Giant Aneurysm in a Circumflex Coronary Sinus Fistula.

BACKGROUND: Coronary artery fistulas with giant aneurysms are rare but potentially dangerous, even in asymptomatic patients. They can lead to rupture, thrombosis, or cardiac compression, and imaging is key for diagnosis and treatment planning. CASE SUMMARY: A 61-year-old asymptomatic man was found to have a 76 × 66 mm aneurysm of the left circumflex artery. Multidetector computed tomography revealed the drainage of the aneurysm into the coronary sinus. Echocardiography showed left atrial and ventricular compression. Surgery involved aneurysm exclusion, fistula closure, and bypass grafting. Postoperative imaging confirmed success, and the patient was discharged on lifelong antiplatelet therapy. DISCUSSION: Although asymptomatic, the aneurysm's size posed a serious risk. Early surgical management, guided by imaging, led to a favorable outcome. TAKE-HOME MESSAGES: Coronary artery aneurysm associated with fistula is a rare but clinically relevant entity that requires precise multimodality imaging for diagnosis and procedural planning. Timely surgical management, guided by a multidisciplinary approach, can be performed safely and effectively, with postoperative cardioaspirin recommended to reduce thrombosis risk.