Right Ventricular Apical Pacing in Patients With Preserved LVEF: Adverse Effects and Mechanisms.

Background: Long-term adverse cardiac effects of right ventricular (RV) pacing in patients with normal left ventricular (LV) ejection fraction (EF) are not well studied.

Objectives: The purpose of this study was to evaluate adverse effects of RV apical pacing in patients with normal LVEF.

Methods: Medical records of patients who had undergone RV apical pacemaker implantation for pacing indications and had an LVEF ≥50% were reviewed to determine the effect of RV pacing burden on LV systolic and diastolic function, mechanical dyssynchrony, heart failure hospitalization (HFH), and all-cause mortality.

Results: Of the 875 eligible patients from a single center, 459 patients met the inclusion criteria, 185 had <50% RV, and 274 had ≥50% RV pacing burden over a median 4.98 years (IQR: [3.2, 7.0]) of follow-up. LVEF in the ≥50% pacing group (median 63% [IQR: 58%, 67%]) and <50% group (median 64% [IQR: 60, 67]) decreased to 59.5% (IQR: [51%, 63%]) and 62% (IQR: [55%, 66%]), absolute median decrease 6.0 (IQR: [1, 10]) vs 3.0 (IQR: [4, 10]), P = 0.001 in the 2 groups, respectively. On multivariate analysis, RV pacing ≥50% (OR: 2.44 [95% CI: 1.43-4.16]; P = 0.001), baseline LVEF (HR: 0.95 [95% CI: 0.92-0.98]; P = 0.0008), relative decrease of >10% LVEF (HR: 1.73 [95% CI:1.09-2.75]), baseline E/e' ratio (HR: 1.07 [95% CI: 1.05-1.11]; P < 0.0001), and LV mechanical dyssynchrony by strain imaging performed in 193 subjects (HR: 1.031 [95% CI: 1.012-1.051]; P < 0.001) were predictors of HFH. Baseline mechanical dyssynchrony (HR: 1.024 [95% CI: 1.008-1.04]; P < 0.01), its worsening by 25% (HR: 2.077 [95% CI: 1.109-3.89]; P < 0.03), and baseline E/e' (HR: 1.063 [95% CI: 1.025-1.10]; P < 0.01) were predictors of all-cause mortality.

Conclusions: In patients with normal baseline LVEF, chronic apical RV pacing of ≥50% is associated with worse LV systolic function, LV mechanical dyssynchrony, and increases HFH.