Objective : The efficacy and safety of the S-ICD system for the treatment of life-threatening ventricular arrhythmias have already been reported in large prospective studies. However, there are limited data on S-ICD use in Japan. We report our initial experience of S-ICD. Methods and Results : We analyzed 17 patients who underwent S-ICD（7）or transvenous-ICD（TV-ICD, 10）implantation at our institution from March 2016 to September 2016. In the S-ICD group, all patients were male, the mean age was 46.3±14.1 years, and the mean BMI（body mass index）was 23.3±2.6 kg/m². Four patients（57.1％） received S-ICD implantation for primary prevention while three（42.9％）received it for secondary prevention. Underlying cardiac diseases in the S-ICD group were ischemic cardiomyopathy（2）, nonischemic cardiomyopathy（2）and others（3）. Defibrillation testing was performed intraoperatively in all patients who received S-ICD. One of these patients had an initial conversion failure that required an additional procedure to reposition the system. Although no episode of in appropriate therapy was recorded group, two episodes of inappropriate shocks were recorded in the S-ICD group during the follow-up period. Conclusions : Initial experience of S-ICD at our institution seemed to be favorable. However, as the two episodes of inappropriate shocks due to oversensing of atrial flutter waves and noise were recorded, further studies are needed to optimize screening strategies, sensing vector and therapeutic zone.

Monophasic action potentials（MAPs）were demonstrated to show similar configurations to the action potentials recorded from myocardium by using glass microelectrode. MAP could then be recorded clinically by the development of suction electrode and contact electrode methods. In this review article, the history and principle of MAP and methods of MAP recording are described and an overview of basic research using MAP recordings in our laboratory is presented. The following topics are covered in this review : 1）Effects of regional hypoxia, hyperkalemia, and isoproterenol on left ventricular MAP duration, 2）Temporal changes in endocardial and epicardial MAP duration during acute myocardial ischemia（contribution of K_ATP channel） 3）Influence of short-term and long-term atrial fibrillation on atrial MAP, and 4）Characteristics of right ventricular MAP of drug-induced long QT syndrome and effects of K_ATP channel opener on right ventricular MAP.

Evaluation of the action potentials became possible clinically with establishiment of the technique of recording monophasic action potentials（MAPs）. There have been many clinical studies on MAP which provide novel insight on the pathogenesis of arrhythmias. In this review, an overview of the clinical studies involving MAP recordings conducted by the author and colleagues is presented. The following topics are covered in this review ; 1）Supernormal conduction of the intraventricular conduction，2）Right ventricular action potentials alternans，3）Contraction-excitation coupling of the atrial action potential duration，4）Effects of ATP on the right atrial action potentials，5）Local conduction block at the right atrium，6）Sinus node potential recording，7）Local atrial pacing capture during atrial fibrillation，8）Pseudo AV block in a patient with LQTS，9）Characteristics of the right atrial action potentials in patients with atrial fibrillation，10）Characteristics of myocardial action potentials in Brugadas syndrome，and 11）Effects of classⅢ antiarrhythmic drugs on the duration of atrial and ventricular action potential.