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 study was designed aimed at assessing the presence and the magnitude of cardiac sympathetic dysfunction in Chagasic patients with HF. Chagasic versus non-Chagasic patients were compared, and heart transplant (HT) patients were considered as the denervated heart pattern (known to be abnormal). 23 Cardiac  123 I-metaiodobenzylguanidine ( 123 I-MIBG) scintigraphy was used to assess the patients, because it properly evaluates cardiac sympathetic dysfunction, 12,13,24,25 providing relevant parameters to understand the progression of HF. 12,13,24 Methods This is a cross-sectional study of 76 patients selected from the Heart Failure and Heart Transplant outpatient clinic of our institution from March 2014 to February 2016. The eligibility criteria for individuals with HF were: age over 18 years; left ventricular ejection fraction (LVEF) ≤ 45%; confirmed non-Chagasic or Chagasic etiology (positivity for Chagas disease confirmed by use of two different serological techniques) associated with left ventricular systolic dysfunction; 26 and accepting to participate in the study. In addition, for individuals with HF submitted to HT (comparison group or denervated heart model), 23 time from HT shorter than 12 months was required. Patients with diabetes mellitus, chronic kidney disease, chronic obstructive pulmonary disease, Parkinson disease, non-sinus heart rhythm or implantable pacemaker were excluded. The patients were studied prospectively, divided into three groups: CCC group - 25 patients with CCC (mean age, 53.3 ± 9.2 years; 17 males); non-CCC group - 25 patients with heart disease etiologies other than CCC (56% idiopathic, 36% ischemic, and 8% post-partum cardiomyopathy; mean age, 43.3 ± 12 years; 14 males); and HT group - 26 patients previously submitted to HT within less than 12 months (mean, 6.5 ± 3.8 months), with mean age of 47.3 ± 13.1 years, being 20 of the male sex. All patients provided written informed consent, which had been approved by the Ethics Committee of the institution, according to the Declaration of Helsinki. All patients underwent clinical control during the study period. Clinical, electrocardiographic (ECG at rest) and echocardiographic data were collected by the same researcher. Echocardiography was performed using the Phillips iE33® ultrasound device (Phillips Medical, Andover, MA, USA), LVEF being estimated by using Simpson’s formula. 27 Planar scintigraphy of the myocardial innervation was performed by use of slow intravenous administration of 111 MBq/3 mCi 123 I-MIBG (IPEN/CNEN), with anterior image acquisition of the chest after 15 minutes and 180 minutes on a Hawkeye® gamma-camera (GE healthcare, Milwaukie, USA), 10 min/frame, 123 I photopeak of 159 KeV, window of 20%, and low‑energy high-resolution collimator (LEHR). The heart region of interest (ROI) was drawn encompassing the entire left ventricle, while that of the superior mediastinum encompassed a square ROI of 12x12 pixels. Early and late cardiac uptakes were estimated by use of the ratio between the radioactive counts of the heart and mediastinal ROIs on early and late imaging (early HMR and late HMR, respectively). The cardiac washout rate (WO%) of 123 I-MIBG was calculated using the formula: (early heart uptake early mediastinal uptake) (late heart uptake late mediastinal uptake) / (early heart uptake early mediastinal uptake) x 100, without considering radioactive decay, and expressed as percentages 28 (Figure 1). Two nuclear physicians analyzed separately the images, with 98% of interobserver agreement, and defined the following as abnormal: WO% > 27% and late HMR ≤ 1.8. 29 The effective radiation dose for the patient, resulting from the administration of 111 MBq/3mCi of 123 I-MIBG was estimated as approximately 4.8 mSv, comparable to one of the phases of myocardial perfusion studies with  99m Tc‑isonitrile. 30 Statistical analysis For this analysis, a sample of 76 patients was calculated to detect a 12% variation in the early or late 123 I-MIBG uptake (HMR), with 5% alpha error and 80% power (CI = 95%) for three groups of patients. Figure 1 – Early (15-minute) and late (180-minute) anterior planar imaging of the chest by 123 I-MIBG scintigraphy, with regions of interest (ROI) positioned on the superior mediastinum between the pulmonary fields and heart. 183