Localization of radiolabeled cardiac myosin-specific antibody in myocardial infarcts. Comparison with technetium-99m stannous pyrophosphate.

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Abstract
The myocardial uptake of radioiodinated (Fab)2 fragments of antimyosin antibody [125I-(Fab2] was compared with simultaneously administered 99mTc-pyrophosphate (Tc-PYP) in 6 dogs undergoing coronary occlusion for 24 h and 5 dogs for 72 h. Relative concentrations of both agents in normal and infarcted myocardium were related to regional blood flow as determined by distribution of 85Sr-labeled microspheres in the same animals. There was an inverse exponential relationship between 125I-(Fab)2 localization and regional blood flow in 24 h (r = 0.64) and 72 h (r = -0.80) occluded animals. The greatest uptake of 125I-(Fab)2 was observed in subendocardial layers of the center of the infarct where regional flow was most severely impaired (1-10% of normal flow). Maximal localization of Tc-PYP was observed in subepicardial layers in samples from the periphery of the infarct where flow was only moderately reduced (31-50% of normal). Differences in distribution of these 2 agents in ischemic myocardium were probably related to differences in kinetics of exit the blood pool.