Comparison of right ventricular apex and right ventricular outflow tract septum pacing in the elderly with normal left ventricular ejection fraction: long-term follow-up

Background: Whether right ventricular outfow tract septum (RVOTS) pacing is superior to right ventricular apex (RVA) pacing with respect to left ventricular synchrony, cardiac function, and remodelling in the elderly with normal left ventricular ejection fraction (LVEF), is still unknown. Aim: To assess the impact of RVOTS vs. RVA pacing on the cardiac performance of the elderly with normal LVEF during a long-term observation. Methods: From 2007 to 2010, 65 patients with standard pacing indications for permanent pacing were recruited and randomised to receive RVA (32 patients) or RVOTS pacing (33 patients). Over a median 28 months' follow-up, available data was summarised, including New York Heart Association (NYHA) functional class, echocardiographic and pacing parameters, axis, QRS duration and plasma B-type natriuretic peptide (BNP) level. Then these values were compared between the RVA group and the RVOTS group, as well as between pacemaker pre- and post-implantation in the RVA group and in the RVOTS group, respectively. Results: There were no significant differences in baseline characteristics between the RVA group and the RVOTS group. The median pacing durations did not differ significantly between the groups (31.5 months in the RVA group vs. 28 months in the RVOTS group, p = 0.728). Compared to the baseline values, LVEF decreased with RVA pacing (from 59.5 +/- 6.21 to 54.22 +/- +/- 8.73, p = 0.001), but LVEF did not markedly vary in the RVOTS group (57.82 +/- 6.06 and 56.94 +/- 5.54, p = 0.152). The number of patients with moderate tricuspid valve regurgitation remarkably increased in the RVA group, from six (18.75%) patients to 10 (31.3%) patients, preoperatively to postoperatively (p = 0.046), but this change was not statistically significant in the RVOTS group. Compared to the RVOTS group, NYHA functional class had a deteriorated tendency in the RVA group (p = 0.071). After the implantation, the increase of median BNP level was observed in the RVA group (35 pg/mL at preimplantation and 50 pg/mL at the end of follow-up, p = 0.007); No significant change was obtained in the RVOTS group (36.4 pg/mL at pre-implantation vs. 38 pg/ml at the end of follow-up, p = 0.102). Compared to the RVA pacing group, the mean QRS width narrowed substantially in the RVOTS pacing group (from 143.56 +/- 12.90 to 105.52 +/- 15.21, p = 0.000). In terms of the end diastolic and systolic diameters of the left ventricular, there were no statistical variations observed during the follow-up. Conclusions: Permanent RVA pacing in elderly patients with normal LVEF led to left ventricular systolic function deterioration denoted by lower LVEF and higher BNP level. When compared to RVA pacing, RVOTS pacing had no remarkable benefit in terms of preventing cardiac remodelling.