Background The clinical course and therapeutic strategies in the congenital long QT syndrome (LQTS) are genotype-specific. However, accurate estimation of LQTS-genotype is often difficult from the standard 12-lead ECG. Objectives This study aims to evaluate the utility of QT/RR slope analysis by the 24-hour Holter monitoring for differential diagnosis of LQTS-genotype between LQT1 and LQT2. Methods This cross-sectional study enrolled 54 genetically identified LQTS patients (29 LQT1 and 25 LQT2) recruited from 3 medical institutions. The QT-apex (QTa) interval and the QT-end (QTe) interval at each 15-second were plotted against the R-R intervals and the linear regression (QTa/RR and QTe/RR slopes, respectively) were calculated from the entire 24-hour and separately during the day or night-time periods of the Holter recordings. Results The QTe/RR and QTa/RR slopes at the entire 24-hour were significantly steeper in LQT2 compared to those in LQT1 patients (0.262 +/- 0.063 vs 0.204 +/- 0.055, P = 0.0007; 0.233 +/- 0.052 vs 0.181 +/- 0.040, P = 0.0002, respectively). The QTe interval was significantly longer, QTe/RR and QTa/RR slopes at daytime were significantly steeper in LQT2 than in LQT1 patients. The receiver operating curve analysis revealed that the QTa/RR slope of 0.211 at the entire 24-hour Holter was the best cut-off value for differential diagnosis between LQT1 and LQT2 (sensitivity: 80.0%, specificity: 75.0% and area under curve: 0.804 [95%CI = 0.68-0.93]). Conclusion The continuous 24-hour QT/RR analysis using the Holter monitoring may be useful to predict the genotype of congenital LQTS, particularly for LQT1 and LQT2.

We describe our use of intracardiac echocardiography (ICE) to guide endomyocardial biopsy of the left ventricle in a patient with chronic heart failure secondary to endocardial fibroelastosis. Under ICE guidance, we advanced the bioptome through the middle of the mitral annulus, within a trans-septal sheath, and guided the bioptome to the correct location on the mid-posterior wall of the left ventricle. This was performed without adverse events, such as injury to the chordae tendineae or mitral valve regurgitation. Therefore, ICE-guidance is possible for left-sided heart procedures and could lower the risk of complications and improve the biopsy rate for diagnosis.

Introduction: There are few reports of the characteristics, mechanisms, and outcomes of atrial tachycardia (AT) and atrial fibrillation (AF) ablation after cardiac surgery and concomitant Maze procedures. This study investigated the mechanisms and long-term outcomes of AT and AF ablation after various Maze procedures, especially we examined in detail whether the arrhythmia after Maze procedure was due to gap or not. Methods and Results: We analyzed 37 consecutive cases with AT and AF after cardiac surgery and Maze procedure between 2007 and 2019. Fifty-nine atrial arrythmias were induced in 37 consecutive cases, and 49 of those atrial arrythmias were mappable ATs. Forty-two ATs was related to the Maze procedure in the 49 mappable ATs (87.5%). All 37 consecutive cases had residual electrical conductions (gaps) in the Maze lines (88 gaps; 2.4±1.2 gaps/patient). Forty-two of 88 gaps (47.7%) were associated with gap-related ATs. The most common gap-related ATs in this study were peri-mitral atrial flutter in 22 cases. The median follow-up period after ablation was 3.6±3.2 years (median, 2.1 years; interquartile range, 0.89-6.84). The Kaplan-Meier analysis of freedom from recurrent atrial arrhythmia after Maze procedure was 79.9% at 1-year follow up and 69.3% at 4-year follow up. Conclusions: Reentry was the main mechanism of AT after cardiac surgery and concomitant various Maze procedures, and AT were largely related to the gap in the Maze line between mitral valve anulus and pulmonary vein isolation line. Catheter ablation of AT after various Maze procedures seemed to be effective and safe during long-term follow-up.