In-Vivo Measurements of Atrial Repolarization Alternans Based on Standard Pacemaker Technology

Introduction: It has been shown that repolarization alternans (Re-ALT), a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization DOR above a critical heart rate and promotes susceptibility to ventricular arrhythmias. It is unknown whether Re-ALT is measurable in the atria using standard pacemakers and whether Re-ALT plays a role in promoting AF. Methods: two DDD pacemakers (PM) with two right atrial (RA) leads were implanted in 3 male sheep (>60kg) after ablation of the AV junction. The 1st PM was used to deliver rapid pacing (400 beats) for measurements of RA Re-ALT, the 2nd one to record a broadband unipolar RA electrogram (EGM). Re-ALT was considered present when the 2 following conditions were fulfilled: 1) beat-to-beat alternation in T-wave apex amplitude (Ta) for >4 consecutive beats, and 2) statistically different distributions of odd and even Ta (p