Dyssynchrony and Right Ventricular Apical Pacing Background Right ventricular apical (RVA) pacing may induce left ventricular (LV) dyssynchrony. The long-term prognostic implications of induction of LV dyssynchrony were retrospectively evaluated in a cohort of patients who underwent RVA pacing. Methods A total of 169 patients (62 ± 13 years, 69% male) with high RVA pacing burden were included. Echocardiographic evaluation of LV volumes, ejection fraction, and dyssynchrony were performed before and after device implantation. LV dyssynchrony was assessed by 2-dimensional radial strain speckle tracking echocardiography. Based on the median LV dyssynchrony value after RVA pacing, the patient population was dichotomized (induced and noninduced LV dyssynchrony groups) and was followed up for the occurrence of all-cause mortality and heart failure (HF) hospitalization. Results Baseline mean LV ejection fraction was 51 ± 11%. Median LV dyssynchrony value was 40 ms (12-85 ms) before RVA pacing and increased to 91 ms (81-138 ms) after a median of 13 months (3-26 months) after RVA pacing. Median follow-up duration was 70 months (interquartile range 42-96 months). Patients with induced LV dyssynchrony, defined as LV dyssynchrony value superior to the median at follow-up (≥91 ms), showed higher mortality rates (5% and 27% vs. 1% and 3% at 3 and 5 years follow-up; log-rank P = 0.003) and HF hospitalization rates (18% and 24% vs. 3% and 4% at 3 and 5 years follow-up; log-rank P < 0.001) than patients with LV dyssynchrony <91 ms after RVA pacing. A multivariate model was developed to identify independent associates of a combined endpoint of all-cause mortality or HF hospitalization. Induction of LV dyssynchrony was independently associated with increased risk of combined endpoint (HR [95% CI]: 3.369 [1.732-6.553], P < 0.001). Conclusion Induction of LV dyssynchrony by RVA pacing is associated with worse long-term mortality and increased HF hospitalization rates.