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Atrial ﬁbrillation reduces the atrial impedance amplitude during cardiac cycle: a novel detection algorithm to improve recognition of atrial ﬁbrillation in pacemaker patients

Aims In carriers of dual chamber pacemakers and implantable cardioverter-deﬁbrillators (ICD), detec- tion of atrial ﬁbrillation (AF) is crucial for adequate mode switch function and to avoid inappropriate shock delivery. Detection algorithms rely on the atrial rate and on the relationship of atrial to ventricu- lar intracardiac electrograms, but the relative portion of misclassiﬁed AF episodes remains high. Although myocardial impedance is a reliable indicator of contraction, little is known about atrial impe- dance as a marker of atrial arrhythmias. Methods During an electrophysiological study, we investigated the effect of induced AF on impedance at the right atrial free wall (RAFW) and right atrial appendage (RAA) in 20 patients. Using biphasic square-wave pulses (128 Hz, 200 m A / 15 m s), impedance changes were recorded during sinus rhythm (SR-1), atrial pacing at 120 beats / min, AF induced by rapid atrial burst pacing, and after spontaneous AF termination (SR-2). Results At the RAA, peak-to-peak impedance amplitude during cardiac cycle ( D Z ) dropped from 51.7 + 35.3 V (SR-1) or 49.6 + 30.6 V (pacing) to 24.6 + 22.0 V (AF, P (cid:2) 0.0005), and subsequently increased to 37.7 + 24.7 V (SR-2, P (cid:2) 0.0004 v. AF). At the RAFW, D Z changed from 16.2 + 15.5 V (SR-1) or 13.5 + 9.9 V (pacing) to 5.9 + 4.1 V (AF, P (cid:2) 0.003), and to 11.4 + 10.7 V (SR-2, P (cid:2) 0.015). Given a discrimination threshold of 65%, the sensitivity and the speciﬁcity of D Z to detect AF were 79 + 18 and 89 + 14%, respectively (95% conﬁdence interval). Conclusion AF causes D Z drop in pacemaker and ICD recipients. This impedance based algorithm can be used as an alternative method of AF detection.