Pulmonary vein isolation in treatment of atrial fibrillation using radiofrequency or cryoballoon ablation: factors associated with better clinical outcomes

Abstract

Background: Electrical pulmonary vein isolation (PVI) is still regarded as a cornerstone for treatment of paroxysmal and persistent atrial fibrillation (AF). It can be achieved by different techniques. We investigated the indications and techniques of PVI using radiofrequency ablation (RFA) and cryoballoon ablation (CBA) for AF and compared the efficacy of the two techniques for persistent AF. Methods and results: First, we conducted a prospective, randomized (1:1), open-label, multi-centre clinical trial to evaluate the effectiveness of PVI performed with CBA in comparison with contact force-sensing RFA in patients with persistent AF. A total of 101 patients (52 in CBA and 49 in RFA) were enrolled and followed up for 12 months. The CBA group showed a similar clinical outcome to RFA in terms of freedom from atrial tachyarrhythmia at 12 months (69.2% in CBA vs. 61.2% in RFA, P=0.393). In addition, CBA showed comparable complications (1 in CBA vs. 4 in RFA, P=0.353), less atrial flutter (AFL) recurrence (3.9% in RFA vs. 18.0% in CBA, P=0.020), and shorter procedure and ablation time (158.9±28.9 vs. 197.9±38.4 minutes, 35.8±6.5 vs. 55.9±16.7 minutes, respectively, both P<0.001) than RFA. Second, we conducted an observational study in an RFA population, to investigate the impacts of procedural parameters on durability of PVI. We analysed the impacts of contact force (CF), power, and application time on ablation effect indicated by impedance drop (ID) in an RFA procedure with both conventional and high-power short-duration (HPSD) settings. We found that: (i) The minimum requirement of CF for effective ablation was 5 g. (ii) With CF ≥5 g, CF, power and application time can compensate for each other within restricted ranges, while the time to reach maximal ablation effect can be shortened by increasing CF or power output. (iii) The effect of HPSD ablation with 50 W for 10 s is equivalent to conventional ablation with 25 W for 40 s and 30-35 W for 20-30 s, in terms of ID. Changes of ID with increasing ablation index were similar at 30, 35 and 50 W. At 25 W they showed the same trend, but with smaller ID at the same ablation index. Third, we analysed the predictive value of procedural and biophysical parameters for the durability of PVI in a CBA population in a retrospective case-control study that used the data from 241 pulmonary veins of 71 patients who underwent a repeat AF ablation procedure. Thawing plateau time (TimeTP, defined as the time from 0 to 10℃ inside the balloon in the thawing period) was shown to be the strongest independent predictor for the durability of PVI. The relationship between TimeTP and the durability of PVI presents in a dose-proportional manner. TimeTP <15 s predicts long-term reconnection while TimeTP >25 s predicts durable PVI. In these two studies, we provided practical data for optimizing dose strategies for RFA and CBA to improve the durability of PVI. Finally, we performed a retrospective cohort study to investigate the incidence and risk factors for AF in 117 patients who suffered mostly AFL and underwent an elective cavotricuspid isthmus (CTI) ablation. During a mean follow-up period of 68 ± 24 months, 89 patients (70%) developed AF, 53 patients (42%) underwent AF ablation procedures, and 10 patients (8%) developed non-fatal ischemic cerebral events. Independent predictors for additional AF ablation included a higher CHA2DS2-vasc score (odds ratio (OR) 0.72, 95% confidence interval (CI), 0.53–0.98), documentation of both pre- and intraprocedural AF (OR 3.81, 95% CI, 1.14–12.8), and previous use of flecainide (OR 2.43, 95% CI, 1.06–5.58). We emphasized the high risk of AF occurrence and PVI in the future for AFL patients. The findings indicate that CTI block has limited prophylactic effect for AF episodes and that prophylactic PVI may be applied in selective AFL patients. Conclusions: (i) Compared with RFA, PVI performed by CBA offers shorter ablation time and procedure duration, with less AFL recurrence and similar freedom from atrial tachyarrhythmias at 12-month follow-up. (ii) Procedural parameters have predictive value and significant impacts on durability of PVI. (iii) Patients undergoing AFL ablation are at high risk of developing AF in the future and prophylactic PVI may be applied in selective AFL patients.