Abstract
BACKGROUND: Coronary artery aneurysm with arteriovenous fistula is extremely rare. Here we present a novel iatrogenic case of a left circumflex coronary artery (LCX) to coronary sinus fistula after mitral valve replacement (MVR). CASE SUMMARY: A 47-year-old woman with a history of MVR was diagnosed with an iatrogenic aneurysmal fistula from the LCX to the coronary sinus, causing dyspnoea. Surgical intervention included degenerated mitral and aortic valve replacement, tricuspid valve repair, and fistula ligation. Post-operative recovery was uneventful, with improved symptoms and stable cardiac function on follow-up. DISCUSSION: This case highlights the diagnostic and therapeutic challenges associated with arteriovenous fistula, particularly when they arise secondary to prior cardiac surgery. Given their rarity and potential for serious complications, early recognition and multidisciplinary planning are essential.