Background

Atrial fibrillation (AF) ablation became an effective treatment option, and cryoballoon ablation (CBA) is a standard procedure for pulmonary vein isolation (PVI). Potentially life-threatening complications including cardiac tamponade exist. Intracardiac echocardiography (ICE) can be used to guide transseptal puncture, to visualize balloon positioning, to observe diaphragmatic motion, and to exclude pericardial effusion. There is still controversy if ICE is beneficial for the patient in the overall safe and effective CBA procedure. 

Methods 

A subanalysis of the prospective multi-center FREEZE Cluster Cohort Trial (NCT01360008) was performed. All patients undergoing a “PVI only” CBA procedure were included. Patients with intraprocedural transesophageal echocardiography were excluded. Two groups were formed: Group A comprises conventional CBA, group B consists of CBA procedures with ICE usage. Baseline, procedural results, and complications were compared between groups using established descriptive statistical methods.

Results

From 2011 to 2016, a total of 4189 patients were enrolled in 42 centers from eight countries, and 1906 (45.5%) patients were included in the subanalysis. The group sizes were comparable with 1066 (55.9%) in group A and 840 (44.1%) patients in Group B. Group A was significantly younger (60.6±10.8 vs. 62.4±10.5, p<0.001), with smaller left atria (40 vs. 43 mm, p<0.001), and lower rate of persistent AF (23.1 vs. 38.1, p<0.001). In group A, more patients were treated with the first generation cryoballoon (29.3 vs. 18.9%, p<0.001), and the additional cryoballoon size was less frequently used (4.5 vs. 21.7%, p<0.001). The numbers of freezes per PV were significantly lower in group A. Acute PVI was achieved in group A in 94.2%, and group B in 97.1% of PVs (p<0.001). Procedure, left atrial, and fluoroscopy times were significantly shorter in group A as compared to group B. Median absorbed radiation dose was significantly higher in group A (2911 cGyxcm2 (1349; 5471)) as compared to group B (2072 cGyxcm2 (1189; 3646)), p<0.001. Post-procedural AF recurrence was documented in 10.9% in group A and 4.2% in group B (p<0.001).

In-hospital major adverse cerebrovascular and cardiac event rates were not different between groups (5/1066 (0.5%) vs. 1/840 (0.1%)), including two deaths in group A. Procedural complications (10.4 vs. 5.1%, p<0.001), major complications (3.2 vs. 1.3%, p<0.001), and cardiac tamponade (8/1066 (0.8%) vs. 1/840 (0.1%), p=0.046) were significantly more frequently observed in group A as compared to group B, respectively. The rate of phrenic nerve palsy (PNP) unresolved until discharge was not different between groups (1.4 vs. 1.0%, p=0.35). Transient PNP with recovery until discharge was more often documented in group A (2.2 vs. 0.6%, p=0.005). A non-significant trend for more groin complications were observed in group A.  

Conclusion

The use of ICE in CBA procedures was associated with significantly fewer complications including cardiac tamponades. In the ICE guided group, higher acute success rates were achieved, and significantly longer procedure, LA, and fluoroscopy times were observed. These findings might be related to more applications, a higher double balloon rate, and a more frequent use of the advanced CBA system. The results suggest that CBA is safer in combination with ICE. However, the study was not powered for this subanalysis and the study design might be prone to bias.