CP12: OPTIMIZED LV PACING BY FUSION WITH INTRINSIC RIGHT BUNDLE ACTIVATION COMPARED TO BIVENTRICULAR PACING AND THE EFFECT ON THE RIGHT VENTRICULAR ELECTROGRAM

In patients with normal atrioventricular (AV) conduction left ventricular (LV) pacing is superior to biventricular (BiV) pacing, due to intrinsic conduction over the right bundle branch during LV pacing.

To investigate the hemodynamic effect of LV pacing and its association with the right ventricular (RV) electrogram (EGM) as an indicator of ventricular fusion.

A BiV pacing system was implanted in 13 patients (8 males, age 66.8±10.2 years) with heart failure NYHA class III-IV, ejection fraction 21.1± 5.6% and sinus rhythm with normal AV conduction. The hemodynamic effect of LV, BiV simultaneous and (BiVsim) optimized V-V interval (BiV opt) pacing was evaluated by invasive measurement of LV dP/dt max with different AV intervals. A 12 lead ECG and the RV EGM obtained by pacemaker telemetry were recorded to evaluate fusion.

The RV EGM showed a dominant R wave with AV intervals starting 30 ms below the intrinsic PR time (RV R-wave), changing to a configuration with a dominant S wave at short AV delays where no fusion is present (RV S-wave). In between an intermediate RV EGM morphology is recorded (RV-inter). LV dP/dtmax for baseline was 756±167, LV (RV R-wave) 936±209, LV (RV inter) 856±193, LV (RV S-wave) 787±176, BiV sim 896±217 and BiVopt 936±216 mmHg/s.

LV pacing with the optimal AV interval (LV opt) is superior to BiV (p=0.04) and equal to BiVopt pacing. A change in the RV EGM from a prominent R wave to an intermediate morphology during LV pacing is associated with a significant decrease in LV dP/dtmax (p=0.0022). The change in the RV EGM indicates a shift in the extent of fusion from LV pacing.