Thrombus or vegetation: A mystery causing ST elevation myocardial infarction with infective endocarditis of mechanical aortic valve.

Acute myocardial infarction (MI) in the setting of infective endocarditis (IE) of mechanical cardiac valve is a rare phenomenon. The most challenging aspect is the recognition between septic embolus versus thromboembolism from prosthesis in the setting of sub-therapeutic INR especially when the coronary vasculature is normal and etiology is not clear. We are presenting a case of 56-year-old patient who developed ST elevation MI during treatment of IE of mechanical aortic valve. Cardiac catheterization showed a very subtle blockade at most distal end of LAD therefore percutaneous coronary intervention (PCI) could not be carried out. Given the lack of clear etiology between septic embolus versus prosthesis associated thromboembolism, we opted for a successful conservative approach.