Pulmonary Vein Isolation for Persistent AF Using the Cryoballoon

The cryoballoon (CB) is an effective tool to isolate the pulmonary veins (PVs), and has been shown to be a safe and effective ablation approach to prevent recurrent paroxysmal atrial fibrillation (pAF) in patients who have failed medical therapy.¹ The CB was only recently approved by the FDA for use in patients with persistent atrial fibrillation (perAF), but had commonly been used off-label for that purpose. For many years, ablation strategies beyond isolating the PV have been tried in patients with perAF, but after disappointing results and publication of the STAR-II AF trial, there has been a retreat toward isolating the PVs as the sole initial approach in patients with perAF. Given the efficiency and effectiveness of the CB for the purposes of electrically isolating the PVs, it is logical to consider its use in patients with pAF, particularly when the left atrium is not significantly dilated, and the patient is in the relatively early stages of perAF. So how effective is it for perAF?

Su and colleagues recently published the results of the STOP Persistent AF trial.² In this trial, 145 patients underwent PV isolation using the CB and were followed for 12 months, with a conventional 90-day blanking period and endpoint of any atrial arrhythmia lasting more than 30 seconds. They were required to have a left atrial size <5 cm, an ejection fraction >35%, and AF that had not persisted beyond six months. Patients underwent fairly rigorous monitoring with transtelephonic monitoring every week, but loop recorders were not implanted. The success rate at 12 months was 55%. A comparison of the STOP AF Post Approval Study and the STOP Persistent AF trial is shown in Table 1. Notable differences were that the trial for perAF enrolled significantly fewer patients and patients were followed for only one year rather than three. At one year, the success rate for patients with pAF was 79%, significantly better than 55% for patients with perAF. The overall complication rates were similar in each trial. Procedural outcomes were similar in each study, with similar left atrial dwell and fluoroscopy times, but a lower need for focal ablation and less phrenic nerve injury (PNI) in the more recent trial. What is interesting is that although the success rate for perAF was lower, the redo rates in each trial were similar at about 12% at one year. This begs the question as to whether patients with perAF who had recurrences and were considered treatment failures for the purposes of the study endpoint, were actually significantly improved clinically with a lower AF burden and opted not to undergo a repeat procedure. Future studies should be conducted like the Cryoballoon vs Irrigated Radiofrequency Catheter Ablation: Double Short vs Standard Exposure Duration (CIRCA-DOSE) trial in which all patients had a loop recorder implanted to more accurately evaluate the impact of the intervention on AF burden.³

The results of the STOP Persistent AF trial using the CB for patients with medically refractory perAF suggest that the CB approach is reasonable in patients with early perAF as the initial catheter-based ablation approach. However, this trial also reminds us of how much less effective catheter ablation is for patients with AF when the AF is more persistent, and that patient expectations need to be tempered. AF has been defined as persistent when AF lasts more than 7 days, but it is likely that AF lasting more than even 24 hours is less amenable to PV isolation. A recent sub-analysis of the CIRCA-DOSE trial found that patients with AF episodes limited to less than 24 continuous hours had a significantly lower incidence of arrhythmia recurrence following AF ablation.⁴ The hazard ratio for recurrence was 0.25 for 24 hours or AF compared to 2-7 days of AF. Alternative strategies for patients with perAF are still needed. 

Disclosures: Dr. Knight reports that he is a consultant, speaker, investigator, and offers fellowship support for Abbott, Baylis Medical, Biosense Webster, Inc., BIOTRONIK, Boston Scientific, Medtronic, and SentreHEART. He has received compensation for serving as a consultant to CVRx, Inc. 

1. Knight BP, Novak PG, Sangrigoli R, et al.; STOP AF PAS Investigators. Long-term outcomes after ablation for paroxysmal atrial fibrillation using the second-generation cryoballoon: final results from STOP AF Post-Approval Study. JACC Clin Electrophysiol. 2019;5(3):306-314. doi:10.1016/j.jacep.2018.11.006. 
2. Su WW, Reddy VY, Bhasin K, et al, on behalf of the STOP Persistent AF Investigators. Cryoballoon ablation of pulmonary veins for persistent atrial fibrillation: results from the Multicenter STOP Persistent AF Trial. Heart Rhythm. 2020;S1547-5271(20)30603-2. doi:10.1016/j.hrthm.2020.06.020
3. Andrade JG, Deyell MW, Badra M, et al. Randomised clinical trial of cryoballoon versus irrigated radio frequency catheter ablation for atrial fibrillation—the effect of double short versus standard exposure cryoablation duration during pulmonary vein isolation (CIRCA-DOSE): methods and rationale. BMJ Open. 2017;7(10):e017970. doi:10.1136/bmjopen-2017-017970
4. Andrade JG, Deyell MW, Verma A, et al. Association of atrial fibrillation episode duration with arrhythmia recurrence following ablation: a secondary analysis of a randomized clinical trial. JAMA Netw Open. 2020;3(7):e208748. doi:10.1001/jamanetworkopen.2020.8748