Introduction: His bundle pacing (HBP) was developed as a physiological conduction system pacing to complement the problem of conventional right ventricular pacing (RVP) related to dyssynchrony. Recently, left bundle branch area pacing (LBBAP), which overcomes the shortcomings of HBP, has been implemented. Most researches on initial experiences with LBBAP have reported that it was achieved through a lumen-less pacing lead (LLL) with a fixed helix design; however, there are situations in which LLL cannot be used. The purpose of present research is to evaluate the initial experience and learning curve of LBBAP using a standard stylet-driven lead with an extendable helix design. Methods: 265 patients who underwent LBBAP or conventional RVP performed by operators without previous LBBAP experience at Yonsei University Severance Hospital in Korea between December 2020 and October 2021 were enrolled. LBBAP was performed using a stylet‐driven pacing lead with an extendable helix. The learning curve was evaluated by analyzing fluoroscopy and procedure times. Results: LBBAP was successful in 65 of 69 (94.2%) patients during the observation period. In 65 patients who underwent LBBAP, mean fluoroscopy and procedural times were 17.1 ± 17.2 minutes and 64.2 ± 33.5 minutes, respectively. The learning curve for achieving LBBAP plateaued after the 24th case, with a gradually shortened in procedure time. Conclusion: During the initial experience with LBBAP, fluoroscopy and procedural times improved with increasing operator experience. For operators who were experienced in cardiac pacemaker implantation, the steepest part of the learning curve was over the first 20-25 cases.

Background: Sinoatrial node dysfunction and atrial fibrillation (AF) frequently coexist and interact with each other, often to initiate and perpetuate each other. Objective: To determine the effect of AF on the incidence and risk of sick sinus syndrome (SSS). Methods: The association of incident AF with the development of incident SSS was assessed from 2004 to 2013 in 302,229 SSS- and pacemaker-free participants aged ≥60 years in the Korea National Health Insurance Service-Senior cohort. Results: During an observation period of 1,854,800 person-years, incident AF was observed in a total of 12,797 participants (0.69%/year). The incidence of SSS was 0.2 and 3.4 per 1000 person-years in the incident AF and the propensity score matched no-AF groups, respectively. After adjustment, the risk of SSS caused by incident AF was significantly increased, with a hazard ratio (HR) of 13.4 (95% confidence interval [CI]: 8.4–21.4). This finding was consistently observed after censoring for heart failure (HR, 16.0; 95% CI: 9.2–28.0) or heart failure/myocardial infarction (HR, 16.6; 95% CI: 9.3-29.7). Incident AF also was associated with an increased risk of pacemaker implantation related with both SSS (HR, 21.8; 95% CI: 8.7–18.4) and atrioventricular (AV) block (HR, 9.5; 95% CI: 4.9–18.4). These results were consistent regardless of sex and comorbidities. Conclusion: Incident AF was associated with more than ten times increased risk of SSS in an elderly population regardless of comorbidities. Risk of pacemaker implantations related with both sinus node dysfunction and AV block were increased in elderly population with incident AF.

Introduction: Short QT syndrome is a rare, inherited channelopathy associated with sudden cardiac arrest (SCA) but characteristics and prognosis of short QT interval (SQTI) in Asian patients remain unclear. This study aimed to determine clinical characteristics of and outcomes in patients with SQTI in an Asian population. Methods: Consecutive patients with SQTI were recruited. SQTI was defined as a Bazett’s formula-corrected QT interval (QTc) ≤340 ms in serial electrocardiograms. Age- and sex-matched patients with a normal QTc and without overt cardiovascular disease were included at a 1:4 ratio. Clinical and ECG features and outcomes were compared between patients with and without SQTI. Results: Thirty-four patients with SQTI [age, 23.5 (21–30.5) years; 31 male] were followed up for 4.8 (2.0–7.8) years. Early repolarization, tall T wave, and U wave were significantly more frequent in patients with SQTI than the patients without SQTI. QT dispersion [44.0 (28.0–73.0) vs. 20.0 (12.0–35.0) ms, P<0.001] was significantly wider and heart rate [52.0 (47.0–58.0) vs. 70.0 (62.3–84.0) /min, P<0.001] was significantly slower in patients with SQTI than patients without SQTI. Atrial fibrillation (AF, 11.8% vs. 2.2%, P=0.030) and ventricular arrhythmia (VA)/SCA (8.7% vs 0%, P=0.007) were significantly more frequent in patients with SQTI than patients without SQTI. SQTI was significantly associated with AF [odds ratio, 5.911; 95% confidence interval, 1.257–27.808; P=0.025] and VA/SCA. Conclusions: In this Asian population, SQTI was associated with AF and VA/SCA.