ABSTRACTThe Fab fragments of antimyosin antibodies, labeled with 9mTc, were used in the scintigraphic examination of 30 patients with myocardial infarction. The ability to detect necrosis and determine its extent from the antimyosin scan were compared with the results of quantitative regional wall motion analysis by contrast ventriculography at 10 to 14 days and 99mTc-pyrophosphate imaging. Antimyosin images recorded by planar and single photon-emission computed tomography (SPECT) delineated areas of myocardial necrosis in 27 of 30 patients (90%) compared with a 91% sensitivity of pyrophosphate in 21 of 23 patients. Infarct size was determined by both antimyosin and pyrophosphate SPECT images. Results by both techniques showed a significant correlation with computer-derived hypokinetic segment length (r = .79 for both, p = .002) and peak creatine kinase (r = .9 for both, p < .01). Although sensitivity for and correlations with markers of necrosis were similar with both techniques, infarct size by pyrophosphate SPECT was 1.7 times larger than infarct size by antimyosin SPECT (p < .01). Certain zones in the infarct area were differentially labeled; the nature and irreversibility of injury within these zones remains to be clarified. Circulation 74, No. 3, 501–508, 1986.