A conventional two-dimensional cell sheet of human induced pluripotent stem cell-derived cardiomyocytes lying on microelectrode array probes has been employed to estimate their excitation-conduction properties. By applying local electric stimuli on the cell sheet, the proarrhythmic and antiarrhythmic profiles of a drug can be systematically evaluated. Drug-induced changes in contraction-relaxation motion can also be evaluated using the cell sheet. Namely, a physiological property called “positive contraction velocity-frequency relationship” can be developed in the cell sheet by initiating the excitation, contraction, and relaxation in the same area. In order to fully elicit the contractile motion of the cell sheet, it is essential to set the stimulation sites around the maximum relaxation region to overcome its physical limitation due to lying on the plastic probe ; i.e., the center of the cell sheet is stretched toward its peripheral area. This finding may suggest that cardiac resynchronization therapy can be further improved by adopting the currently described new concept of cardiac pacing with monitoring of ventricular motion.

The gold standard treatment for bradyarrhythmia is the implantation of an artificial permanent pacemaker. However, complications such as infection and exacerbation of heart failure due to unphysiological pacing can occur, so the development of novel therapeutic strategies for bradyarrhythmias has been warranted. Research on gene therapy and cell therapy for bradyarrhythmia is ongoing. The methods to increase the automaticity of the working myocardium by regulating ion channels and transforming cells into those with pacemaker function, and to produce ectopic excitation comparable to junctional rhythm by transplanting stem cell-derived beating cells into the left ventricle have been reported. While the development of biopacemakers is advancing, there are few reports to date on the repair of atrioventricular conduction defects caused by atrioventricular block, and there is no established electrophysiological characterization of such defects. We therefore established an in vitro cell transplantation evaluation platform using iPS cell-derived cardiomyocytes derived from the same animal species as the living myocytes and explored the possibility of regenerative therapy for cardiac conduction defects. Here we report the results of our study and a review of the literature regarding previously reported gene and cell therapies for bradyarrhythmias.

Previously we have manually described the CV with non-contrast computed tomography but it is often difficult to describe the CV branches. So we invented a new method（Fat description method）that is able to analyze the CV anatomy focusing on the relationship between the CV and the epicardial fat（Fat）and is able to describe the CV branches. The aim of this study is to evaluate the accuracy of this method. In a total of 52 patients implanted with CRT devices, we describe the main CV with non-contrast computed tomography and the CV branches with the Fat description method. The described CV branches were classified as anterior, lateral, and posterior, and accuracy was evaluated in 3 grades （1 : exactly described ; 2 : partly described ; 3 : not described）compared to the CV venogram during the implantation. The target CV branches were 70 veins : 21 veins in the anterior site, 26 veins in the lateral site, and 23 veins in the posterior site. In the anterior site 8 veins were grade 1（38.1％）, 5 veins were grade 2（23.8％）, and 8 veins were grade 3（38.1％）. In the lateral site, 14 veins were grade 1（53.8％）, 4 veins were grade 2（15.4％）, and 8 veins were grade 3（30.8％）. In the posterior site, 15 veins were grade 1（65.2％）, 6 veins were grade 2（8.7％）, and 2 veins were grade 3（8.7％）. Fat description is an exact and effective method to describe the CV branches but depends on the presence of fat.

The mechanism of AF ablation-related atrial tachycardias（ATs）is macro-reentry, and these ATs frequently rotate around anatomical obstacles such as pulmonary veins, tricuspid valve, and mitral valve. A linear ablation between these anatomical obstacles is therefore an important strategy to treat them. Differential pacing is normally used to confirm the achievement of linear lesion at the cavo-tricuspid isthmus, but this concept has also been applied to assess the achievement of the other linear lesions. However, high-resolution mapping demonstrates that pseudo-block is observed in 20-30％ of cases. Novel omnipolar technology selects an optimal local EGM from omnipolar EGMs in 360 degrees calculated from cliques, composed of 3 unipoles and 2 orthogonal bipoles, displaying them as Activation Vectors. We demonstrate a case in which the achievement of linear lesions was successfully diagnosed in real time by this function.