Late Defect on Delayed Contrast-enhanced Multi–Detector Row CT Scans in the Prediction of SPECT Infarct Size after Reperfused Acute Myocardial Infarction: Initial Experience

Abstract

To prospectively assess the accuracy of multi-detector row computed tomography (CT) in the prediction of infarct size after successful reperfusion of acute myocardial infarction (MI) by using single photon emission computed tomography (SPECT) images obtained 6 weeks later as the reference standard. Institutional review board approval and informed consent were obtained. A total of 34 patients (29 men and five women; mean age, 56 years +/- 13) underwent dual-phase 16-detector row CT within 3 days +/- 3 after successful reperfusion of acute MI. Iodinated contrast medium (1.5 mL per kilogram of body weight) was injected at a flow rate of 3.5 mL/sec. A first arterial phase acquisition was followed 5 minutes later by a late acquisition, without reinjection of contrast medium. A radiologist and a cardiologist used a 17-segment model in a blind analysis of images obtained during late acquisition. For each segment, presence of late defect or late enhancement was recorded. Findings were compared with SPECT studies analyzed by a nuclear medicine physician and a cardiologist 6 weeks after the acute event. CT defects were compared with SPECT defects on a segmental and per-patient basis. Mean number of segments with late defects on multi-detector row CT scans was compared with infarct size on SPECT images by using the t test. All patients had late enhancement in the infarcted myocardium. In 27 of 34 patients, a late defect surrounded by a subepicardial late enhancement was detected. Segments with late defect on CT scans were predictive of residual perfusion defects at 6-week follow-up, with sensitivity of 78%, specificity of 91%, and accuracy of 90%. On a per-patient basis, sensitivity was 93%, specificity was 100%, and accuracy was 94%. Mean number of segments with late defects on multi-detector row CT scans (ie, 3.1 segments) was not significantly different from infarct size on SPECT images (eg, 2.5 segments) (P = .2). Late defect on multi-detector row CT scans indicates residual perfusion SPECT defect and infarct size after successfully reperfused MI, with sensitivity of 93%, specificity of 100%, and accuracy of 94%.