Background
Transesophageal echocardiography (TOE) is routinely performed to exclude intracardiac thrombi before catheter ablation of atrial fibrillation (AF) and other cardiac arrhythmias at risk of left atrial thrombi. Preprocedural conduction of TOE in every patient undergoing left atrial ablation irrespective of individual risk factors is performed in many electrophysiological centers. However, TOE is cost-intensive, invasive and bears procedural risks and discomfort for patients.

Aims
The present study prospectively evaluates a novel scoring system to indicate TOE before catheter ablation in patients at risk for left atrial thrombi based on individual patient characteristics.

Methods
Consecutive patients undergoing catheter ablation for AF, left atrial tachycardia or atrial flutter between October 2020 and October 2021 were prospectively enrolled. Pre-operative TOE to rule out intracardiac thrombi was conducted according to a novel scoring system based on current heart rhythm ad admission, CHA₂DS₂-VASc score, sufficient oral anticoagulation (OAC) during 4 weeks prior to ablation and a history of stroke or transient ischemic attack (TIA) irrespective of sufficient intake of OAC. In patients with sufficient OAC and without a history of stroke/TIA TOE was omitted. The study endpoint was the occurrence of any thromboembolism or stroke.

Results
A total of 1055 patients were analyzed. Patients were scheduled for catheter ablation as a first procedure for AF in 691 cases (65.5%), repeat AF ablation in 312 cases (29.6%), left atrial tachycardia in 15 cases (1.4%), CTI ablation in 36 cases (3.4%) and right atrial tachycardia in 1 case (0.1%). Pre-operative TOE was conducted in 336 patients (31.8%). Indication for preprocedural TOE according to our scoring system was a history of stroke in 65 cases (5.9% of patients), a history of TIA in 20 cases (1.9% of patients) and insufficient OAC in 212 cases (17.6% of patients). In the remaining 39 patients (3.9% of patients) TOE was performed after individual risk-assessment and on discretion of the treating physicians (of these 6 patients with a history of intracardiac thrombus, 1 patient with mechanical valve, 1 patient with ventricular septal defect closure, 1 patient with hypertrophic cardiomyopathy, 9 patients with impaired systolic LV function, 6 patients with severe left atrial dilatation, 1 patient on hemodialysis, 1 patient with previous cardioembolic kidney infarction). During TOE intracardiac thrombi was detected in 6 patients (0.57% of all patients; 1.8% of patients undergoing TOE) for whom catheter ablation was re-scheduled. Five of the patients with thrombus detection had previous insufficient OAC and 1 patient underwent TOE after individual decision process (reduced systolic LV function, LA enlargement).

Periprocedural thromboembolic events occurred in 2 patients (1 with pre-operative TOE, 2 strokes with proven pathology during cranial imaging). In another patient a transient visual disturbance occurred in whom cranial imaging did not detect any abnormalities and an ischemic event was estimated to be unlikely. In these patients no intracardiac thrombosis was detected during work-up.

Conclusion
Omission of pre-operative TOE based on an individual risk assessment results in low rates of peri-procedural thromboembolic events, may reduce costs and complications of invasive TOE and may enhance patient comfort.

Figure 1 Study overview

TOE=transesophageal echocardiography