RELATION OF I-123 METAIODOBENZYLGUANIDINE MYOCARDIAL SCINTIGRAPHY TO ENDOMYOCARDIAL BIOPSY FINDINGS IN PATIENTS WITH DILATED CARDIOMYOPATHY

Background: Iodine-123 metaiodobenzylguanidine (I-123-MIBG) concentrat es in adrenergic neurons and has been developed for evaluation of the sympathetic nervous system. Recent studies have demonstrated that the normal heart is clearly visualized by I-123-MIBG cardiac scintigraphy, whereas abnormal I-123-MIBG myocardial uptake and washout have been d emonstrated in patients after myocardial infarction and in patients wi th congestive cardiomyopathy, long QT syndrome, and ventricular tachyc ardia. Hypothesis: Based on evidence from recent studies, it can be hy pothesized that I-123-MIBG uptake is related to histopathologic change s in the myocardium. Methods: The relation of I-123-MIBG uptake to the histologic findings for the heart was studied in 24 patients with dil ated cardiomyopathy (DCM). The study group did not include patients wi th complicating disorders that primarily affect the adrenergic nervous system. The I-123-MIBG uptake was visually assigned one of four grade s using the two criteria of the mean score for six regional uptake gra des (mean score) and the global score obtained by visual evaluation of the entire image (global score). The I-123-MIBG uptake score was also determined for the region at which the biopsy specimen was obtained ( biopsy region score). The histologic findings were evaluated by assign ing one of four grades for each of the following five factors: myocyte hypertrophy, myocardial fibrotic change, myocyte degeneration and nec rosis, mononuclear cell infiltration, and myocyte disarray. The sum fo r all grades was defined as the total score,and the global score was a lso assigned to the overall histologic findings. Results: All of the g lobal, mean, and biopsy region scores for I-123-MIBG uptake correlated significantly with the global and total scores for the histologic fin dings. Among the histologic factors, myocyte degeneration showed score correlated with all global, mean, and biopsy region scores for the up take. Myocyte hypertrophy was associated weakly with the I-123-MIBG up take scores. Conclusion: These results indicate that I-123-MIBG uptake imaging is associated with histopathologic abnormalities in patients with DCM.