ABC | Volume 111, Nº2, August 2018

Original Article Marino et al 123 I-MIBG Scintigraphy in Heart Failure Arq Bras Cardiol. 2018; 111(2):182-190 Table 2 – Scintigraphic parameters of myocardial dysfunction ( 123 I-MIBG) in CCC, non-CCC and HT patients 123 I-MIBG CCC non-CCC HT p Early HMR* 1.73 ± 0.24 1.62 ± 0.21 1.26 ± 0.10 < 0.001 a Late HMR* 1.58 ± 0.27 1.44 ± 0.16 1.20 ± 0.12 < 0.001 a WO% 41.60 ± 21.41 47.37 ± 14.19 43.29 ± 23.02 0.057 b CCC: chronic Chagas cardiomyopathy; non-CCC: cardiomyopathy other than Chagas disease; HT: heart transplant; early HMR: ratio of the heart/mediastinum radioactive counts estimated on 15-minute images (early uptake); late HMR: ratio of the heart/mediastinum radioactive counts estimated on 180-minute images (late uptake); WO%: cardiac washout of 123 I-MIBG, expressed as percentage; (*): values expressed as mean and standard deviation. Note: The probability of statistical significance refers to analysis of variance based on (a) repeated measures and (b) analysis of variance. The literature on HF has reported reduced late HMR values (1.80), 24 with a correlation between a reduction in uptake and worse prognosis, expressed as a higher number of cardiac events and higher mortality. 13,24,25 The late HMR values found for our patients with HF (Table 2) were lower than those adopted by different authors using cutoff point values < 1.75 (sensitivity of 84% and specificity of 60%), 13 < 1.68, 25 or even, more restrictive, < 1.60. 24 The HMR values found for HT patients (1.20 ± 0.12) were lower than those found for individuals with HF, with statistical significance (p<0.001), which is aligned with that reported in the literature for patients within the first post-HT year, specially individuals with idiopathic heart disease. 23,29 It is worth noting that the patients of this study were on regular use of beta-blockers and ACEI, which do not interfere directly in the uptake of noradrenaline. However, by improving the cardiac performance, and, thus, the sympathetic tone, they increment the 123 I-MIBG uptake. 34 Thus, supposedly, the HMR values of our patients are overestimated, reinforcing their sympathetic dysfunction degree. Considering that the late HMR values of individuals with CCC (1.58 ± 0.27) are overestimated, and that Gadioli et al. 21 Figure 2 – Early and late HMR of 123 I-MIBG in CCC or non-CCC or HT patients. Early HMR - ratio of the heart/mediastinum radioactive counts estimated on 15-minute images (early uptake); late HMR: ratio of the heart/mediastinum radioactive counts estimated on 180-minute images (late uptake). Groups: CCC: chronic Chagas cardiomyopathy; non-CCC: cardiomyopathy etiology other than Chagas disease; HT: heart transplant. p = 0.251 p = 0.002 p < 0.001 p = 0.002 p = 0.126 p = 0.011 2.25 2.00 1.75 1.50 1.25 1.00 2.00 2.20 1.80 1.60 1.40 1.20 1.00 CCC non-CCC HT Group CCC non-CCC HT Group early HMR late HMR have reported a significant correlation between late HMR values of 1.68 ± 0.19 and severe ventricular arrhythmias, we assumed that the sympathetic dysfunction was more severe in the CCC group because of its arrhythmic findings as compared to the non-CCC group. 20,22 However, in our study, those values did not differ significantly from those of the non-CCC group (1.44 ± 0.16), even when statistically adjusted to age and LVEF (p = 0.111). This fact might be explained by the advanced HF stage of our patients, when sustained autonomic sympathetic dysfunction represents a deleterious mechanism in the pathogenesis of HF itself, 8-10,13,24,25,33 independently of etiology, which is aligned with the report by other authors. 13 On the other hand, the importance of sympathetic dysfunction in CCC has been questioned by different authors because of: variation in the intensity of denervation; absence of correlation between parasympathetic denervation and myocardial dysfunction extent; 19 presence of autonomic dysfunction in the early stages of Chagas disease; 4,15,19 correlation between persistence of themyocardial inflammatory process and those patients’ morbidity and mortality, 35 despite the serum levels of catecholamines. 185