[Comparative study of interventricular electrical and mechanical synchrony at different cardiac pacing sites].

Objective: To compare the different impacts of right ventricular apex, right ventricular outflow tract septum and left ventricular outflow tract septum region on interventricular electro-mechanical synchronization and assess the ideal pacing sites for maintaining the interventricular electro-mechanical synchronization.

Methods: A total of 30 patients without organic heart disease were operated with radiofrequency ablation at our hospital. The mapping electrodes were implanted post-operatively on the left ventricular posterior wall (LVPLW) and right ventricular anterior lateral wall (RVALW) respectively. And the ablation electrodes were placed subsequently in right ventricular apex, right ventricular outflow tract septum region and left ventricular outflow tract septum. The difference values were measured between transmission time from pacemaker to LVPLW, from pacemaker to RVALW and between aortic pre-ejection interval (APEI) and pulmonary artery pre-ejection interval (PPEI). Then their correlations were compared.

Results: When pacing at right ventricular apex, the difference value between transmission time from pacemaker to LVPLW and from pacemaker to RVALW was (34 ± 7) ms. And it was (18 ± 4) ms while pacing at right ventricular outflow tract septum region and (12 ± 4) ms at left ventricular outflow tract septum region. There was significant difference (P < 0.01). The absolute value of APEI-PPEI was (25 ± 5) ms at right ventricular apex, (13 ± 4) ms at right ventricular outflow tract septum region and (11 ± 3) ms at left ventricular outflow tract septum region. And there was significant difference (P < 0.01). The absolute value of APEI-PPEI was positively correlated with the change of LVPLW-RVALW (r = 0.993, P < 0.01). Left ventricular outflow tract septum pacing showed ABp and left ventricle end-systolic pressure significantly increased [(127 ± 23) mm Hg, (142 ± 22) mm Hg, P < 0.05], left ventricular end-diastolic pressure was significantly lower [(9 ± 3) mm Hg, P < 0.05].

Conclusion: Compared with right ventricular apical pacing and right ventricular outflow tract ventricular septal pacing, left ventricular outflow tract septum has a smaller impact on the electro-mechanical synchronization. It conforms more closely to the physiological pacing so that there is a higher synchronization of electrical and mechanical ventricular contractions.