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Catheter based pulmonary vein isolation of atrial fibrillation is becoming a mainstay of interventional treatment of atrial fibrillation. However, because RF energy involves heating viable myocardial tissue, markers of myocardial injury are increased in patients undergoing ablation. Cryoablation has been an emerging alternative to RF ablation; because, the two techniques differ in energy delivery and duration of energy applied, the associated myocardial injury may also differ between techniques, in addition to long term effects of pulmonary vein reconnection. The authors decided to compare the effect on biomarkers, patterns of pulmonary vein reconnection and clinical outcomes between Cryoablation and RF ablation.
50 patients with symptomatic drug-refractory paroxysmal atrial fibrillation were included in a prospective trial. The patients were enrolled in the cryoablation arm (n=25) and the remaining were enrolled (n=25) in the RF arm. The patients in both groups were matched by age and sex. Patients with previous catheter based ablation and left atrial diameter > 55 mm were excluded. Troponin-T was measured 18 hours after completion of the procedure. Patients that had recurrent atrial arrhythmias after 3 months were offered a repeat procedure via the RF ablation technique. During this electrophysiology study, pulmonary vein reconnection was mapped. Anti-arrhythmic drugs were discontinued after ablative procedures.
Patients were followed immediately post-procedure and Troponin-T was drawn at 18 hours. The mean level of Troponin-T in the RF group was 1.29 +/- 0.41 ug/L and 0.76 +/- 0.55 ug/L in the Cryoablation group (p=0.002). During the trial, there were patients that required additional RF ablation in the Cryoablation arm due to ineffective elimination of pulmonary potentionals. When those patients were excluded, the Troponin-T elevation was even lower in the Cryoablation arm (0.64 +/- 0.34 ug/L) and the difference between the two groups was higher (p<0.0001). When using special maneuvers such as the “pull down technique” there was no difference between the level of biomarkers within the Cryoablation group.
The follow up was extended to 1, 3, 6, and 12 months. Recurrence rates were analyzed after 3 months post-procedure. In addition, any left atrial tachycardia was also evaluated. 20% (n=5) of patients in the Cryoablation group and 28% (n=7) patients in the RF group underwent repeat atrial procedures due to recurrences. The mean number of pulmonary vein reconnections in the Cryoabation arm was 3 +/- 1 and in the RF group was 2.9 +/- 1.2 and was not statistically significant between both groups (p=0.83). Of the sites that were mapped, 74% were inferoposterior in the cyroablation group compared to only 17% inferiorly located sites in the RF group. Interestingly, left atrial tachycardia occurred in 4% of patients in the RF group and none in the Cryoablation arm. However, freedom from atrial fibrillation was 88% in the Cryoablation arm versus 92% in the RF arm after 12 months (these numbers exclude those who had a recurrence), which was not statistically significant.
The trial showed that both Cryoablation and RF ablation deliver similar rates of freedom from atrial fibrillation after 1 year. Similarly, Troponin-T levels were significantly elevated after either ablation technique. RF ablation seems to cause more myocardial injury than Cryoballon ablation, as shown by the statistically significant difference between both the groups. Despite these differences, the rate of recurrence was not different. In summary, Cryoballon ablation is an acceptable alternative to RF ablation for AF and is associated with lesser degree of myocardial necrosis without a loss in overall efficacy.
1. Kuhne M, Suter Y, Altmann D, Ammann P, Schaer B, Osswald S, Sticherling C. Cryoballoon versus radiofrequency catheter ablation of paroxysmal atrial fibrillation: biomarkers of myocardial injury, recurrence rates, and pulmonary vein reconnection patterns. Heart Rhythm 2010;7:1770-1776.
2. Chun K, Schmidt B, Metzner A, et al. The “single big cryoballoon” technique for acute pulmonary vein isolation in patients with paroxysmal atrial fibrillation: a prospective observational single centre study. Eur Heart J 2009;30:699-709.
3. Haegeli L, Kotschet E, Byrne J, et al. Cardiac injury after percutaneous catheter abaltion for atrial fibrillation. Europace 2008;10:273-275.
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