Learning curve using the second-generation cryoballoon ablation

To study the learning curve with the second-generation cryoballoon technology focusing on safety, efficacy and procedural characteristics.

We included 300 patients (men 64.6%, mean age 58.3 ± 12.4 years), 240 of whom were treated by four operators without prior experience in atrial fibrillation ablation and compared them with 60 consecutive patients treated by senior operator. To study the learning curves, we divided the study period into two trimesters and analyzed procedure duration, fluoroscopy times, complications, characteristics of the freeze-thaw cycles and midterm outcomes.

Hands-on help from senior operators to achieve pulmonary vein isolation was needed only in the first study trimester (24.1%), most commonly to achieve right inferior pulmonary vein isolation (55.2%). The mean procedure duration shortened from 76.7 ± 17.4 to 65.1 ± 11.4 min (P < 0.0001), and fluoroscopy time decreased from 18.5 ± 7.3 to 12.1 ± 4.3 min (P < 0.0001) for first and second trimester, respectively, and approached senior operator's results (58.2 ± 12.8 and 8.7 ± 4.5 min). Most of the major complications (one stroke, four pseudoaneurysms and one retroperitoneal hematoma) occurred during the first study trimester. Most characteristics of the freeze cycles remained unchanged in both study periods. Compared with junior operators, the senior operator achieved lower nadir temperatures in both inferior veins. However, there was no significant difference in midterm outcomes between junior and senior operators (79.5 vs 83.3%, P = 0.589).

The learning curve with the second-generation cryoballoon is steep. Inexperienced operators, trained in high-volume centers, can achieve pulmonary vein isolation safely and efficiently with short procedure and fluoroscopy times after having performed 20-30 cases.