Left main coronary artery-Pulmonary trunk fistula incidentally detected during acute coronary infarction: Complementary roles of coronary angiography and CCTA.

Coronary artery fistulas (CAFs) are rare vascular anomalies, and fistulas originating from the left main coronary artery (LMCA) are particularly uncommon. A 63-year-old woman with hypertension and obesity presented with acute anterior myocardial infarction and left ventricular systolic dysfunction. Coronary angiography incidentally identified a tortuous vascular tract arising from the proximal LMCA, but couldn't define its drainage site. Coronary computed tomography angiography (CCTA) demonstrated a 3.9 cm fistulous tract with an origin and maximal diameter of 6 mm, coursing anteriorly and to the right of the pulmonary trunk before draining into it. No focal aneurysmal dilatation, mural thrombus, calcification, or secondary branches were identified. The pulmonary trunk measured 29 mm, the right-sided cardiac chambers were not dilated, and transthoracic echocardiography showed no noninvasive evidence of a large hemodynamically significant left-to-right shunt or right-sided volume overload. Percutaneous coronary intervention (PCI) was performed for the culprit left anterior descending lesion, after which the symptoms resolved. The clinical course favored the LAD lesion as the dominant cause of ischemia, although a contributory fistula-related steal phenomenon was not formally assessed. Following discussion among several cardiovascular experts, conservative clinical and echocardiographic surveillance was selected. This case highlights the complementary roles of coronary angiography and CCTA in defining fistula anatomy and supporting individualized management and follow-up planning.