Narrow QRS ectopy with concealed connections from a para-Hisian origin to the proximal left fascicles.

INTRODUCTION: Catheter ablation of ectopy originating from the vicinity of the His bundle can be challenging. METHODS AND RESULTS: We report a case of a 33-year-old man with narrow QRS ectopy with preferential conduction from a para-Hisian origin to the proximal left fascicles, which was successfully eliminated by radiofrequency ablation in the right coronary cusp, guided by ultrahigh-resolution mapping of the His bundle, bundle branch, and fascicular electrograms. CONCLUSION: Some narrow QRS ectopy may originate from the vicinity of the conduction system, instead of the "true" conduction system, and have concealed connections from its origin to the conduction system.

Complete free wall isolation of arrhythmogenic persistent left superior vena cava.

INTRODUCTION: Persistent left superior vena cava (PLSVC) is one of the major sources of triggers and drivers of atrial fibrillation (AF). There has been no established PLSVC ablation procedure to eliminate the arrhythmogenicity along the entire length of PLSVC. METHODS AND RESULTS: A 70-year-old woman with a history of two previous catheter ablations for AF, mitral valvuloplasty, and an unroofed coronary sinus-type atrial septal defect closure underwent the redo AF ablations. The AF trigger and driver were identified within the patient's enlarged PLSVC. The AF was treated by complete PLSVC free wall isolation. CONCLUSION: Complete PLSVC free wall isolation may be an effective ablation method to eliminate the arrhythmogenicity along the entire length of the PLSVC.

Quantitative analysis of fractionated electrogram area of left atrium during right atrial pacing as an indicator of left atrial electrical remodeling in patients with atrial fibrillation.

Background: The clinical significance of left atrial local electrogram fractionation after restoration of sinus rhythm in patients with atrial fibrillation (AF) has not been elucidated. Methods: We evaluated ultrahigh-resolution maps of the left atrium (LA) during RA pacing acquired after pulmonary vein isolation in 40 patients with AF. The association between low-voltage area (LVA, <0.5 mV), fractionated electrogram area (FEA, the highlighted area with LUMIPOINT™ Complex Activation), the interval from onset of LA activation to wavefront collision at the mitral isthmus (LA activation time), and wave propagation velocity (WPV) was evaluated quantitatively. Results: The total LVA, total FEA with ≥5.0 peaks or ≥7.0 peaks were 7.0 ± 7.9 cm2, 15.9 ± 12.9 cm2, and 5.2 ± 7.5 cm2, respectively. These areas were predominantly observed in the anteroseptal region. Total LVA, total FEA with ≥5.0 peaks, and total FEA with ≥5.0 peaks in the normal voltage area (NVA: ≥0.5 mV) correlated with LA activation time (R = 0.69, 0.75, and 0.71; each p < .0001). In the anterior wall, these areas correlated with regional mean WPV (R = -0.75, -0.83, and - 0.55; each p < .0001) and the extent of slow conduction area (SCA) with WPV <0.3 m/s (R = 0.89, 0.84, 0.33; p < .0001 for LVA and FEA, p < .05 for FEA located in NVA). The anterior wall FEA with ≥7.0 peaks and that in the NVA showed a better correlation in predicting anterior wall SCA (R = 0.92 and 0.86, each p < .0001). Conclusion: Quantitative analysis of FEA together with LVA may facilitate the assessment of LA electrical remodeling.

Evaluation of interatrial conduction pattern after pulmonary vein isolation using an ultrahigh-resolution electroanatomical mapping system.

Interatrial conduction consists of various muscular bundles, including the Bachmann bundle. In this study, we investigated interatrial activation patterns using ultrahigh-resolution left atrial endocardial mapping. This study investigated 58 patients who underwent catheter ablation of atrial arrhythmia via an ultrahigh-resolution mapping system (Rhythmia) at our hospital from May 2020 to January 2021. Left atrial voltage maps and activation maps were acquired after the ablation procedure during right atrial appendage (RAA) pacing. We defined left atrial breakout sites (LABSs) as centrifugal activation patterns shown by the LUMIPOINT Activation Search Tool. The distance between each LABS in the left atrial anterior wall and the superior border of the interatrial septum (DLABS-IAS) was measured on the shell of the electroanatomical map, and anterior LABSs were divided equally into roof- and septal-side groups. Fifty-three (91%) patients underwent cryoballoon pulmonary vein isolation. Ultrahigh-resolution left atrial mapping was successfully performed in all patients (6831 ± 2158 points). A total of 82 LABSs were identified in left atrial anterior wall; 34 patients had single LABS and 24 patients had dual LABSs. The mean DLABS-IAS was 10.3 ± 9.6 mm. Seven patients also exhibited posterior LABS near the interatrial raphe below the right inferior pulmonary vein. Patients with a single roof-side LABS had significantly shorter left atrial activation times than those with a single septal-side LABS (81.6 ± 13.2 ms vs. 93.5 ± 13.7 ms, p < 0.05). Interatrial conduction patterns during RAA pacing varied between patients and affected the left atrial activation time.

Perimitral atrial tachycardias dependent on residual nonligament of Marshall conduction.

INTRODUCTION: Catheter ablation for perimitral atrial tachycardia (PMAT) that persists despite lateral mitral isthmus (LMI) ablation is challenging. The aim of this study was to identify the role of the ligament of Marshall (LOM) in PMATs that persist after LMI conduction block has been created, and evaluate the validity of ethanol infusion into the vein of Marshall (VOM) as treatment. METHODS AND RESULTS: Sixteen consecutive PMATs in 13 patients that persisted despite apparent LMI conduction block, which was confirmed by ultrahigh-resolution mapping and entrainment pacing along the mitral annulus, were analyzed. PMATs were classified into two types based on the location of the endocardial breakthrough site: those utilizing the LOM (n = 13), which had a breakthrough site along with the LOM, and those not utilizing the LOM (n = 3), which had a breakthrough site at an anterior or posterior side of the LOM. Of the 16 PMATs, 5 PMATs (31%) were not suitable for ethanol infusion into the VOM because the LOM was not involved in the tachycardia circuit or because of the anatomy of the VOM. Fourteen PMATs (88%) were successfully terminated solely by breakthrough site ablation. At a mean follow-up period of 12 ± 9 months, 10 (77%) patients have remained free from atrial tachyarrhythmias. CONCLUSION: In cases of PMAT following LMI ablation, epicardial conduction over the LMI can occur independently of the LOM. Ethanol infusion into the VOM in such cases would not abolish residual epicardial conduction. The anatomy of the VOM can also preclude the use of this method.

The mechanisms of left septal and anterior wall reentrant atrial tachycardias analyzed with ultrahigh resolution mapping: The role of functional block in the circuit.

BACKGROUND: Low voltage areas (LVAs) are most commonly observed on the left atrial (LA) septal/anterior wall. OBJECTIVE: We explored the mechanisms of LA septal/anterior wall reentrant tachycardias (LASARTs) using ultrahigh resolution mapping. METHODS: This study included seven consecutive LASARTs in six patients (75 [62.2-82.8] years, 4 women) who underwent atrial tachycardia (AT) mapping and ablation using Rhythmia systems. RESULTS: The AT cycle length was 266 (239-321) ms. During ATs, 11.0 (9.0-12.9) cm2 of LVAs were identified in all, and 0.8 (0.7-1.7) cm2 of dense scar was identified in four patients. Five ATs rotated around dense scar, while two rotated around functional linear block, which was confirmed during atrial pacing after AT termination. The AT circuit length was 8.7 ± 2.1 cm with a conduction velocity of 30.4 ± 3.7 cm/s. A median of 3.0 (2.0-4.0) slow conduction areas per circuit were identified, and 17/23 (73.9%) areas were present in LVAs, while they were at the border of the LVA and normal voltage areas in the remaining 6/23 (26.1%). Global activation histograms facilitated the identification of the critical isthmus in all. Tailor-made ablation at critical isthmuses successfully eliminated all ATs. However, one patient with AT related to functional linear block experienced recurrent AT related to dense scar, which progressed after the procedure. During a mean 14 ± 13 month follow-up after the last procedure, no patients experienced recurrent ATs without any complications. CONCLUSION: LASARTs consist of not only fixed conduction blocks but also functional conduction blocks. Ultrahigh resolution mapping is highly useful to decide the optimal tailor-made ablation strategy based on the mechanisms.

Ultrahigh resolution electroanatomical mapping of the transverse conduction of the right atrial posterior wall in cases with and without typical atrial flutter.

INTRODUCTION: The right atrial posterior wall (RAPW) is known to form a conduction barrier during typical atrial flutter (AFL). We evaluated the transverse conduction properties of RAPW in patients with and without typical AFL using an ultrahigh resolution electroanatomical mapping system. METHODS AND RESULTS: This study included 41 patients who underwent catheter ablation of AF, typical or atypical AFL, in whom we performed RAPW mapping with an ultrahigh resolution mapping system during typical AFL and coronary sinus ostial pacing with three different pacing cycle lengths (PCLs) (1) PCL1: PCL within 40 ms of the AFL cycle length in patients with typical AFL or 250-300 ms for those without, (2) PCL2: 400 ms, (3) PCL3: PCL just faster than the sinus rate. Local RAPW conduction block was evaluated by propagation mapping and local double potentials separated by an isoelectric line. The functional block was defined as areas blocked during shorter PCLs but conductive during longer PCLs. The degree of blockade was calculated by dividing the blocked length by RAPW length (%blockade). Only two patients demonstrated a fixed complete RAPW block (100%, %blockade). Thirty-one patients demonstrated a partial block of RAPW, and the %blockade during PCL1-3 was 49.4 ± 19.8%, 39.5 ± 19.2%, and 35.0 ± 22.9% in this group, respectively. Functional block areas were frequently observed above the fixed block area adjacent to the RA-inferior vena cava junction. Transverse conduction block was more frequently observed in patients with typical AFL at any longitudinal level of RAPW. CONCLUSION: RAPW transverse conduction block is lower-side dominant and greater in patients with typical AFL than those without.

Epicardial-endocardial breakthrough site ablation: Demonstration of alternative target for perimitral atrial tachycardia.

A 62-year-old man underwent the catheter ablation for persistent atrial tachycardia (AT) with a cycle length of 357 milliseconds. An ultrahigh resolution mapping revealed that this tachycardia was a clockwise perimitral AT despite the conduction was apparently blocked across the lateral mitral isthmus line both at the endocardium and within the coronary sinus. The AT was terminated by the single radiofrequency application at the site below the mitral isthmus line where the endocardial activation breakout was seen. This case suggests that the epicardial-endocardial conduction breakthrough site may be an alternative ablation target in a difficult ablation case of perimitral AT.

Characteristics of Single-Loop Macroreentrant Biatrial Tachycardia Diagnosed by Ultrahigh-Resolution Mapping System.

BACKGROUND: Biatrial tachycardia (BiAT) is a rare form of atrial macroreentrant tachycardia, in which both atria form a critical part of the circuit. We aimed to identify the characteristics and precise circuits of single-loop macroreentrant BiATs. METHODS AND RESULTS: We identified 8 patients (median age, 59.5 years old) with 9 BiATs in a cohort of 336 consecutive patients from 2 institutions who had undergone AT catheter ablation using an automatic ultrahigh-resolution mapping system. Seven of the 8 patients had a history of persistent AF ablation, including septal or anterior left atrium ablation before developing BiAT. One of the 8 patients had a history of an atrial septal patch closure with a massively enlarged right atrium. Nine ATs (median cycle length, 334 ms; median 12 561 points in the left atrium; 8814 points in the right atrium) were diagnosed as single-loop macroreentrant BiATs. We observed 3 types of BiAT (1) BiAT with a perimitral and peritricuspid reentrant circuit (n=3), (2) BiAT using the right atrium septum and a perimitral circuit (n=3), and (3) BiAT using only the left atrium and right atrium septum (n=3). Catheter ablation successfully terminated 8 of the 9 BiATs. CONCLUSIONS: All patients who developed BiAT had an electric obstacle on the anteroseptal left atrium, primarily from prior ablation lesions. In this situation, mapping of both atria should be considered during AT. Because 3 types of single-loop BiAT were observed, ablation strategies should be adjusted to the type of BiAT circuit.