Comparison of left ventricular systolic function and mechanical dyssynchrony using equilibrium radionuclide angiography in patients with right ventricular outflow tract versus right ventricular apical pacing: A prospective single-center study.

BACKGROUND: Chronic ventricular pacing is known to adversely affect left ventricular (LV) function. Studies comparing right ventricular outflow tract (RVOT) pacing with RV apical (RVA) pacing have shown heterogeneous outcomes. Our aim was to objectively assess LV function and mechanical dyssynchrony in patients with RVOT and RVA pacing using equilibrium radionuclide angiography (ERNA).

METHODS: Fifty-one patients who underwent permanent pacemaker implantation and had normal LV function were prospectively included. Twenty-nine patients had pacemaker lead implanted in the RVOT and 22 at the RVA site. All patients underwent ERNA within 5 days post-pacemaker implantation and follow-up studies at 6 and 12 months. Standard deviation of LV mean phase angle (SD LV mPA) expressed in degrees, which was derived by Fourier first harmonic analysis of phase images, was used to quantify left intraventricular dyssynchrony.

RESULTS: No significant difference was observed between the two groups with respect to indication (P = .894), Type/mode (P = .985), and percentage of ventricular pacing (P = .352). Paced QRS duration was significantly longer in RVA group than RVOT group (P = .05). There was no statistically significant difference between the RVA and RVOT groups at baseline with respect to LVEF (P = .596) and SD LV mPA (P = .327). Within the RVA group, a significant decline in LVEF was observed over 12-month follow-up (from 57.3% ± 5.32% to 55.6% ± 6.25%; P = .012). In the RVOT group, the change in LVEF was not statistically significant (from 56.7% ± 4.08% to 54.3% ± 6.63%; P = .159). No significant change in SD LV mPA was observed over 12-month follow-up within the RVA group (from 10.5 ± 2.58° to 10.4 ± 3.54°; P = 1.000) as well as in the RVOT group (from 9.7 ± 3.28° to 9.4 ± 2.85°; P = .769). However, between the RVA and RVOT groups, no significant difference was observed at 12-month follow-up in terms of LVEF and dyssynchrony (LVEF P = .488; SD LV mPA P = .296).

CONCLUSION: No significant difference was observed between RVOT and RVA groups with regard to LV function and synchrony over a 12-month follow-up. RVOT pacing offers may lead to better preservation of LV function on longer follow-up.