The current role of infarct avid imaging.

Tc-99m pyrophosphate is the grandfather of infarct avid agents. Its value is its clinical availability and ease of use. However, its shortcomings are the delay of 2 to 3 days for reliable interpretation in nonreperfused myocardial infarction (MI) and the overarching bone activity. Antimyosin provides exquisite specificity for the detection of myocardial necrosis irrespective of the cause of the injury. Therefore, diagnosis of equivocal MI or confirmation of diffuse myocardial necrosis would benefit from the availability of In-111 labeled antimyosin Fab. The drawback of antimyosin, like that of Tc-99m pyrophosphate, is the delay, in this case because of the protracted blood clearance of the antibody protein macromolecules. Tc-99m glucaric acid, on the other hand, may fulfill the original role envisioned for antimyosin, which was to enable early, rapid diagnosis of acute MI. However, the window for the use of Tc-99m glucaric acid appears to be limited to within the first day of the acute event. Therefore, there is a potential use of both Tc-99m glucaric acid and In-111 antimyosin in tandem with Tc-99m glucaric acid, which would not only facilitate early detection and diagnosis of acute MI and diagnosis of equivocal MI, but also may permit stratification of the infarct age.