A rare right coronary artery arising from the left anterior descending artery with a critical left main lesion: a case report.

Background: An anomalous right coronary artery (RCA) arising from the left anterior descending artery (LAD) is a very rare coronary variant. When a distal left main (LM)/ostial LAD culprit lesion occurs in this setting, the myocardium at risk is substantial and revascularization decisions are time critical. Case summary: A 40-year-old non-diabetic heavy smoker presented with non-ST-segment elevation myocardial infarction (NSTEMI). Coronary angiography revealed severe distal LM/ostial LAD stenosis (80%-90%), and optical coherence tomography (OCT) confirmed plaque rupture with thrombus. An anomalous RCA arising from the proximal LAD was identified without significant stenosis, and the left circumflex artery (LCx) had no significant disease. Heart Team discussion recommended urgent coronary artery bypass grafting; however, the patient refused surgery and opted for percutaneous coronary intervention (PCI). OCT-guided PCI from the LM into the LAD was performed successfully with an excellent result. At 8-month follow-up, the patient remained asymptomatic, was exercising regularly, and was compliant with medications. ECG and transthoracic echocardiography were normal, with an left ventricular ejection fraction of 60%, and CT coronary angiography demonstrated a patent LM stent and a prepulmonic/anterior course of the anomalous RCA. Discussion: This case illustrates a very rare coronary anatomy in which a distal LM acute coronary syndrome carries substantial myocardium at risk. It underscores the value of timely Heart Team discussion and patient-centred decision-making when surgery is declined. Early intracoronary imaging-guided PCI can provide effective revascularization, preserve myocardial function, and achieve an excellent clinical outcome.