Giant Left Atrial Appendage and Coronary Fistula With Microvascular Remodeling After Surgical Closure.

BACKGROUND: Left atrial appendage (LAA) closure reduces stroke in patients with atrial fibrillation. CASE SUMMARY: A 63-year-old man with chronic atrial fibrillation had undergone mitral valve replacement and endocardial suture closure of the LAA 5 years before presentation. One year postoperatively, a giant LAA was noted, and coronary angiography revealed a newly developed coronary-LAA fistula. Progressive enlargement of the LAA was confirmed 5 years postoperatively, with expansion of the fistulous tract on coronary angiography, ultimately leading to surgical LAA resection. DISCUSSION: Incomplete suture closure might have caused microscopic residual flow and thrombus formation within the LAA despite anticoagulation. Additionally, we speculate that the fistula developed from postoperative microvascular remodeling, potentially serving as a pathway for blood flow into the LAA. LAA resection may represent a reasonable option in selected cases. TAKE-HOME MESSAGE: Postclosure LAA enlargement, though rare, warrants evaluation for coronary-LAA fistulae because reintervention may be required.