Mapping early sites of activation for AF can be used to guide ablation

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Richard Schilling

A stochastic vector-based approach to mapping and ablation of atrial fibrillation (AF) can be used to determine early sites of activation and to guide the ablation of AF drivers. Findings from targeted ablation in persistent AF using the stochastic trajectory analysis of ranked signals (STAR) mapping method were simultaneously presented at the Heart Rhythm Society’s 40th Scientific Sessions (HRS 2019; 8–11 May, San Francisco, USA) and published in the Journal of the American College of Cardiology: Electrophysiology.

Shoreh Honarbakhsh (Barts Health NHS Trust, London, UK) et al say: “Mapping leading activation sites using this novel mapping method showed consistent results, and ablation at these sites terminated atrial fibrillation or slowed cycle length substantially in a majority of patients. Ablation at these sites in addition to pulmonary vein isolation led to freedom from atrial tachycardia (AT)/AF in a high proportion of patients long-term.”

The best method for mapping and ablation of drivers of AF has not yet been determined. The study aimed to demonstrate that a stochastic vector-based mapping approach could guide ablation of AF drivers by looking at ablation response and long-term follow-up outcomes.

Researchers recruited patients with persistent AF ablation (AF duration <24 months and no previous AF ablation); 35 subjects were included. Mean age was 60.9±9.4 years, and 68.6% (n=24) were male. Patients underwent pulmonary vein isolation with further ablation guided by the stochastic trajectory of ranked signals (STAR) mapping method. The proportion of time an electrode’s activation was seen to precede its neighbouring electrode’s activation was used to determine early sites of activation. A positive ablation response at early sites of activation was defined as AF termination or a slowing of cycle length ≥30ms. Clinical relevance of the identified sites was assessed by acute ablation response and the freedom from AF/AT during 12 months follow-up.

The mean AF duration was 14.4±5.3 months (seven patients had an AF duration <12 months, 28 had an AF duration >12 months). All patients were in AF when the procedure started; 21 were performed under local anaesthetic and conscious sedation (71.4%), and the rest under general anaesthetic.

A total of 170 STAR maps were created pre- (84 maps) and post- (86 maps) pulmonary vein isolation, and the same early sites of activation were identified on 73.8±26.1% of post-pulmonary vein isolation maps. An average of 2.6±0.8 early sites of activation were ablated per patient, with study-defined ablation response achieved in all cases. Early sites of activation that resulted in AF termination were more likely to be identified on both pre- and post-pulmonary vein isolation maps than those associated with cycle length slowing (23/24 vs. 16/49; p<0.001). During a follow-up of 18.5±3.7 months, 28 (80%) patients were free from AT/AF.

Of the 32 participants who underwent STAR mapping guided ablation, 21 (65.6%) were on an anti-arrhythmic drug. There was no significant difference in the early sites of activation detection between those on an anti-arrhythmic drug and those that were not on an anti-arrhythmic drug (2.9±1.0 vs. 2.8±0.7 early sites of activation per patient; p=0.9) or in AF termination rates on ablation of early sites of activation (17/21 vs. 7/11; p=0.40).

S Honarbakhsh and colleagues say the “novel mapping method” can be used to identify early sites of activation during persistent AF, and they add: “Radiofrequency ablation at these early sites of activation resulted in a high proportion of AF slowing or termination, suggesting that these sites may represent AF drivers. Furthermore, a high proportion of patients remained free from AT/AF during long-term follow-up. Early sites of activation showed temporal consistency, being seen on most STAR maps even if shorter 30-second segments were analysed. Therefore, shorter duration of unipolar recordings may suffice to allow the identification of early sites of activation that are potentially mechanistically important.”

They also suggest that the “favourable” clinical outcome warrants further testing through a randomised controlled trial “to determine its clinical utility”.

The STAR mapping technology has now been licensed to Rhythm AI Ltd. Richard Schilling, (Barts Health NHS Trust, London, UK) a co-author of the study, told Cardiac Rhythm News: “We are very excited about the potential of this technology, which could make persistent AF ablation more accessible to patients and give better outcomes. Over the next two years we hope to further develop the technology and prove its utility in multicentre trials.”

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