/- standard error) with VAF be tween 281 +/- 12 and 300 +/- 12 ms (P = NS), AFs between 3.4 +/- 0.2 and 3. 6 +/- 0.2 beats (P = NS) and XAF between 1.84 +/- 0.12 and 2.03 +/- 0.12 be ats (P = NS). At ventricular rates < 100/min, the atrial sensing of AF in d ual chamber pacemakers demonstrated no evidence for deterioration by an inc rease of the atrial blanking time from 100 to 200 ms. Thus, the risk of ven tricular far-field sensing may be reduced without compromising atrial sensi ng.