Abnormal I-123 metaiodobenzylguanidine myocardial washout and distribution may reflect myocardial adrenergic derangement in patients with congestive cardiomyopathy.

Abstract

1-123 metaiodobenzylguanidine (MIBG) is a new radiopharmaceutical with properties that allow the characterization of the sympathetic innervation of several organ systems. In this study, we used MIBG with tomographic imaging to evaluate noninvasively the differences in myocardial sympathetic innervation in 14 healthy volunteers and 16 patients with severe dilated cardiomyopathy (CM). Initial (15-minute) images demonstrated no significant differences in MIBG concentration in the hearts of patients with CM and of healthy volunteers. However, the myocardial retention of MIBG was significantly reduced in the patients with CM. Expressed as the percent washout from 15 to 85 minutes, the patients with CM had a 28 ± 12% washout rate compared with 6 8% in the controls (p<O.OO1). A small subset of patients from each group imaged at 4-hour intervals demonstrated even greater disparity in washout rates. In addition, the patients with CM had significantly greater heterogeneity in the MIBG activity distribution within the myocardial images. There was 47 ± 15% intraimage variability in MIBG distribution in the patients with CM and 22±9% variation in the controls (p<O.OO1). We conclude from these data that the myocardial distribution and kinetics of MIBG in images obtained from patients with CM differ significantly from those of controls and that the MIBG patterns may be used as a relatively noninvasive means to evaluate the severity of altered adrenergic innervation in the hearts of these patients. (Circulation 1988;78:1192-

Abnormalities of Cardiac Sympathetic Innervation in Arrhythmogenic Right Ventricular Cardiomyopathy

“…20,21 However, in patients with ARVC, the present study and other reports 22 have shown that plasma catecholamines are not elevated. These findings suggest that increased synaptic norepinephrine confined to the heart 23 or enhanced myocardial sensitivity to catecholamines rather than elevated plasma levels may be responsible for increased sympathetic activity of the myocardium in ARVC.…”

Decreased Myocardial -Adrenergic Receptor Density in Relation to Increased Sympathetic Tone in Patients with Nonischemic Cardiomyopathy

“…Adrenergic presynaptic function was assessed by 123 I-metaiodobenzylguanidine ( 123 I-MIBG) imaging. 123 I-MIBG, a norepinephrine (NE) analog, is accumulated in sympathetic nerve endings through the uptake-1 mechanism and can be used to delineate cardiac sympathetic nerve distribution and function (21)(22)(23).…”

Effects of the Angiotensin-converting Enzyme Inhibitor Enalapril on Sympathetic Neuronal Function and .BETA.-adrenergic Desensitization in Heart Failure after Myocardial Infarction in Rats.

“…24,25) A decrease in myocardial MIBG accumulation and NE has been reported in heart failure 21,[26][27][28][29] and also in experimental models of MI. 19,30) In the present study, it is unlikely that reduced MIBG accumulation and NE content would be due to sympathetic denervation by the surgical procedure because MIBG accumulation and NE content did not decrease in the sham-operated rats.…”