Elevation of troponin reflects myocardial infarction. The underlying causes should be assessed, as treatment and prognosis may differ widely. Myocardial damage with non-obstructive coronary arteries requires further evaluation including magnetic resonance tomography. We report a case of significant myocardial ischemia which was unnoticed by myocardial scintigraphy but detected by positron emission tomography (PET). The 15O-water tracer allows for quantitative assessment of myocardial perfusion including regional abnormalities and may thus diagnose microvascular dysfunction.