Purpose: Assess QRS metrics derived from 3D VCG to evaluate the improvement in electrical synchrony provided by SyncAV during bi-ventricular (BiV) pacing in a large patient population.
Methods: Patients previously implanted with a CRT device underwent 12-lead surface ECG recordings. 3D VCG metrics were derived by a blinded observer from the ECG using the Kors matrix during the following settings: intrinsic ventricular activation, BiV nominal (140/110 ms sensed/paced AVD), and BiV + SyncAV Opt (patient-optimized offset resulting in the greatest QRS narrowing).
Results: One hundred patients (71% male, 40% ischemic, 65% LBBB, ejection fraction 32±9%) completed VCG QRS assessment. The 12-lead ECG, x/y/z projected VCG, and vector magnitude (VM) for BiV nominal and BiV + SyncAV Opt are shown for a representative patient (left panels). As shown by the bar graphs (right panel), QRS duration was narrowed successively from (166±24 ms) during intrinsic conduction to 137±23ms during BiV nominal pacing, and (122±22ms, during BiV + SyncAV Opt. Likewise, 3D QRS amplitude during intrinsic activation (1.47±0.55mV) was reduced with BiV nominal pacing (1.14±0.49mV) and tended towards a further decrease with BiV+SyncAV Opt (1.09±0.48mV). 3D QRS area during intrinsic activation (90±42 mV.ms) also decreased with BiV nominal pacing (65±39 mV.ms), with further reduction achieved by BiV + SyncAV Opt (53±30 mV.ms).
Conclusion: VCG measurements support the evidence that BiV pacing with an optimized SyncAV offset improves electrical synchrony beyond conventional CRT with nominal settings. Additional, larger studies are needed to further evaluate the relationship between the electrical synchrony achieved with SyncAV and long-term patient outcome.