Pacing-Induced Electrophysiological Remodeling in Hypertrophic Obstructive Cardiomyopathy—Observations on Cardiac Memory.

NOWINSKI, K.,et al.: Pacing-Induced Electrophysiological Remodeling in Hypertrophic Obstructive Cardiomyopathy—Observations on Cardiac Memory. Background:Hypertrophic cardiomyopathy carries an increased risk for sudden cardiac death. While pacing therapy reduces the left ventricular outflow tract gradient and improves symptoms in a subgroup of hypertrophic obstructive cardiomyopathy (HOCM) patients, its electrophysiological consequences are unknown and were therefore assessed in this prospective study.Methods and Results:Fifteen consecutive HOCM patients were studied and compared with 14 patients without HOCM paced because of sinus bradycardia. ECG intervals were measured before pacemaker implantation and after≥3 months of DDD pacing in HOCM patients and≥5 weeks in controls. Both groups showed similar ECG signs of cardiac memory development. In HOCM patients, with baseline QTc 447± 33 ms, cardiac memory development was not associated with any significant changes in ECG intervals. In contrast, baseline repolarization in control patients was significantly prolonged by 6% (QTc 429± 33 vs 454± 46 ms; P<0.05). Furthermore, in HOCM patients repolarization was 7% shorter during DDD pacing compared to sinus rhythm (JTc 329± 25 vs 353± 21 ms; P<0.05), despite a significantly prolonged ventricular activation time (QRS duration 155± 16 vs 91± 9 ms; P<0.01).Conclusions:Importantly, the development of cardiac memory-induced different repolarization responses depending on baseline structure and electrophysiology. In HOCM patients repolarization was shorter during right ventricular apical pacing than during normal activation despite prolonged activation time.(PACE 2005; 28:561–567) [ABSTRACT FROM AUTHOR]