(111)Indium antimyosin antibody imaging of primary myocardial involvement in systemic diseases

Objective-The diagnosis of primary myocardial involvement in systemic disea ses is clinically relevant but difficult in the absence of specific criteri a. Whatever the underlying disease, myocytes degeneration is observed durin g the active phase of myocardial damage. The aim of this study was to asses s the diagnostic value of scintigraphic imaging with (111)Indium antimyosin antibody (AM), a specific marker of the damaged myocyte, for ongoing myoca rdial damage related to systemic diseases. Methods-40 patients with histologically confirmed systemic diseases were st udied. They were classified into two groups according to the presence (grou p 1, n=30), or the absence (group 2, n=10) of clinical, electrocardiographi c (ECG) or echocardiographic signs suggestive of myocardial involvement. Pl anar and tomographic acquisitions were obtained 48 hours after injection of AM (90 MBq). Rest (201)thallium (Tl) scintigraphy was also performed to as sess myocardial perfusion and scarring. Clinical, EGG, and echocardiographi c +/- scintigraphic evaluations were repeated during follow up (17 +/- 19 m onths) in 36 of 40 patients. Results-In group 1, 13 of 30 patients (43%) showed diffuse significant AM u ptake throughout the left ventricle (LV), and no or mild T1 abnormality. Tw o of these were asymptomatic, four had normal EGG, and two had no clinical or echographic LV dysfunction. All patients in group 2 had negative AMA sci ntigraphy and normal T1 scintigraphy. During follow up of 12 AM positive pa tients, cardiac status improved after immunosuppressive treatment was inten sified in nine cases, worsened in two cases, and remained stable in one. Du ring follow up of 24 AM negative patients, cardiac status remained stable i n 23 cases despite treatment not being increased in 20, including two patie nts with sequellary myocardial involvement. The last patient developed mild LV dysfunction after 36 months. Conclusion-AM scintigraphy allows detection of active myocardial damage rel ated to systemic diseases, with increased specificity compared with convent ional methods, and increased sensitivity in some cases. Further studies are needed to assess the potential value of AM scintigraphy as a therapeutic g uide.