BackgroundWith the established use of crossover stenting technique in bifurcation coronary artery lesions, added clinical benefit of final kissing of the side branch remains debatable. We report a case of a stenosis and thrombus formation of an ostial side branch after crossover stenting.Case SummaryA 38-year-old man was admitted with acute coronary syndrome complicated by acute pulmonary oedema. He was treated with stenting of the left descending artery (LAD) into the left main coronary artery (LMCA) 12 months earlier. Coronary angiography showed a filling defect in the ostial left circumflex coronary artery (LCX). Optical coherence tomography revealed neointimal growth of the LAD stent resulting in narrowing the LCX orifice and a large thrombus behind stent struts. After treatment of the lesion and optimised implantations of drug-eluting stents, the patient was transferred to the intensive care unit and monitored closely. Given his advanced ischaemic cardiomyopathy, the patient is being evaluated for heart transplantation eligibility.DiscussionStent struts across a bifurcated major side branch after crossover stenting could risk late stenosis and thrombus formation of the side branch. The clinical usefulness of routine imaging-guided kissing techniques even with good angiographic results in these cases should be evaluated.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40119-022-00270-w.