Iodine-123 Metaiodobenzylguanidine Cardiac Imaging as a Method to Detect Early Sympathetic Neuronal Dysfunction in Chagasic Patients With Normal or Borderline Electrocardiogram and Preserved Ventricular Function

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Abstract
The indeterminate form of Chagas disease represents the most common chronic presentation. The aim of this study was to assess cardiovascular autonomic system function with I-123 metaiodobenzylguanidine (MIBG) scintigraphy in chagasic patients with normal or "borderline" electrocardiographic alterations and preserved left ventricular function evaluated by echocardiography. A total of 40 chagasic patients and 19 control subjects were included in this study. Patients had normal echocardiogram and chest radiography; no arrhythmias or myocardial ischemia; and normal exercise performance for age, gender, and body mass index. I-123 MIBG scintigraphy was performed and the heart-to-mediastinum (H/M) uptake was used as the primary predictor in the present analysis. The data analysis was performed by using Nonparametric Regression Trees and the Survival Agreement Plot. We included only patients with preserved right and left ventricular function assessed by echocardiographic methods. Variables analyzed in the regression tree were age, sex, 20 minutes and 3 hours H/M uptake after injection of I-123 MIBG, washout rate, and single photon emission computed tomography imaging. The 3 hours H/M ratio was the only significant variable (P<0.001) and for 95% of chagasic patients, this value was less than 2.19. This study presents evidence that cardiac autonomic sympathetic modulation may be affected in chagasic subjects with preserved ventricular function evaluated by echocardiography, especially in those with "borderline" electrocardiogram.

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