The Effect of Multipoint Pacing on the Left Ventricular Mechanics in Heart Failure Patients

Objective: Assess in heart failure patients the basic underlying (BL) LV mechanics, contractility & dyssynchrony and compare to RV pacing (R), single point LV biventricular pacing (B) and multipoint pacing (MPP).

Methods: 6 patients implanted with St. Jude Medical MPP devices were echoed in the first 24 hours after implantation, using each of the described pacing modes. For each mode LV circumferential, longitudinal strain, rotation & torsion was calculated.

Results: EF following implantation were , 34.5±7.8% (BL), 28.0±9.0% (R), 33.5±15.1% (B) & 38.0±15.8% (MPP). BL longitudinal strain had considerable segmental shortening variation of 4-16%. RV & B pacing changed the contraction pattern causing dyssynchrony & segmental shortening variation of 1-16%. MPP created homogeneous longitudinal segmental contraction of 6-11%. Pacing with all modalities caused significant decrease in global mean longitudinal strain compared to BL, 20.0±2.1% (BL), 8.5±1.0% (R), 9.7±1.3% (B) & 9.3±1.3% (MPP), (p<0.001). Segmental time to peak contraction varied during BL & RV pacing from 350 to 800 ms, and homogenized during B & MPP pacing to 350-450 ms. Circumferential analysis showed both apical & papillary muscles levels had poor shortening & strain, unchanged during pacing in all patients. Rotation of both the apex & the mitral valve (MV) changed significantly with MPP. Apical rotation of +2.9±10.7° (BL), changed to +4.6±5.5° (R), +3.0±6.4° (B), & +6.3±4.5° (M); and MV rotation changed from +3.0±0.2° (BL), to -1.2±4.5° (R), +1.2±4.8° (B) & +0.9±2.8° (MPP), increasing the torsion significantly from 3.3±12.7° (BL) to 4.7±5.8° (R), 4.0±5.3° (B), & 6.0±3.1° (MPP), (p<0.01).

Conclusion: MPP didn`t increase global LV strain or cardiac output, but has managed to homogenize the longitudinal LV segmental performance and increase the ventricular torsion. These findings might impact the intraventricular blood flow, vortex formation & emptying. More patients are enrolled & long time follow up is conducted.