Effects of right ventricular outflow tract septum pacing on hemodynamics and cardiac function

AIM:To compare the effects of right ventricular outflow tract septum (RVOTS) pacing and right ventricular apex (RVA) pacing on hemodynamics, cardiac function and major adverse cardiovascular events, and to evaluate the long-term efficacy of RVOTS pacing. METHODS: Sixty-eight patients with chronic atrial fibrillation and with indications of pacing were randomly assigned to RVOTS pacing group (n=34) and RVA pacing group (n=34), and on-demand suppressed ventricular pacing mode (VVI) was used. All the patients were followed up for a mean of (27±10) months. QRS duration of electrocardiogram (ECG) in pacing, hemodynamics, cardiac function and the occurrence of major adverse cardiovascular events were observed and compared. RESULTS: The QRS duration of ECG in pacing in RVOTS group was significantly narrower than that in RVA group (P<0.05). At the end of follow-up, the left ventricular ejection fraction (LVEF) was lower (0.58±0.10 vs. 0.64±0.12, P<0.05) and the left atrium diameter (LAD) was larger ［(47±10) mm vs. (44±10) mm, P<0.05］ than those of the preoperative in RVA group. A similar trend was observed in the RVOTS group but no statistical differences were seen ［LVEF: 0.59±0.08 vs. 0.63±0.11; LAD: (47±7) mm vs. (45±7) mm］. At the end of follow-up, no statistical differences were observed between groups. Plasma levels of brain natriuretic peptide (BNP) were significantly higher than those of preoperative in the two groups at the end of follow-up ［RVA group: (292±168)ng/L vs. (200±70)ng/L, P<0.01, RVOTS group: (225±88) ng/L vs. (192±69) ng/L, P<0.05］. The increase in RVA group was significantly higher than that in RVOTS group during the same period (P<0.05). At the end of follow-up, the mean NYHA classification of cardiac function was higher significantly than that of the preoperative in RVA group (1.7±0.60 vs. 1.4±0.5, P<0.01). A similar trend was observed in the RVOTS group (1.5±0.7 vs. 1.3±0.5), but there were no statistical differences. No statistical differences were observed at the end of follow-up and no statistical differences were observed in hospitalization rate for heart failure, cerebral infarction and cardiovascular death between groups. CONCLUSION: Compared with RVA pacing, RVOTS pacing keeps a better electrical and mechanical synchronization in ventricle, thus reducing the damage of cardiac function and cardiac remodeling. RVOTS pacing thus is more physiological than RVA pacing.