Recovery of Iodine-123 Metaiodobenzylguanidine Uptake Associated with Left Ventricular Functional Recovery in a Patient with Dilated Cardiomyopathy: Endomyocardial Histological Findings before and after the Improvement of Uptake

A 58-year-old man with idiopathic dilated cardiomyopathy was treated with incremental administration of a β-blocker (metoprolol) and an angiotensin converting enzyme inhibitor (enarapril). The left ventricular end-diastolic dimension and ejection fraction improved in 8 months from 83.3mm and 17.3% to 46mm and 69%, respectively. The washout ratio and heart-to-mediastinum ratio depicted on the delayed image for iodine-123 metaiodobenzylguanidine (123I-MIBG) uptake improved from 61.7% and 1.34 to 23.1% and 1.85, respectively, in association with improvement of left ventricular indices. Successive endomyocardial biopsy specimens disclosed reduction of the degrees of vacuolation, staining irregularity, and deformity of myocyte cytoplasm and nucleus compared to the findings before therapy. In this patient with dilated cardiomyopathy 123I-MIBG scintigraphy was useful for the evaluation of the effects of therapy. We conclude that it may be informative in the estimation of the histopathological abnormalities of the myocardium.