Abstract 16969: Assessment of the Electromechanical Window in Patients With Conventional Biventricular Pacing as Compared to Patients With Conduction System Pacing

Abstract

Introduction: The Electromechanical Window (EMW) is a validated measurement reflecting electromechanical coupling of the ventricles, and is defined as the difference between electrical and mechanical ventricular activation times. A larger (more negative) EMW is associated with worse clinical outcomes, especially greater arrhythmic risk, in various clinical conditions such as long QT syndrome, risk of drug-inducd torsade, hypertrophic cardiomyopathy, etc. Cardiac resynchronization therapy (CRT) can be achieved by conventional bi-ventricular pacing (BiVP) or conduction system pacing (CSP). We assessed the EMW in patients undergoing CRT via these 2 modalities. Methods: Total mechanical activation time was measured from the 5 chamber echocardiographic view as the interval (ms) from the onset of the Q wave to aortic valve closure (mean of 3 measurements). Total electrical activation time (QTcBazett interval, ms) was measured from 12 lead ECGs recorded within 24 hours of the echocardiogram. The EMW was calculated as the difference between the QTc and the mechanical ventricular activation time. Results: A total of 60 pts (BiVP=31, CSP=29) were analyzed. There was no significant difference between the heart rates during the ECG and the echocardiogram recorded within 24 hours of each other (74.6 ± 16.5 vs 71.5 ± 12.0 bpm, P=NS). The EMW was significantly more negative in patients with BiVP as compared to CSP (-99.5 ± 70.9 vs -55.2 ± 52.7 ms, P=0.03). When restricting the analysis to patients where the ECG and echocardiographic HRs were within 10 bpm of each other, the difference remained significant (P=0.03). Conclusions: Patients in whom CRT is achieved by CSP have less negative EMWs as compared to patients with BiVP. Based on the known association of more negative EMW with increased arrhythmic risk, these data, if confirmed in larger populations with correlation to clinical outcomes, add to the growing evidence to support CSP as the preferred modality for achieving CRT.