ABC | Volume 114, Nº2, February 2020

Update Update of the Brazilian Guideline on Nuclear Cardiology – 2020 Arq Bras Cardiol. 2020; 114(2):325-429 Takotsubo syndrome, and cardiac involvement due to systemic conditions, as in Parkinson’s disease. Generally speaking, this exam has been established to have an effective capacity for risk stratification of patients with the previously described conditions, but the utility of this information in improving clinical results of patients has not yet been demonstrated. 331 13.3.1. Heart Failure In this condition, altered cardiac adrenergic innervation is strongly correlated with mortality, and reduced cardiac uptake of MIBG- 123 I (late HMR) confers independent and additional long-term prognostic value to other established markers, such as LVEF and B-natriuretic peptide (BNP). 334-336 Some studies have demonstrated that abnormalities in cardiac uptake of MIBG- 123 I may be predictive of increased risk of ventricular arrhythmia and sudden cardiac death, 322,337 with attempts to standardize the procedure for the sake of routine clinical application. 328-330 Cardiac scintigraphy with MIBG- 123 I has been approved for use in clinical practice in cardiology since 1992 in Japan, 338 and it is considered a class I indication for evaluation of prognosis and severity of HF, with level of evidence B (Table 31) . 338 Studies with higher numbers of patients have recently been published in Europe and the USA. The AdreView Myocardial Imaging for Risk Evaluation in Heart Failure (ADMIRE-HF) 336 multicenter, prospective, international study involving the use of MIBG- 123 I in HF independently validated the prognostic value of cardiac scintigraphy with MIBG- 123 I for the evaluation of patients with chronic HF. 337 They included 961 patients with HF, NYHA HF functional class II–III, and LVEF ≤ 35%, undergoing cardiac scintigraphy with MIBG- 123 I, f ollowed for an average of 17 months. Approximately 25% of patients (n = 237) had cardiac events, with approximately 70% of the first events being progression of chronic HF; 20% potentially lethal arrhythmic events (sustained VT > 30 seconds, heart arrest with cardiac arrest with resuscitation and appropriate ICD firing; and approximately 10% cardiac death; with 22% of patients presenting multiple events. Lower risks of the compound outcome were observed in patients with HMR ≥ 1.60 versus HMR < 1.60 (38%; hazard ratio: 0.40; p < 0.001) with a highly significant risk ratio for each individual component of the primary compound outcome evaluated. It is worth highlighting that total mortality over 2 years was around 5 times higher (16.1% versus 3.0%) in patients with late HMR < 1.60 compared to those with HMR ≥ 1.60, respectively. 337 Considering this information, the FDA has approved MIBG- 123 I ( AdreView R ), in 2013, for evaluation of cardiac sympathetic innervation in patients with New York Heart Association (NYHA) HF class II-III and LVEF < 35%. 326 In addition to prognostic evaluation of HF, 333-339 other applications which stand out include the following: evaluation of therapeutic response to medication; 340,341 indication and evaluation of response to cardiac resynchronization therapy (CRT); 342 indication for implant and explant of mechanical left ventricular assist device, 343,344 and implantable cardioverter defibrillator (ICD); and evaluation of reinnervation following cardiac transplant. 345 Late HMR of MIBG- 123 I in patients with severe chronic HF, in accordance with traditional classification criteria (LVEF, BNP, functional class), may help reclassify patients into a category of lower risk for events. Patients with late HMR ≥ 1.6 (even with very low LVEF and elevated BNP) have a low probability of severe cardiac events during a period of up to 2 years. This information may lead to changes in treatment. 331 This marker may, also, help refine indication criteria for high-cost invasive therapies for HF, such as CRT 342,346 and ICD implant. 347,348 A Brazilian study carried out by Nishioka et al. 342 has shown that HMR was the only independent predictor of therapy response. Patients with HMR < 1.36 had a lower chance of benefitting from CRT, suggesting that these patients with rather elevated cardiac sympathetic activity have terminal HF. 342,346 The autonomic nervous system plays an important role in cardiac arrhythmias . Scintigraphy with MIBG- 123 I has the potential to select patients for ICD implant more accurately, in addition to identifying those at higher risks of sudden cardiac death, who would not be selected in accordance with current guidelines. Arora et al., 347 in a pilot study of 17 patients with advanced chronic HF and ICD, divided patients into groups according to the presence or absence of previous ICD firing. In cases with late HMR of MIBG- 123 I < 1.54, they observed a higher frequency of ICD firing and a positive predictive value of 71%, at the same time that increased HMR was observed to have a NPV of 83%. The etiology of HF is frequently classified as ischemic (I) and non-ischemic (NI). Although the physiopathology and the initial lesion are different, investigation studies have suggested that, as the disease progresses, autonomic cardiac abnormalities are characteristic and common, regardless of etiology. Cardiac scintigraphy with MIBG- 123 Ithus continues to be a strong prognostic marker. Wakabayashi et al. 349 showed that, for both groups, late HMR was the strongest independent predictive factor for sudden cardiac death, although the cutoff points for HMR index values were different, namely 1.50 for ischemic cardiomyopathy and 2.02 for non-ischemic cardiomyopathy. For patients with LVEF < 40% and late HMR lower than the identified cutoff values, the rate of cardiac death was higher in the ischemic group (18.2% annually) than in the non-ischemic group (11.9% annually). 13.3.2. Ventricular Arrhythmia Sudden cardiac death continues to be one of the leading causes of death worldwide. Scarring and/or non- revascularized/ischemic myocardium provide important substrates for the occurrence of potentially lethal ventricular arrhythmias. 350 Furthermore, the presence of clinical HF Table 31 – Recommendations for cardiac scintigraphy with MIBG- 123 I in accordance with the Japanese Circulation Society Guidelines 339 Indication Class of recommendation Level of evidence Evaluation of severity and prognosis of patients with heart failure (HF) I B Evaluation of the effects of HF treatment IIa C Arrhythmogenic disease IIb C 401