BackgroundCoronary embolism is a relatively rare but important non-atherosclerotic cause of acute coronary syndrome, mainly caused by atrial fibrillation and mechanical heart valve thrombosis due to subtherapeutic anticoagulation. There have been increasing reports of bioprosthetic valve thrombosis (BPVT), but thromboembolic events are rare and mainly affect the cerebrovascular system. Coronary embolism is an extremely rare complication of BPVT.Case presentationA 64-year-old male presented with non-ST-Elevation myocardial infarction (NSTEMI) to an Australian regional health service. Three years ago, he had undergone Bentall procedure with bioprosthetic aortic valve replacement for severe aortic regurgitation and significant aortic root dilatation. Diagnostic coronary angiography revealed embolic occlusion of first diagonal branch in the absence of underlying atherosclerosis. Prior to NSTEMI presentation, the patient was clinically asymptomatic apart from the progressive increase in transaortic mean pressure gradient on transthoracic echocardiography which was first detected seven months after surgical aortic valve replacement. Transoesophageal echocardiography showed restrictions of the aortic leaflet opening but no evidence of mass or vegetation. After eight weeks of warfarin therapy, the raised aortic valve gradient returned to normal. Lifelong warfarin was prescribed, and patient remained clinically well at 39-month follow-up.ConclusionWe experienced a case of coronary embolism in a patient with probable BPVT. Reversible bioprosthetic valve hemodynamic deterioration after anticoagulation strongly supports the diagnosis in the absence of histopathology. Early moderate-to-severe hemodynamic valve deterioration warrants further investigations, including cardiac computed tomography and sequential echocardiography, to investigate for probable BPVT and consideration of timely anticoagulation initiation to prevent thromboembolic events.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12872-023-03359-9.