Disappearance of myocardial perfusion defects on prone SPECT imaging: Comparison with cardiac magnetic resonance imaging in patients without established coronary artery disease

In this study, 52 patients without known prior infarction and no stress-induced ischemia on SPECT imaging were examined in both supine and prone position. The results were compared with cardiac magnetic resonance imaging (CMR) with delayed-enhancement technique to confirm or exclude myocardial infarction.There were 63 defects in supine-position images, 37 of which disappeared in the prone position. None of the 37 defects were associated with myocardial infarction by CMR, indicating that all of them represented attenuation artifacts. Of the remaining 26 defects that did not disappear on prone imaging, myocardial infarction was confirmed by CMR in 2; the remaining 24 had no sign of ischemic infarction but 2 had other kinds of myocardial injuries. In 3 patients, SPECT failed to detect small scars identified by CMR.Perfusion defects in the supine position that disappeared in the prone position were caused by attenuation, not myocardial infarction. Hence, imaging in the prone position can help to rule out ischemic heart disease for some patients admitted for SPECT with suspected but not documented ischemic heart disease. This would indicate a better prognosis and prevent unnecessary further investigations and treatment.Myocardial perfusion single-photon emission computed tomography (SPECT) is widely used to diagnose or exclude coronary artery disease. A normal perfusion SPECT result is associated with excellent prognosis [1], and the sensitivity and specificity are high for detection of stress-induced ischemia [2]. Imaging is traditionally performed in supine position, which may cause attenuation artifacts, mostly located inferiorly in men and anteriorly in women [3]. The attenuation artifacts may simulate perfusion defects, leading to false-positive identification of myocardial infarction [4].Since it is of great importance to exclude infarction in patients without previously identified coronary artery disease who do not have stress-induced ischemia, different technique