Measurement of myocardial infarct size by electron beam computed tomography -: A comparison with 99mTc sestamibi

RATIONALE AND OBJECTIVES. The authors sought to determine, using a variety of regional left ventricular ejection fraction (EF) and wall thickening (WTh) criteria, the applicability to measure left ventricular (LV) infarct size using electron-beam CT (EBCT) in patients as compared with technetium 99m (Tc-99m) sestamibi scanning as reference standard. METHODS. Twelve patients (age 57 +/- 11 years) underwent Tc-99m sestamibi scanning and EBCT at hospital discharge after an acute index anterior myocardial infarction. Left ventricular infarct size was defined using standard Tc-99m sestamibi scanning. Regional EF and WTh were analyzed on each EBCT scan with use of a floating epicardial centroid method. In five contiguous LV tomograms, the amount of infarcted myocardium was estimated using the following EF and WTh criteria: EF less than or equal to 35%, 30%, 25%, 20%, and WTh less than or equal to 2 mm, 1 mm, and 0 mm. RESULTS. Infarct size measured with Tc-99m sestamibi was 33.3% (+/- 18.3%) (mean +/- SD, range 6%-54%) of the LV. Using an EF less than or equal to 35% or absolute WTh less than or equal to 2 mm as criteria for infarcted myocardium, EBCT yielded 28% (+/- 17%) and 27% (+/- 16%), respectively (P = NS, paired Student's t test, versus Tc-99m sestamibi). Although, with use of the other criteria, EBCT tended to underestimate infarct size compared with Tc-99m sestamibi, a close correlation across the entire range of infarct size determinations (range, 0.72-0.82) regardless of the underlying criteria suggested an internal consistency of the data. CONCLUSIONS. Quantitative analysis of regional myocardial function by EBCT allows an estimate of anterior infarct size when compared with Tc-99m sestamibi. This suggests that in addition to previously established applications after acute myocardial infarction such as examination of cardiac volumes and mass, EBCT also may provide for infarct size determination.