I-123 METAIODOBENZYLGUANIDINE MYOCARDIAL SCINTIGRAPHY FOR PREDICTION OF RESPONSE TO P-BLOCKER THERAPY IN PATIENTS WITH DILATED CARDIOMYOPATHY

This study was performed to evaluate whether iodine-123 metaiodobenzyl guanidine (MIBG) myocardial scintigraphy could predict the response to beta-blocker therapy in patients with nonischemic dilated cardiomyopa thy (DCM). beta-Blocker therapy is effective in some patients with DCM . MIBG myocardial scintigraphy has also been suggested to be useful in evaluating the severity of myocardial damage in DCM. However, no data exist on whether MIBG imaging can be used to predict which patients w ith DCM will respond to beta-blocker therapy. We prospectively evaluat ed whether MIBG myocardial imaging was useful in predicting responses to beta-blocker therapy in patients with DCM. MIBG imaging was perform ed in 45 patients with DCM (35 men, 10 women, aged 13 to 68 years) bef ore the start of bisoprolol. The heart to mediastinum (H/M) MIBG uptak e ratio was evaluated on initial and delayed images, and the percent w ashout rate of myocardial MIBG was also obtained from these data. Of t he 45 patients, 30 (67%) responded to beta-blocker therapy, whereas 2 were resistant and 13 showed progression of heart failure or died of h eart failure. By logistic regression analysis, the H/M uptake ratio on delayed images was seen to be a good predictor of the response to bet a-blocker therapy with a threshold of 1.7 (sensitivity = 91%, specific ity = 92%, accuracy = 91%, positive and negative predictive value = 97 % and 80%, respectively). These results indicate that an H/M ratio >1. 7 on the delayed MIBG myocardial scintigraphic images provides a usefu l indication of whether patients with DCM will respond to beta-blocker therapy.