Impact of previous left atrial ablation procedures on the mechanism of left atrial flutter: A single‐centre experience

Localized Re-Entry Is a Frequent Mechanism of De Novo Atypical Flutter

BACKGROUND

Limited data exist about the origins and mechanisms of atypical atrial flutter that occurs in the absence of prior ablation or surgery.

OBJECTIVES

The aims of this study were to report a large cohort of patients who presented for catheter ablation of de novo atypical flutters, to identify the most common locations and mechanisms of arrhythmia, and to describe outcomes after ablation.

METHODS

Demographic, electrophysiological, and outcome data were collected for patients who underwent ablation of de novo atypical flutter.

RESULTS

The mechanisms of 85 atypical flutters were identified in 62 patients and localized to the left atrium (LA) in 58 and right atrium (RA) in 27. In the LA, mechanisms were classified as macro-re-entry in 29 (50%) and localized re-entry in 29 (50%), whereas in the RA, mechanisms were macro-re-entry in 8 (30%) and localized re-entry in 19 (70%) (proportion of localized re-entry in the LA vs. RA, P = 0.08). Nine patients had both localized and macro-re-entrant atypical flutters. In the LA, localized re-entry was commonly found in the anterior LA, followed by the pulmonary veins and septum. In the RA, localized re-entry was found at various sites, including the lateral or posterior RA, septum, and coronary sinus ostium. During 39.4 months (Q1-Q3: 18.2-65.8 months) of follow-up, atrial arrhythmias occurred in 66% of patients after a single ablation and in 50% after >1 ablation. Among patients who underwent repeat ablation, compared with the index arrhythmia, different tachycardia circuits or arrhythmias were documented in 13 of 18 cases (72%).

CONCLUSIONS

Atypical atrial flutters in patients without prior surgery or complex ablation are often due to localized re-entry (approximately 50% in the LA and a higher frequency in the RA). Other atrial tachycardias commonly occur during long-term follow-up following ablation, suggesting progressive atrial myopathy in these patients.

Conduction time around the mitral valve annulus has the potential to rule out postablation perimitral atrial tachycardia

INTRODUCTION

It would be helpful in determining ablation strategy if the occurrence of perimitral atrial tachycardia (PMAT) could be predicted in advance. We investigated whether estimated perimitral conduction time (E-PMCT), namely, twice the time between coronary sinus (CS) pacing and the ensuing wave-front collision at the opposite side of the mitral annulus, correlated with the cycle length of PMAT and could predict future PMAT.

METHODS AND RESULTS

We retrospectively (retrospective cohort) and prospectively (validation cohort) investigated atrial fibrillation patients who had received pulmonary vein isolation (PVI) and in whom left atrial maps had been created during CS pacing. We calculated their E-PMCT. PMAT was observed either by provocation or during follow-up in 25, AT other than PMAT was observed in 24 (non-PMAT AT group), and 53 patients never displayed any AT (no-AT group) in the retrospective cohort. In the PMAT group of the retrospective cohort, a strong positive correlation was observed between the PMAT CL and E-PMCT (r = .85, p < 0.001). PMAT was never induced nor observed in patients with E-PMCT less than 176 ms, and the best cut-off value for PMAT was 180 ms by receiver-operating characteristic curve analysis. In the validation cohort of 76 patients, the cut-off value of the E-PMAT less than 180 ms predicted noninducibility of PMAT, with a sensitivity of 78.6%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 25.0%.

CONCLUSION

Short E-PMCT may predict noninducibility of PMAT and guide a less invasive ablation strategy.

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.

Atypical atrial flutter: review of mechanisms, advances in mapping and ablation outcomes

PURPOSE OF REVIEW

Atrial flutter (AFL) is the second most prevalent arrhythmia after atrial fibrillation (AF). It is a macro-reentrant tachycardia that is either cavotricuspid isthmus dependent (typical) or independent (atypical). This review aims at highlighting mechanism, diagnosis and treatment of atypical AFL and the recent developments in electroanatomic mapping.

RECENT FINDINGS

Incidence of left AFL is at an exponential rise presently with increase in AF ablation rates. The mechanism of left AFL is most often peri-mitral, roof-dependent or within pulmonary veins in preablated, in contrast to posterior or anterior wall low voltage areas in ablation naïve patients. Linear lesions, compared to pulmonary vein isolation alone, have higher incidence of atypical right or left AFL. Catheter ablation for atypical AFL is associated with lower rates of thromboembolic events, transfusions, and length of stay compared to typical AFL.

SUMMARY

Advances in mapping have allowed rapid simultaneous acquisition of automatically annotated points in the atria and identification of details of macro-reentrant circuits, including zones of conduction block, scar, and slow conduction.

Influence of common zones of low-amplitude activity on the mechanism and treatment of atrial arrhythmias

Background: The treatment of left atrial flutter is a problem that requires a deep understanding of the underlying complex mechanism of arrhythmia. Although a considerable experience exists already in understanding the mechanisms underlying atrial flutter after ablation or surgery, little is known about atypical forms of atrial flutter in patients who have not previously undergone ablation or other cardiac surgery. Clinical case description: We present a clinical case of interventional treatment of a patient with atypical atrial flutter who had not previously undergone surgical or interventional heart surgery. This clinical observation demonstrates the role of common zones of low-amplitude activity on the mechanism and treatment of atrial arrhythmias. Widespread areas of low-amplitude activity in the left atrium can create barriers to the propagation of excitation, which can cause atypical atrial flutter. Conclusion: When performing a surgical intervention, high-density mapping will help to visualize the mechanism of this arrhythmia. Understanding the mechanism of atypical atrial flutter will help to minimize the RF exposure during the treatment.

Ablation outcomes for atypical atrial flutter versus recurrent atrial fibrillation following index pulmonary vein isolation

BACKGROUND

Data related to electrophysiologic characteristics of atypical atrial flutter (AFL) following atrial fibrillation (AF) ablation and its prognostic value on repeat ablation success are limited.

METHODS

We studied consecutive patients who underwent a repeat left atrial (LA) ablation procedure for either recurrent AF or atypical AFL, at least 3 months after index AF ablation, between January 2012 and July 2019. The demographics, clinical history, procedural data, complications, and 1-year arrhythmia-free survival rates were recorded for each subject after the first repeat ablation.

RESULTS

A total of 336 patients were included in our study. Among these 336 patients, 102 underwent a repeat ablation procedure for atypical AFL and 234 underwent a repeat ablation procedure for recurrent AF. The mean age was 63.7 ± 10.7 years, and 72.6% of patients were men. The atypical AFL cohort had significantly higher LA diameters (4.6 vs. 4.4 cm, p = .04) and LA volume indices (LAVi; 85.1 vs. 75.4 ml/m² , p = .03) compared to AF patients at repeat ablation. Atypical AFL patients were more likely to have had index radiofrequency (RF) ablation (as opposed to cryoballoon) than recurrent AF patients (98% vs. 81%, p = .01). Atypical AFLs were roof-dependent in 35.6% and peri-mitral in 23.8% of cases. Major complications at repeat ablation occurred in 0.9% of the total cohort. Arrhythmia-free survival at one year was significantly higher in the recurrent atypical AFL compared to the recurrent AF cohort (75.5 vs. 65.0%, p = .04).

CONCLUSION

In our series, roof-dependent flutter is the most common form of atypical atrial flutter post AF ablation. Patients developing atypical AFL after index AF ablation have greater LA dimensions than patients with recurrent AF. The success rate of first repeat ablation is significantly higher among patients with recurrent atypical AFL as compared to recurrent AF after index AF ablation.

Outcome after tailored catheter ablation of atrial tachycardia using ultra-high-density mapping

INTRODUCTION

Tailored catheter ablation of atrial tachycardias (ATs) is increasingly recommended as a potentially easy treatment strategy in the era of high-density mapping (HDM). As follow-up data are sparse, we here report outcomes after HDM-guided ablation of ATs in patients with prior catheter ablation or cardiac surgery.

METHODS AND RESULTS

In 250 consecutive patients (age 66.5 ± 0.7 years, 58% male) with ATs (98% prior catheter ablation, 13% prior cardiac surgery) an HDM-guided catheter ablation was performed with the support of a 64-electrode mini-basket catheter. A total of 354 ATs (1.4 ± 0.1 ATs per patient; mean cycle length 304 ± 4.3 ms; 64% macroreentry, 27% localized reentry, and 9% focal) with acute termination of 95% were targeted in the index procedure. A similar AT as in the index procedure recurred in five patients (2%) after a median follow-up time of 535 days (interquartile range (IQR) 25th-75th percentile: 217-841). Tailored ablation of reentry ATs with freedom from any arrhythmia was obtained in 53% after a single procedure and in 73% after 1.4 ± 0.4 ablation procedures (range: 1-4). A total of 228 patients (91%) were free from any arrhythmia recurrence after 210 days (IQR: 152-494) when including optimal usual care.

CONCLUSIONS

Tailored catheter ablation of ATs guided by HDM has a high acute success rate. The recurrence rate of the index AT is low. In patients with extensive atrial scaring further ablation procedures need to be considered to achieve freedom from any arrhythmia.