RESUMO
<p><b>AIM</b>To approach the effects of multi-site synchronous ventricular pacing on myocardial mechanics and cardiac work.</p><p><b>METHODS</b>Five modes of multi-site synchronous ventricular pacing were randomly performed in 12 dogs with anesthetized, opened chest and artificial-ventilation. Some parameters were measured simultaneously including: the peak of left ventricular pressure rise and fall (+/- dp/ dt(max)), the time constant of left ventricular relaxation(tau), the muscle tensile force in left/right ventricular wall (V-tensile force, V-TF), SV, LVSW and RVSW.</p><p><b>RESULTS</b>The myocardial systolic mechanical parameters: +dp/dt(max) and LV-TF of cHisB-LVPL and RVA-LVPL pacing by biventricular pacing modes were increased than that of cHisB-RVA pacing in right ventricular bifocal pacing mode. +dp/dt(max) in above two groups of biventricular pacing was increased than that in cHisB-RVA pacing. Tau value of cHisB-LVPL and RVA-LVPL pacing modes were shorted than that of cHisB-RVA pacing. The above parameters of cHisB-RVA-LVPL and cHisB-RVA-LVA biventricular trifocal pacing were superior to that of cHisB-LVPL and RVA-LVPL biventricular pacing. The +dp/dt(max), LV-TF and RV-TF of cHisB-RVA-LVPL pacing were increased as compared with that of cHisB-RVA-LVA pacing (P > 0.05). The -dp/dt(max) in cHisB-RVA-LVPL pacing were increased by 6.0% and tau value was shorted by 3.7% compared with those in cHisB-RVA-LVA pacing (P > 0.05). SV, LVSW and RVSW of cHisB-LVPL and RVA-LVPL biventricular pacing were increased than those of cHisB-RVA bifocal pacing. The above parameters of cHisB-RVA-LVPL pacing were increased than that of cHisB-RVA-LVA and cHisB-LVPL pacing.</p><p><b>CONCLUSION</b>It was explained that the cHisB-RVA-LVPL biventricular trifocal sites synchronous pacing mode would increase the velocity of ejection and filling during myocardial contraction and relaxation and enhance cardiac work by maintaining normal VSS.</p>