The progression of T waves is determined by non-propagating ventricular local repolarization. Although voltage-gated K⁺ channels play important roles in ventricular local repolarization, the exact pathophysiologic mechanisms of these channels have not been fully elucidated. To date, the alteration of T waves in various pathologic conditions has been discussed only empirically. In this review, we revisit changes in the ventricular repolarization process in various pathologic conditions such as drug-induced QT prolongation, cardiac memory, and heart failure. Moreover, we correlate these alterations with the dynamic equilibrium of channel density on the myocardial cell membrane. We believe that the control mechanisms for K⁺ channel dynamic equilibrium will bring about new knowledge to further establish the pathogenesis of multiple heart diseases.

Measurement of pacing impedance can be influenced by the implantable cardioverter-defibrillator and its leads, even when the case that the lead has not been changed. Some implantable cardioverter-defibrillators evaluate shock lead using low-voltage sub-threshold measurement of shock impedance, while others use the pacing impedance of the lead including the coil. Here, we describe a case in which the high impedance lead has been used since the first implantation of the defibrillator, followed by device exchange due to exhaustion of the generator battery two times. A total of three types of used defibrillators used different methods to measure lead impedance, resulting in different values. This case suggests that high pacing impedance values do not always indicate lead failure when the device model has been changed to one with a different impedance measurement method.

During catheterization of ventricular tachycardia, we have often found it difficult to identify the origin of ventricular tachycardia when tachycardia is not induced during the procedure or hemodynamics are disrupted. Late gadolinium enhancement（LGE）in cardiac MRI and late Iodine enhancement（LIE）in cardiac CT are reportedly performed to identify myocardial scar tissue and estimate the origin of ventricular tachycardia preoperatively. However, although LGE is useful for identifying the origin of tachycardia, the slice thickness is large and imaging takes a long time, and if a premature beat occurs or the device is inserted during imaging, a good image cannot be obtained. On the other hand, LIE also has poor resolution, making it difficult to take clear images. In this case report, the origin of ventricular tachycardia was presumed preoperatively using a new image processing method called Subtraction Myocardial Image for Late Iodine Enhancement（SMILIE）using a 320-row Area Detector CT, which was useful during catheter ablation.