Internal Mammary Artery Bypass Graft Dissection Mimicking Atherosclerotic Stenosis: Optical Coherence Tomography to Guide Stent Deferral

Angiographic narrowing of a left internal mammary artery (LIMA) bypass graft does not always reflect atherosclerotic progression. Chronic or spontaneous LIMA graft dissection may be identified using optical coherence tomography (OCT). A patient with severe multivessel coronary disease and a history of coronary stenting and triple coronary artery bypass grafting presented with non-ST-elevation myocardial infarction. Coronary angiography demonstrated critical left main-left circumflex disease, extensive left anterior descending artery in-stent restenosis, an occluded venous graft, and eccentric mid-LIMA narrowing. Urgent native-vessel revascularization restored Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow and relieved the patient's symptoms. During staged LIMA assessment 6 days later, OCT was performed using a Dragonfly OpStar imaging catheter. OCT identified the entry of a longitudinal intimal flap separating the true and false lumens over a long segment, without significant atherosclerosis in the imaged segment. The operators interpreted this "double-barrel" configuration as a nonobstructive dissection of presumed chronicity. Preserved LIMA flow and clinical stability supported stent deferral; the patient remained asymptomatic and with preserved ejection fraction at the 2-month follow-up visit. This report offers important lessons for interventionalists: intravascular imaging can distinguish dissection from apparent atherosclerotic stenosis and significantly drive further management. Inadvertent false-lumen stenting could expand the false channel, compress the true lumen, and compromise graft perfusion. OCT clearly elucidated lesion morphology and supported clinical restraint; however, it did not independently establish dissection age or an exact mechanism of dissection.