Prophylactic Atrial Fibrillation Ablation in Atrial Flutter Patients without Atrial Fibrillation: A Meta-Analysis with Trial Sequential Analysis

Cryoballoon pulmonary vein isolation as first-line treatment of typical atrial flutter: long-term outcomes of the CRAFT trial

BACKGROUND

CRAFT was an international, multicentre, randomised controlled trial across 11 sites in the United UK and Switzerland. Given the evidence that pulmonary vein triggers may be responsible for atrial flutter (AFL) as well as atrial fibrillation (AF), we hypothesised that cryoballoon pulmonary vein isolation (PVI) would provide greater symptomatic arrhythmia reduction than cavotricuspid isthmus (CTI) ablation, whilst also reducing the subsequent burden of AF. Twelve-month outcomes were previously reported. In this study, we report the extended outcomes of the CRAFT study to 36 months.

METHODS

Patients with typical AFL and no evidence of AF were randomised 1:1 to cryoballoon PVI or radiofrequency CTI. All patients received an implantable loop recorder (ILR) for continuous cardiac rhythm monitoring. The primary outcome was time-to-symptomatic arrhythmia recurrence > 30 s. Secondary outcomes included time-to-first-AF episode ≥ 2 min. The composite safety outcome included death, stroke and procedural complications.

RESULTS

A total of 113 patients were randomised to cryoballoon PVI (n = 54) or radiofrequency CTI ablation (n = 59). Ninety-one patients reconsented for extended follow-up beyond 12 months. There was no difference in the primary outcome between arms, with the primary outcome occurring in 12 PVI vs 11 CTI patients (HR 0.97; 95% CI 0.43-2.20; p = 0.994). AF ≥ 2 min was significantly less frequent in the PVI arm, affecting 26 PVI vs 36 CTI patients (HR 0.48; 95% CI 0.29-0.79; p = 0.004). The composite safety outcome occurred in 5 PVI and 6 CTI patients (p = 0.755).

CONCLUSION

Cryoballoon PVI shows similar efficacy to radiofrequency CTI ablation in reducing symptomatic arrhythmia recurrence in patients presenting with isolated typical AFL but significantly reduces the occurrence of subsequent AF.

Cavotricuspid Isthmus-Dependent Atrial Flutter. Beyond Simple Linear Ablation

The demonstration of a peritricuspid circular movement with a zone of slow conduction in the cavotricuspid isthmus, together with the high efficacy of linear ablation and widely accepted acute endpoints, has established typical flutter as a disease with a well-defined physiopathology and treatment. However, certain aspects regarding its deeper physiopathology, ablation targets, and methods for verifying the results remain to be clarified. While current research efforts have primarily been focused on the advancement of effective ablation techniques, it is crucial to continue exploring the intricate electrophysiological, ultrastructural, and pharmacological pathways that underlie the development of atrial flutter. This ongoing investigation is essential for the development of targeted preventive strategies that can act upon the specific mechanisms responsible for the initiation and maintenance of this arrhythmia. In this work, we will discuss less ascertained aspects alongside the most widely recognized general data, as well as the most recent or less commonly used contributions regarding the electrophysiological evaluation and ablation of typical atrial flutter. Regarding electrophysiological characteristics, one of the most intriguing findings is the presence of low voltage zones in some of these patients together with the presence of a functional, unidirectional line of block between the two vena cava. It is theorized that episodes of paroxysmal atrial fibrillation can trigger this line of block, which may then allow the onset of stable atrial flutter. Without this, the patient will either remain in atrial fibrillation or return to sinus rhythm. Another of the most important pending tasks is identifying patients at risk of developing post-ablation atrial fibrillation. Discriminating between individuals who will experience a complete arrhythmia cure and those who will develop atrial fibrillation after flutter ablation, remains essential given the important prognostic and therapeutic implications. From the initial X-ray guided linear cavotricuspid ablation, several alternatives have arisen in the last decade: electrophysiological criteria-directed point applications based on entrainment mapping, applications directed by maximum voltage criteria or by wavefront speed and maximum voltage criteria (omnipolar mapping). Electro-anatomical navigation systems offer substantial support in all three strategies. Finally, the electrophysiological techniques to confirm the success of the procedure are reviewed.

Cryoballoon Pulmonary Vein Isolation as First-Line Treatment for Typical Atrial Flutter

OBJECTIVE

We aimed to compare cryoballoon pulmonary vein isolation (PVI) with standard radiofrequency cavotricuspid isthmus (CTI) ablation as first-line treatment for typical atrial flutter (AFL).

METHODS

Cryoballoon Pulmonary Vein Isolation as First-Line Treatment for Typical Atrial Flutter was an international, multicentre, open with blinded assessment trial. Patients with CTI-dependent AFL and no documented atrial fibrillation (AF) were randomised to either cryoballoon PVI alone or radiofrequency CTI ablation. Primary efficacy outcome was time to first recurrence of sustained (>30 s) symptomatic atrial arrhythmia (AF/AFL/atrial tachycardia) at 12 months as assessed by continuous monitoring with an implantable loop recorder. Primary safety outcome was a composite of death, stroke, tamponade requiring drainage, atrio-oesophageal fistula, pacemaker implantation, serious vascular complications or persistent phrenic nerve palsy.

RESULTS

Trial recruitment was halted at 113 of the target 130 patients because of the SARS-CoV-2 pandemic (PVI, n=59; CTI ablation, n=54). Median age was 66 (IQR 61-71) years, with 98 (86.7%) men. At 12 months, the primary outcome occurred in 11 (18.6%) patients in the PVI group and 9 (16.7%) patients in the CTI group. There was no significant difference in the primary efficacy outcome between the groups (HR 1.11, 95% CI 0.46 to 2.67). AFL recurred in six (10.2%) patients in the PVI arm and one (1.9%) patient in the CTI arm (p=0.116). Time to occurrence of AF of ≥2 min was significantly reduced with cryoballoon PVI (HR 0.46, 95% CI 0.25 to 0.85). The composite safety outcome occurred in four patients in the PVI arm and three patients in the CTI arm (p=1.000).

CONCLUSION

Cryoballoon PVI as first-line treatment for AFL is equally effective compared with standard CTI ablation for preventing recurrence of atrial arrhythmia and better at preventing new-onset AF.

TRIAL REGISTRATION NUMBER

NCT03401099.

Prophylactic pulmonary vein isolation in typical atrial flutter patients without atrial fibrillation: a systematic review and meta-analysis of randomized trials

BACKGROUND

New-onset atrial fibrillation (AF) is common after cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) ablation. The meta-analysis was conducted to evaluate the benefit of prophylactic pulmonary vein isolation (PVI) in typical AFL patients.

METHODS

Randomized controlled trials (RCT) comparing prophylactic PVI to CTI ablation alone in typical AFL patients without prior documentation of AF were identified in the MEDLINE, EMBASE, and Cochrane databases.

RESULTS

Four RCTs met the inclusion criteria. A total of 357 patients with follow-up of 20 ± 9 months were included. More patients in prophylactic PVI group were free from atrial arrhythmias (AA) compared with those in CTI group (69% versus 50%, OR = 2.36, 95% CI: 1.51 to 3.68; P = 0.0001). In the subgroup of age > 55, prophylactic PVI showed even higher incidence of freedom from AA. There is a lower occurrence of AF in prophylactic PVI group (27% versus 46%, OR = 0.45, 95% CI: 0.28 to 0.73; P = 0.001) and no difference of complications between prophylactic PVI group and CTI group (4% versus 2%; P = 0.33).

CONCLUSION

Our study indicated the efficacy and safety of prophylactic PVI during CTI ablation in typical AFL patients without AF history, especially for elder patients. Large prospective RCTs are warranted to confirm the benefit of prophylactic PVI in typical AFL.