APCU25MPC5 A double surprise: incidental dual coronary fistulas in a case of inferior STEMI with complete heart block

Introduction Coronary arteriovenous fistulas (CAF) are rare congenital or acquired vascular anomalies, with an estimated incidence of 0.1–0.2% in patients undergoing coronary angiography. Most are asymptomatic and discovered incidentally. However, the coexistence of CAF with acute coronary syndrome (ACS) remains uncommon. This case illustrates an incidental finding of dual CAFs in a patient presenting with inferior ST-elevation myocardial infarction (STEMI) complicated by complete heart block (CHB).Case Presentation A 70-year-old male, active smoker with diabetes and dyslipidaemia, presented with sudden-onset central chest pain and profuse sweating. He was alert, not tachypnoeic, but hypotensive (BP 80/56 mmHg) and bradycardic (pulse 40 bpm). Physical examination was otherwise unremarkable. ECG revealed inferior STEMI with CHB, without posterior or right ventricular involvement. Intravenous thrombolysis with methylase was administered, with resolution of chest pain, ST elevation, and heart block observed. Coronary angiography the following day showed a single-vessel disease involving distal RCA with 90% stenosis, successfully treated with plain old balloon angioplasty (POBA). Incidentally, two separate coronary artery fistulas were identified, one arising from the RCA and the other from the LAD. The patient remained hemodynamically stable and was discharged with plans for coronary CT angiography to further evaluate the fistulas and consider surgical referral.Discussion Coronary artery fistulas are often asymptomatic and rarely present alongside acute myocardial infarction. In this case, their incidental discovery raises concern for potential long-term complications. Most CAFs are congenital, though acquired forms may result from trauma, invasive procedures, or chronic inflammation. Hemodynamically significant fistulas can lead to coronary steal syndrome—where blood is diverted from the myocardial circulation—causing ischemia. Intervention is considered in symptomatic patients, large shunt volumes, or if complications such as arrhythmias, aneurysm formation, or ventricular dysfunction occur. In asymptomatic cases like this, further anatomical and functional assessment via CT or MRI helps guide management.Conclusion This case highlights the rare coexistence of incidental coronary fistulas in a patient with inferior STEMI. Although asymptomatic, such findings warrant further evaluation for potential complications and to guide the need for definitive intervention.