Cardiac allograft vasculopathy (CAV), also known as chronicle rejection, is a leading cause of graft (foreign heart) loss and death in patients who survive the first year after heart transplantation. The typical pathological change of CAV is gradually thickening of coronary wall in "foreign" heart due to continuous immunological reaction between donated heart and the host. In some cases, undetected CAV may silently cause graft failure with global myocardial ischemia without any documented infarction signs. Thus, continually monitoring development of asymptomatic CAV is important for selecting prophylactic strategies to get better prognosis. However, most current examinations of detecting CAV are invasive and with certain risks.