Abstract 3783: Non-uniform Left Ventricular Work Load in Left Bundle Branch Block -Improved, but Not Equalized With Biventricular Pacing
Background: For bi-ventricular pacing (BVP) to be most efficient and cause reverse remodeling in patients with left bundle branch block (LBBB), there should be electrical resynchronization as well as equalization of work distribution within the left ventricle. In the present study we investigate regional work distribution during LBBB and how it was modified by BVP.
Methods: In 5 anesthetized dogs with micromanometers we measured dimension changes with sonomicrometry. Regional electrical activation was defined as onset R in intramyocardial electromyograms (IM-EMG). Segmental work was calculated as area of the pressure-segments length loops. Measurements were performed during baseline, LBBB by RF ablation and BVP.
Results: During LBBB segmental work was markedly reduced in the early-activated antero-septal (net passive) and posteroseptal walls (Fig 1⇓). In the late-activated postero-lateral wall, however, segmental work was increased relative to baseline. BVP during LBBB reduced the heterogeneous timing of electrical activation of the LV free wall from 37±22 to 17±15ms (mean±SD). Segmental work became more evenly distributed, but there was still substantial non-uniformity, with a 27% increase of segmental work in the postero-lateral wall and a 36 % reduction in the anteroseptal wall relative to baseline (Fig 1⇓).
Conclusion: BVP leads to a greater degree of LV electrical and mechanical synchrony in LBBB. However, segmental work during BVP still shows an uneven distribution.