Comparative assessment of experimental myocardial infarction with 99Tcm-hexakis-t-butyl-isonitrile (sestamibi), 111In-antimyosin and 201Tl.

The monocationic 99Tcm-hexakis-2-methoxy-2-methyl propyl isonitrile (99Tcm-sestamibi) is a myocardial perfusion marker with potential clinical value in the diagnosis of ischaemic heart disease. The kinetics of this compound in experimental myocardial infarction in rabbits was compared to the distributions of 111In-antimyosin Fab and 201Tl at 24 h of persistent left anterior descending (LAD) coronary artery occlusion. The maximum uptake of 111In-antimyosin in the infarct was as high as 0.34% injected dose per gram (i.d. g-1), whereas normal myocardial activity was only 0.045% i.d. g-1. Maximal 201Tl and 99Tcm-sestamibi uptakes in normal myocardium were 0.16 and 0.14% i.d. g-1, respectively. Because of their faster blood clearances, 99Tcm-sestamibi and 201Tl were able to delineate regions of radiotracer distribution defects early. 111In-antimyosin required a longer circulation time for in vivo infarct visualization because of slower blood clearance. The data also demonstrated that in persistent LAD occlusion infarction in rabbits, the inverse distribution of sestamibi and 201Tl relative to antimyosin localization (indicator of myocyte necrosis) is not significantly different (I/N sestamibi = 0.213 I/N(AM) + 115.7, r = 0.91, and I/N(201Tl) = 0.181 I/N(AM) + 114.4, r = 0.89).