Left atrial size is a critical factor for selection of the optimal catheter ablation system for pulmonary vein isolation – pulsed field ablation or cryoballoon?

Background
Anatomy and size of the left atrium (LA) are important factors influencing performance of pulmonary vein isolation (PVI) procedures, especially when using single-shot devices. Due to unfavourable angles in enlarged atria, achievement of pulmonary vein (PV) occlusion may be challenging using cryoballoon (CB) systems. In smaller atria, there is sometimes less space for placing the device on the PV. Both situations may result in prolonged procedural and fluoroscopy times (FT).

Objective
The aim of this study was to determine which catheter system is most suitable for different atrial sizes.

Methods
We retrospectively analysed data from a cohort of 305 consecutive patients undergoing PVI between 11/2023 and 09/2024, including 206 with paroxysmal and 99 with persistent atrial fibrillation. Patients were divided into three groups: group A (n= 50) were ablated with a pentaspline pulsed field ablation (PFA) catheter, group B (n=45) with a circular PFA catheter, and group C (n=210) with a CB catheter. A normal LA size was present in 163 patients and 142 had a dilated LA (LAVI >34 ml/m², LA >23.1 cm², or >47.5 x 57 mm in short or long axis). The LA dwell time, the required FT, and the dose-area product (DAP) were chosen as surrogate parameters for procedural feasibility. Values are shown as median [IQR].

Results
The PVs were isolated in all patients.
Groups A and B demonstrated shorter LA dwell times compared to group C (46 [37-55.3] min and 53 [44.5-61.5] min vs. 58.5 [50-70.3] min; p<0.001 and p=0.006, respectively). This effect was particularly evident for enlarged LA (40.5 [33-52] min and 55.5 [46-66.3] min vs. 61.5 [52-74.5] min; p=0.001 and p=0.037, respectively). In normal-sized LA an advantage was observed only for group A but not for group B vs. group C (46.5 [38-56] min and 48 [43-58] min vs. 55.5 [48-66] min; p<0.001 and p=0.074, respectively).
In contrast, groups A and B required more FT than group C (12.3 [9-14.5] min and 11.28 [9.7-13.7] min vs. 9.0 [6.6-12.4] min; p<0.001 and p=0.002, respectively). This effect was more apparent in normal-sized LA (12.4 [9.1-14.5] min and 10.6 [10.1-13.1] min vs. 8.2 [6.2-10.5] min; p<0.001 and p=0.008, respectively). This disadvantage was also evident for the DAP of group A but not that of group B vs. C (4.9 [3-7] Gy*cm² and 3.4 [2.3-7] Gy*cm² vs. 2.8 [1.9-4.1] Gy*cm²; p<0.001 and p=0.32, respectively). For enlarged LA, there was no difference in FT or DAP between the groups.
Further analyses showed that an enlarged LA in group C was associated with longer LA dwell and fluoroscopy times (enlarged vs. normal-sized LA: LA dwell time 61.5 [52-74.5] min vs. 55.5 [48-66] min, p<0.011; FT 9.7 [7.7-13.2] min vs. 8.2 [6.1-10.5] min, p=0.001). This effect was not evident for patients in groups A and B.

Conclusion
In enlarged LA, both PFA systems showed shorter LA dwell times without adverse FT and DAP compared to the CB system. Due to the difficulty in sufficiently occluding PVs with the CB in some patients with dilated LA, the PFA systems appear to be the better alternative.
In normal-sized LA the CB system appears to be more favourable with a lower radiation exposure, especially compared to the pentaspline catheter. A reason for the increased radiation exposure in PFA systems may be attributed to the more frequent repositioning of the PFA devices. Additionally, in small LA, optimal positioning of the shaped pentaspline catheter on the right inferior PV could be challenging due to its size.