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Background:The displacement of cardiac implantable electronic devices (CIEDs) toward the caudal side during standing after CIED implantation could cause lead dislodgement. This study investigated the relationship between supine pocket position and standing CIEDs' displacement distance after the implantation. Methods:After CIED surgeries performed at 2 hospitals between 2012 and 2020, 134 patients underwent postoperative chest x-rays in the supine and standing positions during hospitalization. To measure the displacement distance of CIEDs from the supine to the standing position, we identified the first thoracic vertebrae (Th1) in the supine position using the first rib as an index, drew a horizontal line at the lower edge of the Th1, and calculated the distance from that point to the upper edge of the CIED. The difference between measures for the two positions was compared. At the position of the pocket in the thorax in the supine position, the ratio of the distance between the thorax and the device is defined as the device thorax ratio (DTR). We examined the relationship between DTR and CIED displacement distance. Results:In this study, we included 134 patients (53% men; median age, 79 years, body mass index, 22.3 ± 3.4; pacemaker 93%, left implantation 96%). We found that the more lateral the position of the CIED pocket, the more the CIED fell when standing (confidence interval = 0.34-0.60, P < .001). Conclusions:The farther the CIED was implanted outside the thorax in the supine position, the more significantly the CIED was displaced in the standing position.

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Background An implantable cardioverter defibrillator (ICD) is the most reliable therapeutic device for preventing sudden cardiac death in patients with sustained ventricular tachycardia (VT). Regarding its effectiveness, targeted VT is defined based on the tachyarrhythmia cycle length. However, variations in RR interval variability of VTs may occur. Few studies have reported on VT characteristics and effects of ICD therapy according to the RR interval variability. We aimed to identify the clinical characteristics of VTs and ICD therapy effects according to the RR interval variability. Methods We analyzed 821 VT episodes in 69 patients with ICDs or cardiac resynchronization therapy defibrillators. VTs were classified as irregular when the difference between two successive beats was >20 ms in at least one of 10 RR intervals; otherwise, they were classified as regular. We evaluated successful termination using anti‐tachycardia pacing (ATP)/shock therapy, spontaneous termination, and acceleration between regular and irregular VTs. The RR interval variability reproducibility rates were evaluated. Results Regular VT was significantly more successfully terminated than irregular VT by ATP. No significant difference was found in shock therapy or VT acceleration between the regular and irregular VTs. Spontaneous termination occurred significantly more often in irregular than in regular VT cases. The reproducibility rates of RR interval variability in each episode and in all episodes were 89% and 73%, respectively. Conclusions ATP therapy showed greater effectiveness for regular than for irregular VT. Spontaneous termination was more common in irregular than in regular VT. RR interval variability of VTs seems to be reproducible.