Left bundle branch pacing（LBBP）has emerged as a new pacing technique that captures the intraventricular conduction system in patients with atrioventricular block（AVB）. A successful LBBP results in paced QRS duration comparable to His bundle pacing（HBP）while compensating for the disadvantage of HBP including a relatively high pacing threshold and difficulty in fixing the pacing lead. We performed LBBP in 30 AVB patients, in all of whom the procedure was successful. Paced QRS duration, pacing threshold, and ventricular potential amplitude were 128±15msec, 0.6±0.2V/0.4ms, and 11.0±7.2mV, respectively, and left bundle branch potential was recorded in 7 patients（23%）by the pacing electrode. No major complication was observed, and during a mean follow-up period of 6±3 months, any of lead dislocation, requirement of changing lead position or threshold increase >0.5V was observed. LBBP would be useful not only in preventing pacemaker-induced cardiomyopathy but in achieving electrical resynchronization for LBBB.

Long QT syndrome is a lethal arrhythmic disorder caused by mutations in genes encoding ion channels and related proteins. Recent advances in genome analysis technologies have raised the issue of interpreting genetic variants of unknown significance. Since human induced pluripotent stem（iPS）cell models mimic the phenotypes of diseases, they may play an important role in solving problems associated with genotype-phenotype mismatch. We have shown that disease-specific iPS cell-derived cardiomyocytes（iPSC-CMs）differentially respond to specific ion-channel blockers, reflecting ion channel abnormalities. These results indicate that this strategy may enable us to detect abnormal channels based on the phenotype of patient-specific iPSC-CMs. This method may also be useful in diagnosing cases where pathogenic genetic mutations cannot be identified. In addition, iPSC-CMs are being studied as an experimental model for the development of therapies for hereditary arrhythmias. Here, we discuss the latest iPSC technologies related to hereditary arrhythmias.

To prospectively investigate the timing and factors associated with the occurrence of atrial fibrillation（AF）in hemodialysis（HD）, we studied 24 HD patients with cardiac implantable electrical devices（male : n＝16, mean age : 74±10 years, Pacemaker : n＝18, Implantable cardioverter defibrillator : n＝3, Cardiac resynchronization therapy defibrillator : n＝3）. We analyzed the occurrence-timing and burden of AF from device-stored data during a mean follow-up period of 9±1 months. Sixteen patients（67％）had at least one AF event. Furthermore, AF events per hour were significantly more frequent during HD than during the other periods without HD（p＜0.01）. The AF burden per hour was significantly higher during HD and from 24 hours before HD to the start of HD than at the other times（p＜0.05）. Patients with AF during HD had significantly lower serum potassium levels than those without AF（4.4±0.2mEq/L vs 4.7±0.2mEq/L, p＝0.01）. The incidence of AF during HD was higher, and low serum potassium level was associated with AF occurrence in HD patients.