BACKGROUND: The effect of paced-QRS (p-QRS) duration on long-term outcomes is unclear, so we assessed the association between p-QRS duration and cardiac events. METHODS AND RESULTS: We enrolled 187 patients (103 males, mean age: 77±12 years) who underwent pacemaker implantation between 2018 and 2021. During the median follow-up period of 972 days (761-1,292 days), 18 patients experienced cardiac events (1 cardiac death, 17 heart failure hospitalizations). The p-QRS duration was longer in the cardiac event group than in the noncardiac event group (162±17 vs. 148±17 ms, P=0.005). Receiver operating characteristic curve analysis identified 149 ms as the optimal cutoff value for predicting cardiac events (area under the curve, 0.72). Kaplan-Meier analysis showed better outcomes for mid-range p-QRS duration (≤149 ms, n=89) compared with long p-QRS duration (>
149 ms, n=98) (P=0.005). Multivariate Cox hazard analysis indicated a good outcome with mid-range p-QRS duration (hazard ratio: 0.28, 95% confidence interval: 0.06-0.88, P=0.029). CONCLUSIONS: A p-QRS duration of ≤149 ms was associated with a reduction in cardiac events. Therefore, it may serve as a target index of success in right ventricular pacing.