Beyond the usual suspects: a rare case report of left anterior descending artery to pulmonary artery fistula with concomitant atherosclerotic coronary artery disease.

Introduction: Coronary artery fistulas (CAFs) are rare vascular anomalies that may remain asymptomatic or present with symptoms mimicking coronary artery disease (CAD). In individuals with coexisting coronary atherosclerosis, fistulas that originate from the left anterior descending artery (LAD) and end in the pulmonary artery are extremely rare and can complicate the clinical picture. Case presentation: A 46-year-old man, an ex-smoker with a previous non-ST-elevation myocardial infarction, presented with worsening chest pain and dyspnea. Coronary angiography demonstrated severe left anterior descending artery (LAD) stenosis, diagonal artery occlusion, and a fistulous communication arising from the proximal LAD with focal aneurysmal dilatation draining into the main pulmonary artery. Cardiac computed tomography (CT) confirmed multiple fistulous tracts between the LAD and the pulmonary artery. Following a multidisciplinary discussion, the patient underwent surgical fistula ligation with double-vessel coronary artery bypass grafting (CABG). The postoperative course was uneventful, with complete symptom resolution at six-month follow-up. Discussion: The coexistence of an LAD-pulmonary artery fistula with significant CAD is rare and poses diagnostic and therapeutic challenges. For precise anatomical delineation and surgical planning, multimodality imaging was crucial. Surgical ligation of the fistula, combined with CABG, allowed definitive treatment of both pathologies in a single procedure. Conclusion: This case highlights the importance of considering CAFs as a potential coexisting pathology in adults presenting with angina and coronary artery disease. Recognition of such anomalies is essential to guide appropriate management and prevent complications.