Specific binding of 99MTc-antimyosin to necrotic human myocardium: clinicopathologic correlations

99mTc-antimyosin antibody imaging for the detection of acute myocardial infarction in human beings

111In-antimyosin imaging is a highly sensitive and specific technique for the detection of myocardial necrosis. Two new methods of labeling antimyosin with 99mTc have been developed, and were compared with the standard 111In-antimyosin imaging technique in 29 patients with acute myocardial infarction. Fourteen patients (group I) received directly labeled 99mTc-antimyosin, and 15 (group II) were given RP-1 conjugated 99mTc-antimyosin. 99mTc-antimyosin imaging was performed at 6, 12, and 24 hours, and 111In-antimyosin imaging was done at 24 and 48 hours following injection. The images were interpreted by three blinded observers. In group I, 99mTc-antimyosin uptake could be detected in 3, 6, and 12 cases at 6, 12, and 24 hours, respectively, compared with only 8 cases at 24 hours with 111In-antimyosin. At 48 hours all patients showed 111In-antimyosin uptake. In group II, 99mTc-antimyosin uptake could be detected in 2, 3, and 6 cases at 6, 12, and 24 hours, respectively, compared with 8 and 12 cases at 24 and 48 hours, respectively, with 111In-antimyosin. Gated blood pool studies could be obtained in all patients following 99mTc-antimyosin injection and could be used to identify regional wall motion abnormalities. The plasma half-lives of 99mTc-antimyosin in group I and group II were 2.67 +/- 0.3 hours and 4.23 +/- 0.3 hours, respectively, and the plasma half-life of 111In-antimyosin was 6.3 +/- 0.4 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical role of indium-111 antimyosin imaging

Myocyte necrosis occurs in ischaemic, inflammatory and toxic heart diseases and can be detected by indium-111 antimyosin imaging. This allows a non-invasive evaluation of the site, extent and quantitation of the severity of myocardial necrosis. Simultaneous imaging of perfusion in patients with myocardial infarction allows the differentiation of necrosed and perfused areas and the varying degrees of mismatch and overlap, which has prognostic significance. 111In-antimyosin imaging is useful in the assessment of patients with unstable angina and in those for whom the diagnosis of infarction or unstable angina is not clear. In suspected myocarditis, a positive scan indicates the necessity for endomyocardial biopsy to confirm inflammation, whereas a negative scan makes the diagnosis of myocarditis unlikely. Antimyosin imaging is not useful as a marker of rejection in the 1 year post-transplant, but uptake after this period is associated with an increased rejection rate and is therefore an important tool in planning management strategies. Most patients on anthracycline treatment have demonstrable uptake, which is related to the cumulative dose and to the ejection fraction. Its role in this situation is as yet unclear. The use of new ligands and radioisotopes (99mTc) is likely to allow earlier imaging and produce improved quality.