| Part I. Learning Curve Analysis of Cryoballoon-based Pulmonary Vein Isolation for Atrial FibrillationBACKGROUND:Cryoballoon catheter ablation is an alternative technique to radiofrequency catheter ablation for the catheter-based treatment of atrial fibrillation, which can facilitate the procedure with a shorter learning curve compared with the latter.OBJECTIVE:To investigate the learning curve of pulmonary vein isolation using first-generation cryoballoon catheter ablation technique for atrial fibrillation.METHODS:From December 2013 to December 2014, a prospective study was carried out on the first consecutive 80 patients with drug-refractory, symptomatic atrial fibrillation who underwent primary pulmonary vein isolation for atrial fibrillation using the cryoballoon catheter ablation approach performed by a single operator in our center. The patients were coded from No.1 to 80 in chronological order of procedure and then divided into eight groups with a span of each 10 patients in sequence. Difference of procedural parameters, acute pulmonary vein isolation rate using cryoballoon catheter alone and mid-term success rate were compared between groups. Procedural-related complications were evaluated as well.RESULTS:Among the 80 patients [45 (56.3%) male, mean age 56.6± 11.6 years, mean body mass index 24.6±2.8 kg/m2],77 (96.3%) with paroxysmal AF. The median duration of atrial fibrillation was 25.5 (inter quartile range:12,69) months. The number of procedures with 28-mm,23-mm CB alone, and double CBs was 46.3%,50% and 3.7%. For each procedure, the median times of inflation only was 3 (inter quartile range:1,6), the mean times of freeze was 10.8±3.1, the mean freeze, fluoroscopic and procedural time was 37.9±9.8 min,40.6±14.7 min and 113.3± 27.7 min, respectively. Among the 8 groups coded in chronological order of procedure, with the increasing of group numbers, the times of inflation only (P= 0.001), the fluoroscopic (P< 0.001), procedural (P< 0.001) and freeze time (P= 0.011) all but the times of freeze (P= 0.251) had a trend to decrease. Compared with group 1, the times of inflation only (all P< 0.05) were less, the mean fluoroscopic and procedural time (all P< 0.01) was shorter in each of the last 7 groups, respectively.64 out of 80 (80%) patients and 301 out of 321 (93.8%) PVs were isolated successfully with cryoballoon catheter alone. Compared with group 1, the rate of acute pulmonary vein isolation was higher in each of the last 7 groups on vein level (all P < 0.05), and was higher or had a trend to be higher on patient level, respectively. The first 56 of the 80 patients had received at least one time of follow-up by January 2015. After 7.9 ±.2 months of follow-up,78.6%(44/56) patients had no recurrence of atrial fibrillation. The atrial fibrillation-free survival had no significant difference among the first 5 groups (P= 0.031). One case (1.3%) of phrenic nerve palsy, which was taken as major complication, occurred when froze a right inferior pulmonary vein with a 28-mm balloon and was recovered 9 months after procedure during follow-up. No severe procedure-related complications such as cardiac tamponade, atrial-esophageal fistula or symptomatic pulmonary vein stenosis were identified during follow up.CONCLUSION:Pulmonary vein isolation for atrial fibrillation using the cryoballoon catheter ablation is safe and effective with a relatively short learning curve of about 10 cases to achieve a relatively plateaued procedure and success rate for operators with prior experience of radiofrequency ablation for atrial fibrillation. After 7.9 ±.2 months of follow-up,78.6%(44/56) patients had no recurrence of atrial fibrillation. The atrial fibrillation-free survival had no significant difference among the first 5 groups (P= 0.031). One case (1.3%) of phrenic nerve palsy, which was taken as major complication, occurred when froze a right inferior pulmonary vein with a 28-mm balloon and was recovered 9 months after procedure during follow-up. No severe procedure-related complications such as cardiac tamponade, atrial-esophageal fistula or symptomatic pulmonary vein stenosis were identified during follow up.Part Ⅱ. Pulmonary Vein Anatomy is Associated with Balloon Cryo Kinetics during Cryoballoon Ablation for Atrial FibrillationBACKGROUND:Pulmonary vein isolation with cryoballoon catheter ablation is an established technique for the treatment of atrial fibrillation. Yet the influence of pulmonary vein anatomy on cryo kinetics during cryoballoon ablation is unclear.OBJECTIVE:To investigate the relationship between pulmonary vein anatomy and cryo kinetics during ablation for atrial fibrillation with first-generation cryoballoons.METHODS:Sixty consecutive patients with drug-refractory, symptomatic atrial fibrillation were enrolled. Pulmonary vein anatomy, including ostial diameters (long, short and corrected), the ratios between the short and long diameters, ostium shapes (round, oval, triangular, and narrow), and drainage patterns (typical, with common trunk, common antrum, ostial branch or supernumerary veins), was evaluated on multi-detector computed tomography images pre-procedure. Cryo-kinetic parameters [balloon freeze time from 0 to-30℃ (BFT), balloon nadir temperature (BNT) and balloon warming time from-30 to+15℃ (BWT)] were recorded during the procedure. The association between pulmonary vein anatomy and cryo kinetics was analyzed and the predicting values of anatomic parameters on cyo kinetics was evaluated.RESULTS:A total of 606 freezing cycles were performed in 238 out of 240 targeted pulmonary veins. A moderate negative correlation was demonstrated between BNT and corrected pulmonary vein diameter (r=-0.51, P<.001) when using 23-mm balloons, and a mild negative correlation (r=-0.32, P=.001) was found when using 28-mm balloons. Uni-and multivariate logistic regression analyses revealed that the corrected pulmonary ostial diameter (odds ratio,1.4; P=.004) predicted a BNT<-51℃ when using 23-mm CBs. Pulmonary ostium shape (pulmonary veins with an oval-shaped ostium: odds ratio,0.3; P=.033) and location (left inferior pulmonary vein:odds ratio,0.04; P =.005; right superior pulmonary vein:odds ratio,4.3; P=.025) predicted a BNT<-51℃ when using 28-mm balloons.CONCLUSION:Pulmonary vein anatomy is associated with cryo kinetics during cryoballoon catheter ablation for atrial fibrillation. Among above mentioned anatomic parameters, pulmonary vein dimension is more associated with BNT when ablation with 23-mm balloons, while ostial shapes and locations of the veins more associated with BNT when ablation with 28-mm balloons. corrected pulmonary vein diameter (r=-0.51, P<.001) when using 23-mm balloons, and a mild negative correlation (r=-0.32, P=.001) was found when using 28-mm balloons. Uni-and multivariate logistic regression analyses revealed that the corrected pulmonary ostial diameter (odds ratio,1.4; P=.004) predicted a BNT<-51℃ when using 23-mm CBs. Pulmonary ostium shape (pulmonary veins with an oval-shaped ostium: odds ratio,0.3; P=.033) and location (left inferior pulmonary vein:odds ratio,0.04; P =.005; right superior pulmonary vein:odds ratio,4.3; P=.025) predicted a BNT<-51℃ when using 28-mm balloons.Part Ⅲ. Cryoballoon Catheter Ablation for Atrial Fibrillation:the Application Value of Small Balloon in Chinese PopulationBACKGROUND:Pulmonary vein isolation with cryoballoon catheter ablation is an effective and safe approach for the treatment of atrial fibrillation. Though numerous researches are performed with the 28-mm big balloon, limited data existed with regard to the 23-mm small balloon, especially in China.OBJECTIVE:To compare the procedural parameters, safety and efficacy between the two sizes (23- and 28-mm) of the first-generation cryoballoon catheter for the treatment of atrial fibrillation in China.METHODS:From December 2013 to December 2014, eighty-one consecutive patients with drug-refractory, symptomatic atrial fibrillation were enrolled. All patients underwent pulmonary vein isolation with the first-generation cryoballoon catheter. A pre-study was carried out to assess the reproducibility of the methods evaluating the pulmonary vein ostial diameters measured on computed tomographic (CT) and venographic images prior to the study. The balloon size was determined taking the vein ostial diameters measured on CT and/or venographic images for reference. Patients were divided into two groups according to the balloon(s) used during each procedure: Group 23-and 28-mm. The procedural parameters, safety, acute isolation rates and mid-term success rates were compared between the two groups.RESULTS:Among the 81 patients [46 (56.7%) male, mean age 56.6 ± 11.5 years, mean body mass index 24.6 ±2.8 kg/m2],78 (96.3%) with paroxysmal AF. The median duration of atrial fibrillation was 27 (inter quartile range:12,72) months. The pre-analysis of reproducibility revealed that, the inter-, intra-observer intra-class correlation coefficient were 0.83 and 0.64 for pulmonary vein ostial diameter measured on venographic images, were 0.93 and 0.90 for the long diameters, and were 0.5 and 0.96 for the short diameters measured on CT images, respectively (all P<.001). The number of procedures with 23-,28-mm CB alone, and double CBs was 49.4%(40/81),46.9%(38/81) and 3.7% (3/81). Compared with Group 28-mm, the times of inflation only (median:4 vs.2; P= 0.001) was less, the mean freeze time (41.6±9.7 vs.32.9±3.5 min, P< 0.001), fluoroscopic time (46.2±15.3 vs.33.9±10.9 min, P< 0.001) and procedural time (125.0 ±27.2 vs.98.3±18.2 min, P<0.001)was shorter in Group 23-mm. The mean times of freeze between the 2 groups had no significant difference on patient level (10.1±2.2vs. 11.0±2.9, P= 0.249). However, the big balloon group needed more times of freeze to achieve isolation when froze left inferior pulmonary veins compared with the small balloon group (2.8±1.2 vs.2.2±0.4, P= 0.008). A total of 325 targeted veins were ablated among the 81 patients.64 out of 81 (79%) patients and 304 out of 325 (93.5%) PVs were isolated successfully with cryoballoon catheter alone. Compared with Group 28-mm, the rate of acute pulmonary vein isolation was significantly higher both on vein level (90.7%vs.96.9%, P= 0.021) and patient level (68.4% vs.90.0%, P= 0.018) in Group 23-mm. The rates of procedure-related complication were not significantly different between the two groups (10.5% vs.2.5%, P= 0.195). One case of phrenic nerve palsy, which was taken as major, was detected when froze a right inferior pulmonary vein with a 28-mm balloon and was recovered 9 months after procedure during follow-up. Only one case of left groin hematomas and no major complication were identified when using 23-mm balloons. A total of 56 of the 80 patients (19 in 23-, and 34 patients in 28-mm groups) had received at least one time of follow-up by January 2015 with a mean follow-up of 7.9±3.2 months,78.6%(44/56) patients had no recurrence of atrial fibrillation. The atrial fibrillation-free survival had no significant difference between 23-and 28-mm groups (84.2% vs.76.5%, P-0.726). No severe procedure-related complications such as cardiac tamponade, atrial-esophageal fistula or symptomatic pulmonary vein stenosis were identified during follow up.CONCLUSION:Pulmonary vein ostial diameters measured on CT images are more reproducible than on venographic images, and can be used as reference of balloon-size choosing during cryoballoon catheter ablation. Cryoballoon catheter ablations using 23-mm balloon can simplify the procedure and achieve a higher acute isolation rate, meanwhile do not increase the complication rate in selected patients when compared with 28-mm balloon for the treatment of atriai fibrillation in China. Further studies are needed for the criteria of balloon-choosing.
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