Use of iodine-123 metaiodobenzylguanidine myocardial imaging to predict the effectiveness of β-blocker therapy in patients with dilated cardiomyopathy

We studied 13 patients with dilated cardiomyopathy (DCM) and seven normal subjects. We obtained myocardial SPET images 15 min and 4 h after administration of 123I-MIBG (111 MBq). Studies were performed in the patients with DCM before and 1 and 3 months after the administration of metoprolol and in the normal subjects. We calculated the regional 123I-MIBG washout rate (r-WR) in the SPET image, and the global 123I-MIBG washout rate (g-WR) and heart-mediastinum activity ratio (H/M) using the anterior planar image. We classified patients into those showing a ≥5% increase in LV ejection fraction (LVEF) at 3 months compared with LVEF values before the treatment (group I, n=7) and those showing a <5% increase in LVEF (group II, n=6). In normal subjects, the r-WR values in each of the anterior, lateral, septal and inferior segments were significantly lower than those in groups I and II. These values were 18%±9%, 18%±15%, 20%±12% and 21%±15%, respectively. This study demonstrated that with regional assessment 123I-MIBG SPET imaging can be used to predict the functional improvement of LVEF at 1 month of β-blocker therapy in patients with DCM. (orig./VHE). With 4 figs., 1 tab