Introduction: Right ventricular (RV) pacing causes changes in the heart’s electrical and mechanical activation patterns. QRS duration is a useful surrogate marker of electrical dyssynchrony; longer QRS duration during RV pacing indicates poor prognosis. However, the mechanisms underlying longer QRS duration during RV pacing remain unclear; hence, we investigated factors predicting QRS prolongation during RV pacing. Methods and Results: We enrolled 211 patients who underwent catheter ablation for supraventricular tachyarrhythmia and showed no bundle-branch-block. Three-dimensional mapping for QRS duration during RV pacing from the RV outflow to RV apex was performed, and the difference in QRS duration was analyzed. The predisposing factors causing QRS >160 ms during RV apical pacing were also analyzed. QRS durations at baseline and during RV pacing from the RV outflow and at RV apex were 85.0±7.5 ms, 163.7±17.1 ms, and 156.2±16.1 ms, respectively. With respect to QRS duration, there was a significant correlation between RV outflow and RV apical pacing (r=0.658, p<0.001). The difference in QRS duration between RV outflow and apex in each patient was only 12.5±10.4 ms. Logistic multivariable regression analysis identified baseline QRS duration [odds ratio (OR) 1.24, 95% confidence interval (CI) 1.15 to 1.33, p<0.01], interventricular septum thickness (OR 1.20, 95% CI 1.02-1.40, p=0.025), left atrial diameter (OR 1.08, 95% CI 1.01-1.16, p=0.024), and E/e’ (OR 1.23, 95% CI 1.12-1.35, p<0.01) as significant predictors of prolonged QRS duration during RV apical pacing. Conclusion: QRS duration during RV pacing largely depends not on the pacing site, but on underlying structural heart diseases.

Introduction: Early recurrence (ER) of atrial fibrillation (AF) is defined as the recurrence of atrial tachyarrhythmias within 3 months after AF ablation, however, this definition is based on data from the era of radiofrequency catheter ablation (RFCA), without contact force (CF) technology. We investigated the significance of ER as a risk factor for late recurrence (LR) in paroxysmal AF (PAF) patients treated with CF and non-CF-guided ablation. Methods and Results: We studied 395 patients with PAF who underwent RFCA. Of these, 97 patients underwent RFCA without CF technology (Non-CF group) and 298 underwent with CF technology (CF group). Over a 2-year post-ablation follow-up period, LR occurred in 54 of 97 (55.7%) patients in the Non-CF group, and in 105 of 298 (35.2%) patients in the CF group. ER had a more significant relationship with LR in the CF than in the Non-CF group, and all patients in the CF group with ER in the 3rd month developed LR. Conclusion: ER in PAF patients who have undergone CF-guided ablation have a greater risk of LR than those who have undergone non-CF-guided ablation. ER in the 3rd month after CF-guided ablation may indicate an absolute risk of LR. Blanking period could be defined as 2 months in the CF era.

A 65-year-old male underwent a second ablation procedure for recurrent paroxysmal atrial fibrillation (AF). Twelve-lead ECG during sinus rhythm exhibited biphasic and split P-wave with a prolonged duration, which called notched P-wave (NPW). Radio-frequency applica-tion in the coronary sinus (CS) resulted AF termination and elimination of triggering ectopy with NPW disappearance. The CS musculature which played a principal role in triggering and maintaining AF formed the NPW. In patients with repetitive recurrent AF after the estab-lishment of the PV isolation who exhibit NPW during sinus rhythm, the CS might be one of the arrhythmogenic sources of AF.