Prevalence and risk factors of pre-procedural left atrial thrombus in patients undergoing pulmonary vein isolation

Atrial fibrillation (AF) is increasingly treated with catheter ablation aiming at pulmonary vein isolation (PVI) (1). To decrease the peri-procedural risk of systemic embolism and stroke, patients planned for PVI undergo pre-procedural screening with transoesophageal echocardiography (TEE) (2). However, TEE is semi-invasive, often poorly tolerated by patients, and presents a risk of complications (3).

The aim of this study was to estimate the prevalence of pre-procedural left atrial thrombus detected by TEE in a large cohort of individuals planned for PVI.

This was a retrospective observational study. The study population was a cohort of all individuals who were planned for PVI at our University Hospital, Sweden, between 2018-2023. All individuals underwent TEE the same day or the day before the procedure. Individuals were identified in the local medical records using specific procedure codes for PVI, canceled PVI and TEE. The TEE images where suspicious left atrial thrombus were found underwent a second review by an independent cardiologist with long experience with the TEE.

We identified 1,928 individuals who underwent screening with TEE before a planned PVI at our University Hospital, Sweden, between 2018-2023. Among those, 5 individuals (0.26%) had a suspicious left atrial thrombus on TEE. After the second review, only 3 of those findings were assessed as thrombus. Thus, the true prevalence of peri-procedural left atrial thrombus was 0.16%. Two of those individuals had a CHADS2VASc score of 3 and one had a CHADS2VASc score of 1 but had previously undergone mitral valve repair using a ring annuloplasty.

In this large, unselected cohort of individuals planned for PVI, the risk of pre-procedural left atrial thrombus was very low. These findings can impact recommendations on patient selection for pre-procedural screening with TEE. A relevant subset of individuals with a very low probability of left atrial thrombus could be potentially safely spared from TEE, leading to a reduction of the number of unnecessary TEE procedures.