Idiopathic Atypical Atrial Flutter Is Associated With a Distinct Atriopathy

Ultra High-Density Mapping and Ablation of Localized Micro-Reentrant Tachycardias: Insight From the CHARISMA Registry

BACKGROUND

Recent advancements in ultra-high-density mapping (UHDM) featuring automated functionalities have enhanced our understanding of micro-reentrant atrial tachycardias (mAT) circuits and the precise localization of the origin.

PURPOSE

To evaluate the diagnostic support provided by an automated UHDM algorithm in guiding the ablation of mATs.

METHODS

Consecutive patients eligible for AT ablation in 22 Italian centers were prospectively enrolled. All ATs were comprehensively mapped in either the left or right atrium utilizing the RHYTHMIA mapping system. The LUMIPOINT tool was systematically employed to confirm electrogram fragmentation within this defined area.

RESULTS

Among 159 ATs analyzed, 97 (61.0%) were identified as macro-reentrant ATs, 50 (31.4%) as focal ATs and 12 (7.5%) as mATs. Concerning the mAT group, the targeted activity was localized in the anterior wall in 4 cases (33.3%), in proximity to PVs in 3 cases (25%), along the left ridge in 2 cases (16.6%), and at the roof, in the free wall and along the CTI in 1 case (8.3%), respectively. Low voltage areas (< 0.1 mV) were detected in all mAT cases and colocalized with the origin site. Over a median of 288 [248-349] days of follow-up, 5 (3.1%) patients suffered from an AT/AF arrhythmia recurrence: 3 (3.1%) were in the MAT group, 1 (2%) in the focal AT and 1 (8.3%) in the mAT group.

CONCLUSION

A novel automated algorithm for mAT identification, coupled with ORION catheter, enables mAT description and transcatheter ablation of the localized origin of this rare form of AT results in a satisfactory procedural success rate.

TRIAL REGISTRATION

Catheter Ablation of Arrhythmias With High-Density Mapping System in the Real World Practice (CHARISMA). http://clinicaltrials.gov/ Identifier: NCT03793998.

Peri-Mitral Atrial Tachycardia Following Transcatheter Aortic Valve Replacement

Transcatheter aortic valve replacement (TAVR) is commonly used to treat severe aortic stenosis. Although atrial fibrillation and conduction disturbances are well-known complications, peri-mitral atrial tachycardia (PMT) post-TAVR is less frequently reported. A 75-year-old man with persistent PMT 1-year post-TAVR was managed successfully through radiofrequency catheter ablation. High-density 3-dimensional mapping identified a macro-reentrant circuit and a slow-conduction area adjacent to the transcatheter aortic valve implantation site, diagnosed as counterclockwise PMT. Ablation resulted in tachycardia termination, with no recurrence at follow-up. This case highlights structural alterations from TAVR as potential contributors to arrhythmic substrates. The rarity and successful management of PMT post-TAVR contribute significant insights, emphasizing the need for vigilant arrhythmic monitoring and tailored interventions. This case underscores the importance of recognizing and managing rare arrhythmic complications following TAVR, enhancing patient outcomes through precise diagnostic and interventional strategies.

Atypical Atrial Flutter: Electrophysiological Characterization and Effective Catheter Ablation

Atrial flutter (AFL), defined as macro-re-entrant atrial tachycardia, is associated with debilitating symptoms, stroke, heart failure, and increased mortality. AFL is classified into typical, or cavotricuspid isthmus (CTI)-dependent, and atypical, or non-CTI-dependent. Atypical AFL is a heterogenous group of re-entrant atrial tachycardias that most commonly occur in patients with prior heart surgery or catheter ablation. The ECG pattern is poorly predictive of circuit anatomy but may still provide mechanistic insight. AFL is difficult to manage medically and catheter ablation is the preferred treatment for most patients. Recent progress in technology and clinical electrophysiology has led to detailed characterization of re-entry circuits and effective ablation strategies. Combined activation and entrainment mapping are key to identifying the re-entry circuit. The presence of a slow-conducting isthmus, localized re-entry, dual-loop re-entry or bystander loops may lead to misleading activation maps but can be identified by electrogram examination and entrainment mapping. In the occasional patient without inducible AFL, substrate mapping in sinus rhythm may be a viable strategy. Long-term ablation success requires the creation of a transmural continuous lesion across a critical component of the re-entry circuit. Procedural endpoints include bidirectional conduction block across linear lesions and non-inducibility of atrial tachycardia. The present review discusses the epidemiology, mechanisms, ECG characteristics, electrophysiological characterization, and catheter ablation of atypical AFL.

Long-term outcomes after catheter ablation for idiopathic atypical atrial flutter

BACKGROUND

Idiopathic atypical (non-cavotricuspid isthmus-dependent) atrial flutter (IAAFL) may be seen in patients without structural heart disease and without previous cardiac surgery or ablation.

OBJECTIVE

This study sought to determine the patient characteristics, electrophysiologic and electroanatomic properties, and clinical outcomes after ablation in patients with IAAFL.

METHODS

We retrospectively compared IAAFL patients with cavotricuspid isthmus-dependent AFL (C-AFL) patients undergoing catheter ablation. The primary outcome was a composite of death from cardiovascular causes, ischemic stroke, and hospitalization for worsening of heart failure.

RESULTS

Of 180 patients who underwent catheter ablation for AFL, 89 were included in this study (22 IAAFL and 67 C-AFL). Electrophysiologic study showed significantly longer intra-atrial conduction time and lower atrial voltage during sinus rhythm in the IAAFL group compared with the C-AFL group. The atrial scar was observed in all 22 IAAFL patients, with the most common sites being the posterior or lateral wall of the right atrium in 10 (45.5%) and the anterior wall of the left atrium in 8 (36.4%). During 3.5 ± 2.8 years of follow-up, the composite primary end point occurred significantly more frequently in the IAAFL group (hazard ratio [HR], 3.45; 95% confidence interval [CI], 1.20-9.89; P = .015). In multivariable analysis, brain natriuretic peptide levels (HR, 1.01; 95% CI, 1.00-1.01, per 1 pg/mL; P = .01) and IAAFL (HR, 4.14; 95% CI, 1.21-14.07; P = .02) were independently associated with the primary outcome.

CONCLUSION

IAAFL in patients had distinct electrophysiologic features suggestive of atrial cardiomyopathy. These patients are at risk for development of cardiovascular adverse events after ablation.

Atypical atrial flutter catheter ablation in the era of high-density mapping

BACKGROUND

Mapping and ablating atypical atrial flutters (AAFLs) have evolved greatly with advances in high-density 3D mapping systems over the last years.

METHODS

The objectives are to evaluate the feasibility of AAFL catheter ablation based on high-density mapping and minimizing entrainment and to better characterize AAFL circuits. Consecutive patients who underwent AAFL ablation using the EnSite Precision™ system and HD Grid™ mapping catheter (Abbott, Chicago, IL) between 06/2018 and 1/2022 were included. Mitral isthmus-dependent and roof-dependent AAFLs were classified as conventional circuits. All other AAFL circuits were classified as non-conventional circuits and were defined based on the location of the critical isthmus.

RESULTS

Sixty-two patients underwent AAFL ablation (mean age 68±11 years). A total of 95 AAFLs were mapped and 92 (97%) were successfully ablated. Fifty-three (85%) patients had a previous AF/AFL ablation. Forty-four (46%) AAFL circuits were classified as conventional and 51 (54%) as non-conventional. Conventional AAFL circuits had longer critical isthmuses (19.0±9.0 vs 10.8±6.3mm, p<0.001), a lower prevalence of slow conduction at the critical isthmus (59% vs 86%, p=0.005), and a longer radiofrequency time to AAFL termination (117±119 vs 51±66 s, p=0.002). Entrainment was attempted in 19 (20%) flutters and its use declined significantly over the study period. Procedural success rates remained high whether entrainment was used or not. Freedom of any atrial tachycardia was 65% over a follow-up of 13.8±9.0 months.

CONCLUSIONS

AAFL catheter ablation can be achieved with high procedural success rate using a contemporary strategy based on high-density mapping alone. Non-conventional circuits are frequent and present unique electrophysiological characteristics.