Transient ischaemic attack due to incidental late electrical isolation of the left atrial appendage: a case report.

Background: Electrical isolation of the left atrial appendage (LAA) during catheter ablation may increase the risk of thrombo-embolism, even in patients with low stroke risk scores and sinus rhythm. Late incidental isolation of the LAA has been rarely reported as a cause of transient ischaemic attack (TIA). Case summary: A 73-year-old woman with a CHADS2 score of 0 underwent three catheter ablation sessions for long-standing persistent atrial fibrillation. Incomplete anterior mitral line ablation during the first and second sessions led to recurrent mitral flutter. At the third session, mitral flutter was successfully terminated by linear ablation at the left mitral isthmus, and electrical conduction to the LAA remained via the anterior LA wall. Anticoagulation was discontinued post-ablation. Five years later, she developed a TIA despite maintaining sinus rhythm. Four years after the TIA, she presented with atrial tachycardia. Voltage mapping during a fourth ablation revealed extensive anterolateral LA scarring and the absence of LAA electrograms, consistent with late incidental LAA isolation. Given her thrombo-embolic risk, percutaneous LAA closure with a WATCHMAN FLX device was successfully performed. Discussion: This case suggests that linear ablations forming a substrate around the LAA may lead to its progressive electrical isolation over time, increasing thrombo-embolic risk despite sustained sinus rhythm and low stroke risk scores.