# Impact of fat on the left atrial roof identified using intracardiac echocardiography during pulmonary vein isolation procedures

## TL;DR

This study shows that fat on the left atrial roof, identified with ICE, is linked to more conduction gaps after ablation procedures for atrial fibrillation.

## Contribution

The study introduces the use of intracardiac echocardiography to identify fat on the left atrial roof and its impact on ablation outcomes.

## Key findings

- Fat on the left atrial roof was identified in 37.2% of patients using intracardiac echocardiography.
- Conduction gaps were significantly more common in patients with fat on the left atrial roof (20.0% vs. 1.7%).
- Most conduction gaps occurred when the ablation line crossed fat regions.

## Abstract

Previous studies have reported the presence of fat between the septopulmonary bundle and the septoatrial bundle on the left atrial (LA) roof. This fat may increase the wall thickness and protect the septopulmonary bundle from radiofrequency energy, potentially leading to conduction gaps.

This study aimed to determine whether fat on the LA roof can be identified using intracardiac echocardiography (ICE) and whether its presence affects the procedural outcomes of pulmonary vein isolation (PVI).

We evaluated 94 patients undergoing first-time radiofrequency catheter ablation for atrial fibrillation (60 men [63.8%]; mean age 65.7±10.7 years; 46 with paroxysmal atrial fibrillation [48.9%]) between February 2021 and September 2023. ICE was used to visualize the LA roof, and hypoechoic regions suggestive of fat were marked within the CARTOSOUND map (Biosense Webster, Irvine, CA). PVI was then performed with a personalized isolation line, avoiding fat regions when feasible.

Fat on the LA roof was identified in 35 of 94 patients (37.2%). Conduction gaps on the left pulmonary vein roof were observed in 7 of 35 patients with fat (20.0%) and 1 of 59 patients without fat (1.7%) (P=.004). Among patients with conduction gaps, 7 of 8 (87.5%) had a PVI line that crossed a fat region. No significant differences were noted in conduction gaps in other areas between the 2 groups.

The findings indicate that the presence of fat on the LA roof, as identified using ICE, may be associated with a higher incidence of conduction gaps after PVI.