Introduction: Left ventricular (LV) pacing and activation are important factors affecting CRT response. Recent advances in multipolar LV leads offer variable pacing configurations. To evaluate activation patterns for various pacing vectors, a non-invasive biventricular mapping system (ECSYNC™, CardioInsight, OH) was used.
Methods: CRT patients (n=10, 8 males, age 65±12, QRSd=178±16ms) with previously implanted quadripolar LV leads ( Quartet™, St. Jude Medical, MN) were evaluated during various follow-up visits (8±5 mo post-implant). LV lead positions included 6 posterolateral, 3 anterior, and 1 infero-apical. Patients had heterogeneous etiology including ischemic and nonischemic cardiomyopathy and various conduction disorders. In each patient, activation patterns and electrical synchrony were evaluated for each of the 10 pacing vectors using ECSYNC.
Results: Visually assessable and quantifiable changes in activation and electrical synchrony were observed for each pacing vector. LV activation time varied by 31±11ms within each patient, but QRSd was not useful in delineating such changes and only varied by a nonspecific 14±4 ms. Figure shows a typical patient with delayed sinus LV activation and 3 variable pacing vectors. Vector 10 improves all but anterior LV, Vector 2 improves all but LV base, and Vector 8 provides best overall LV activation.
Conclusions: For the first time, patient specific variability in ventricular activation for various LV lead configurations were mapped and quantified using a novel CRT mapping system, demonstrating its potential for lead optimization.