Cryoablation versus radiofrequency ablation of atrioventricular nodal reentrant tachycardia

Background: Ablation of the slow pathway is an established cure for atrioventricular nodal reentrant tachycardia (AVNRT). Periprocedural damage to the conduction system is a major concern during AVNRT ablation, and cryoablation (CRYO) has been suggested to improve the procedural safety compared to standard radiofrequency (RF) ablation, without reducing the procedural success. Objective: We performed a systematic review and meta-analysis of studies comparing CRYO with RF ablation of AVNRT. Methods: We searched PubMed, CENTRAL, the BioMed Central, EMBASE, CardioSource, clinicaltrials.gov, and ISI Web of Science (January 1980 to July 2013). No language restriction was applied. Two independent reviewers screened titles and abstracts to identify studies that compared the procedural outcomes of AVNRT ablation with either CRYO or RF energy. Two independent reviewers assessed the risk of bias according to the Cochrane Collaboration, and extracted patient, study characteristics, and procedural outcome data. Results are expressed as odds ratio (OR) or as weighted mean difference (WMD) with their 95% confidence interval (CI). Results: Fourteen studies (5 prospective randomized and 9 observational) with 2,340 patients (mean age range 13 to 53 years, 1,522 (65%) females) were included in the analysis. RF ablation was performed in 1,262 (54%) patients, while CRYO in 1,078 (46%) patients. Acute success (abolition of dual atrioventricular node physiology or single echo beats) was achieved in 88% of patients treated with RF versus 83% of those treated with CRYO (OR=0.72, 95%CI 0.46 to 1.13; P=0.157). RF ablation was associated with shorter total procedure time (WMD= -13.7 min, 95% CI -23 to -4.3 min; P=0.004), but slightly longer fluoroscopy time (WMD=+4.6 min 95% CI +1.7 to +7.6 min; P=0.002). Permanent atrioventricular block occurred in 0.87% RF cases and in no CRYO case (OR=3.60, 95% CI 1.09 to 11.81; P =0.035). Over a median follow-up of 10.5 months (range 6 to 12 months), freedom from recurrent AVNRT was 96.5% in the RF group versus 90.9% in the CRYO group (OR=0.40, 95% CI 0.28 to 0.58; P<0.001). At meta-regression analysis, no clinical or procedural variable had a significant interaction with the results above. Conclusions In patients undergoing AVNRTablation, RF significantly reduces the risk of long-term arrhythmia recurrence compared to CRYO, but is associated with a higher risk of permanent atrioventricular block.