# Safety and efficacy of the second-generation cryoballoon for left atrial appendage electrical isolation in canines

## TL;DR

This study tested a second-generation cryoballoon for isolating the left atrial appendage in dogs, finding it effective but with some safety concerns.

## Contribution

The study presents a novel animal experiment confirming the safety and feasibility of second-generation cryoballoon ablation for LAAEI.

## Key findings

- LAAEI was achieved in all 10 canines with a 100% acute success rate.
- LAA flow velocity decreased significantly after ablation but partially recovered over time.
- No blood clots were observed, and the LAA tissue was replaced by fibrous tissue.

## Abstract

Left atrial appendage electrical isolation (LAAEI) has demonstrated a significant enhancement in the success rate of atrial fibrillation (AF) ablation. Nevertheless, concerns persist about the safety of LAAEI, particularly regarding alterations in left atrial appendage (LAA) flow velocity and the potential risks of thrombus. This study aimed to assess the efficacy and safety of LAAEI, investigating changes in LAA flow velocity in canines.

The study comprised a total of 10 canines. The LAAEI procedure used by a 23 mm cryoballoon of the second generation was conducted at least 180 s. Intracardiac ultrasonography (ICE) was employed to quantify the velocity flow of the LAA both prior to and following LAAEI. Following a 3-month period, subsequent evaluations were performed to assess the LAA velocity flow and the potential reconnection. Histopathological examination was conducted. Left atrial appendage electrical isolation was effectively accomplished in all canines, resulting in a 100% acute success rate (10/10). The flow velocity in the LAA showed a notable reduction during LAAEI as compared with the values before the ablation procedure (53.12 ± 5.89 vs. 42.01 ± 9.22 cm/s, P = 0.007). After the follow-up, reconnection was observed in four canines, leading to a success rate of LAAEI of 60% (6/10). The flow velocity in the LAA was consistently lower (53.12 ± 5.89 vs. 44.33 ± 10.49 cm/s, P = 0.006), and no blood clot development was observed. The histopathological study indicated that there was consistent and complete injury to the LAA, affecting all layers of its wall. The injured tissue was subsequently replaced by fibrous tissue.

The feasibility of using cryoballoon ablation for LAAEI was confirmed in canines, leading to a significant reduction of LAA flow velocity after ablation. Some restoration of LAA flow velocity after ablation may be linked to the passive movement of the LAA and potential reconnecting. However, this conclusion is limited to animal study; more clinical data are needed to further illustrate the safety and accessibility of LAAEI in humans.

Graphical AbstractOur study represents an infrequent and novel animal experiment to confirm the safety and efficacy of the cryoballoon (CB) ablation for left atrial appendage electrical isolation (LAAEI) in canines. Although second-generation cryoballoon (CB2)-induced LAAEI is a feasible technique in canines, the LAA velocity flow often decreases after ablation, and some recovery of LAA flow velocity is mostly linked to the passive movement of the LAA and left atrial, as well as the possibility of potential reconnection. The intracardiac ultrasonography (ICE)-guided transseptal puncture obtained the effective and safe outcomes in our canine study and substantially reduced X-ray exposure.

Our study represents an infrequent and novel animal experiment to confirm the safety and efficacy of the cryoballoon (CB) ablation for left atrial appendage electrical isolation (LAAEI) in canines. Although second-generation cryoballoon (CB2)-induced LAAEI is a feasible technique in canines, the LAA velocity flow often decreases after ablation, and some recovery of LAA flow velocity is mostly linked to the passive movement of the LAA and left atrial, as well as the possibility of potential reconnection. The intracardiac ultrasonography (ICE)-guided transseptal puncture obtained the effective and safe outcomes in our canine study and substantially reduced X-ray exposure.