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Abstract Introduction After mitral isthmus (ΜΙ) catheter ablation, perimitral atrial flutter (PMF) circuits can be maintained due to the preservation of residual myocardial connections, even if conventional pacing criteria for complete MI block are apparently met (MI pseudo‐block). We aimed to study the incidence, the electrophysiological characteristics, and the long‐term outcome of these patients. Methods Seventy‐two consecutive patients (mean age 62.4 ± 10.2, 62.5% male) underwent MI ablation, either as part of an atrial fibrillation (AF) ablation strategy (n = 35), or to treat clinical reentrant atrial tachycardia (AT) (n = 32), or to treat AT that occurred during ablation for AF (n = 5). Ιn all patients, the electrophysiological characteristics of PMF circuits were studied by high‐density mapping. Results Mitral isthmus block was successfully achieved in 69/72 patients (95.6%). Five patients developed PMF after confirming MI block. In these patients, high‐density mapping during the PMF showed a breakthrough in MI with extremely low impulse conduction velocity (CV). In contrast, in usual PMF circuits that occurred after AF ablation, the lowest CV of the reentrant circuit was of significantly higher value (0.07 ± 0.02 m/s vs 0.25 ± 0.07 m/s, respectively; P

Introduction: After mitral isthmus (ΜΙ) catheter ablation, perimitral atrial flutter (PMF) circuits can be maintained due to the preservation of residual myocardial connections, even if conventional pacing criteria for complete MI block are apparently met (MI pseudo‐block). We aimed to study the incidence, the electrophysiological characteristics, and the long‐term outcome of these patients. Methods: Seventy‐two consecutive patients (mean age 62.4 ± 10.2, 62.5% male) underwent MI ablation, either as part of an atrial fibrillation (AF) ablation strategy (n = 35), or to treat clinical reentrant atrial tachycardia (AT) (n = 32), or to treat AT that occurred during ablation for AF (n = 5). Ιn all patients, the electrophysiological characteristics of PMF circuits were studied by high‐density mapping. Results: Mitral isthmus block was successfully achieved in 69/72 patients (95.6%). Five patients developed PMF after confirming MI block. In these patients, high‐density mapping during the PMF showed a breakthrough in MI with extremely low impulse conduction velocity (CV). In contrast, in usual PMF circuits that occurred after AF ablation, the lowest CV of the reentrant circuit was of significantly higher value (0.07 ± 0.02 m/s vs 0.25 ± 0.07 m/s, respectively; P <.001). Patients presented with clinical AT had better prognosis in maintaining sinus rhythm after MI ablation compared with patients presented with AF. Conclusion: Perimitral atrial flutter with MI pseudo‐block may be present after MI ablation and has specific electrophysiological features characterized by remarkably slow CV in the MI. Thus, even after MI block is achieved, a more detailed mapping in the boundaries of the ablation line or reinduction attempts may be needed to exclude residual conduction. [ABSTRACT FROM AUTHOR]

Objective: In this study, we describe our experience utilising Advisor™ High Density (HD) Grid mapping catheter in transcatheter ablation of intraatrial re-entrant and focal atrial tachycardias with or without CHD., Methods: Forty-five consecutive patients with intraatrial re-entrant and focal atrial tachycardia who underwent a transcatheter ablation procedure by using Advisor™ HD Grid mapping catheter and high-density mapping system in our hospital from January 2017 to January 2023 were included into the study., Results: The mean age of the patients was 14.2 ± 7.3 years (6-32 years), and the mean weight was 48.3 ± 16.2 kg (22-83 kg). Of the total 45 patients, 21 were intraatrial re-entrant tachycardia and 25 were focal atrial tachycardia. Of the 21 re-entrant circuits, 15 were classified as cavotricuspid isthmus-dependent and 5 were non-cavotricuspid isthmus-dependent. In one patient, two re-entrant circuits were identified. A transbaffle ablation was successfully performed from the left atrium in one patient. Of the 25 focal atrial tachycardia, 19 were from right atrium and 6 were from left atrium. A cryoablation was performed in only one patient and radiofrequency ablation in others. The mean procedure time was 180 ± 64 minutes. The mean follow-up period was 69.3 ± 35.3 months. Acute success was 95.5%. Recurrence was noted in two patients (4.4%)., Conclusion: Advisor™ HD Grid mapping catheter was found to be safe and achieved an acceptable success in transcatheter ablation of patients with intraatrial re-entrant tachycardia and focal atrial tachycardias.

Following atrial fibrillation (AF) ablation procedures, patients may present with atrial tachycardias (ATs) that show remarkable stability for short periods of time but degenerate in unstable forms right afterwards. In order to map these types of ATs, we applied the sequential mapping capabilities only for time segments where ATs exhibited constant cycle length (CL) and activation sequence, excluding the segments with unstable recordings. We herein describe two cases of ATs after AF ablation which were mapped with this technique that allowed for the successful identification and subsequent ablation of the tachycardia circuit. [ABSTRACT FROM AUTHOR]

Supraventricular arrhythmias are often observed in patients before and after atrial septal defect repair. Although several papers report different incidences of sustained supraventricular arrhythmias, postoperative ‘incisional’ macrore-entrant tachycardias have not been systematically investigated.Methods We reviewed 136 consecutive patients (79 female, 57 male, mean age 36·8±17·8 years) who underwent atrial septal defect repair at our institutions between January 1990 and January 1999. Coexisting valve disease requiring surgical intervention was noted in 13 patients (9·5%). The mean follow-up period was 78·8±30·1 months. Results Sustained supraventricular arrhythmias occurred in 12 patients (8·8%) before surgery (atrial fibrillation in 11 patients). Using multivariate analysis the occurrence of arrhythmia significantly correlated with the presence of coexisting heart disease (P< 0·001) and age at surgery (P=0·011) After surgery sustained supraventricular arrhythmias were recorded in 16 patients (11·7%). Eleven of them had atrial fibrillation, permanent in 8 cases, 4 ‘incisional’ macroreentrant atrial tachycardia and 1 atrioventricular re-entry tachycardia. There was a significant correlation between pre and postoperative arrhythmia (P< 0·001). Two of the 4 patients with macroreentrant atrial tachycardia underwent successful radiofrequency catheter ablation, whereas the arrhythmia was controlled medically in the remaining 2 patients. Conclusions Atrial fibrillation remains the most frequent form of arrhythmia before and after surgical closure of atrial septal defects in adulthood, and relates to age at the time of repair and coexisting heart disease. Incisional macroreentrant atrial tachycardia is an identifiable, albeit less common, form of tachycardia, which can be treated by transcatheter ablation. [ABSTRACT FROM PUBLISHER]

Prerequisite for succesful radiofrequency catheter ablation of tachycardias is the exact mapping during the electrophysiological study. The new mapping system CARTO allows a three-dimensional color-coded electroanatomic map of impulse propagation using electromagnetic technology. The aim of this study was to determine the feasibility and safety of the new electromagnetic mapping technology CARTO for atrial tachycardias. Results: Electrophysiologic study and CARTO mapping was performed in 38 atrial tachycardias. The mapping procedure took 26 ± 23 min. We created 33 maps within the right atrium and 5 maps within the left atrium with a mean of 74 ± 38 different catheter positions. The mechanism was determined as reentrant in 9, junctional in 1 and focal in 28 tachycardias. In focal tachycardias the tachycardia cycle length (CL) and the total atrial activation time (AT) were clearly different (352 ± 98 ms vs 99 ± 25 ms). Reentrant tachycardias had a comparable CL and AT (236 ± 44 ms vs 240 ± 56 ms). In 83% of the focal tachycardias and in 67% of the reentrant tachycardias, ablation was performed successfully. No complications occured. Conclusion: The electroanatomic mapping system allows high resolution visualization of electrical activity and may therefore improve precision and simplify the determination of the arrhythmogenic substrate during tachycardias for successful catheter ablation. [ABSTRACT FROM AUTHOR]

Animal models of atrial flutter and early mapping studies of human atrial flutter have .suggested the importance of barriers in this reentrant arrhythmia. The consistency of rate and morphology of typical atrial flutter suggest a common anatomic substrate for this arrhythmia. The unique endocardial architecture of the right atrium provides anatomic barriers around which reentry occurs. In typical human atrial flutter, the crista terminalis, eustachian ridge, and tricuspid annulus have been identified as barriers to conduction. The importance of conduction barriers, methodology for defining barriers, the anatomic substrate for these harriers, and the role of these barriers in other atrial arrhythmias are discussed. [ABSTRACT FROM AUTHOR]