Ablation Lesion Durability: The Need to Do Better

Dear Readers,

A 63-year-old woman with a history of obesity and recurrent symptomatic paroxysmal atrial fibrillation (AF) and typical atrial flutter (AFL) status post catheter ablation at another hospital 3 months ago presented with a high burden of recurrent AF. Her initial ablation procedure included pulmonary vein isolation (PVI) and ablation of the cavotricuspid isthmus (CTI) using radiofrequency (RF) energy. Her 12-lead electrocardiogram in clinic showed AF, but interestingly, a rhythm strip showed brief termination of the AF followed by 2 sinus beats, followed by a premature atrial complex with an inferior axis, and another sinus beat followed by AF. She underwent a repeat ablation procedure, during which she converted to sinus rhythm after induction of anesthesia. Left atrial electroanatomic voltage mapping as well as inspection of the electrograms recorded at the ostium of each PV using a circular mapping catheter identified reconnection of the left superior PV, right superior PV, and right inferior PV with marked conduction delay into each PV (Figure 1). All 3 PVs were reisolated using cryoballoon ablation with 1-3 freezes in each vein. After PVI, a multielectrode mapping catheter was placed around the tricuspid annulus, and conduction through the CTI was evident with pacing. RF ablation with a few focal RF lesions in the CTI achieved bidirectional conduction block (Figure 2).

Catheter ablation to electrically isolate the PVs is limited by the risk of collateral injury. Limiting ablation time and power can lead to transient conduction block and PV reconnection, but the most common finding at the time of a repeat AF ablation procedure is PV reconnection. PV reconnection is our field’s equivalent to the interventionalists’ problem of coronary artery restenosis. What can be done to safely create ablation lesions that are more durable? The FIRE AND ICE trial found that PV reconnection is less common at the time of repeat ablation when the initial procedure was performed using a cryoballoon rather than RF current.¹ It would be logical to think that point-by-point ablation may be more vulnerable to the development of gaps; however, other studies have shown that PV reconnection is similar regardless of the energy source used.² Strategies to identify sites of ablation that might be more likely to reconnect (eg, using adenosine) have not reproducibly proven to be effective. Using high power short duration RF ablation can improve the speed of the procedure and perhaps the likelihood of first pass isolation, but it is still vulnerable to reconnection, particularly at the carina of the right-sided PVs.³ Perhaps the best approach is to wait longer and observe, but a prolonged waiting time is difficult in the electrophysiology lab, where the emphasis is on speed.

Ablation of the CTI for patients with typical AFL has a high long-term success rate. However, recent studies have shown a high rate of recovery of CTI conduction in patients undergoing CTI ablation at the time of an AF ablation procedure. One study of over 1000 patients showed that durability was 78% in patients with documented AFL vs only 58% in patients without AFL.⁴ This seems out of line with most experience, but perhaps durability was higher in patients with documented AFL because the physician waited longer after achieving block. However, both rates of reconduction are unacceptably high. Surprisingly, this low durability of CTI ablation at the time of AF ablation suggests that we are not waiting long enough to make sure that our lesions are going to last.

Catheter ablation to treat arrhythmias is dependent on hardy ablation lesions that can last for decades. An emphasis on faster procedures may lead to overly rushed ablation cases that result in quicker acute success, but also flimsy ablation lesions. Until new energy sources such as pulsed field ablation are available to create more durable lesions, we need to do our best to make sure that the ablation lesions we are currently creating are immortal. 

Bradley P. Knight, MD, FACC, FHRS

@DrBradleyKnight
Editor-in-Chief, EP Lab Digest

Disclosures: Dr Knight reports that he has served as a consultant, speaker, investigator, and/or has received EP fellowship grant support from Abbott, AtriCure, Baylis Medical, Biosense Webster, Biotronik, Boston Scientific, CVRx, Medtronic, Philips, and Sanofi. He has no equity or ownership in any of these companies.

References

1. Kuck KH, Albenque JP, Chun KRJ, et al. Repeat ablation for atrial fibrillation recurrence post cryoballoon or radiofrequency ablation in the FIRE AND ICE Trial. Circ Arrhythm Electrophysiol. 2019;12(6):e007247. doi:10.1161/CIRCEP.119.007247

2. Daimee UA, Akhtar T, Boyle TA, et al. Repeat catheter ablation for recurrent atrial fibrillation: electrophysiologic findings and clinical outcomes. J Cardiovasc Electrophysiol. 2021;32(3):628-638. doi:10.1111/jce.14867

3. Hansom SP, Alqarawi W, Birnie DH, et al. High-power, short-duration atrial fibrillation ablation compared with a conventional approach: outcomes and reconnection patterns. J Cardiovasc Electrophysiol. 2021;32(5):1219-1228. doi:10.1111/jce.14989

4. Kakehashi S, Miyazaki S, Hasegawa K, et al. Safety and durability of cavo-tricuspid isthmus linear ablation in the current era: single-center 9-year experience from 1078 procedures. J Cardiovasc Electrophysiol. 2021;33(1):40-45. doi:10.1111/jce.15281