ABC | Volume 110, Nº2, February 2018

Original Article The Presence and Extension of Myocardial Fibrosis in the Undetermined Form of Chagas’ Disease: A Study Using Magnetic Resonance Marcia Maria Noya-Rabelo, 1,2 Carolina The Macedo, 1,3 Ticiana Larocca, 3 Admilson Machado, 2 Thais Pacheco, 2 Jorge Torreão, 1 Bruno Solano de Freitas Souza, 3 Milena B. P. Soares, 3 Ricardo Ribeiro-dos-Santos, 3 Luis Claudio Lemos Correia, 1,2 Hospital São Rafael - Fundação Monte Tabor; 1 Escola Bahiana de Medicina e Saúde Pública; 2 Centro de Biotecnologia e Terapia Celular, 3 Salvador, BA – Brazil Mailing Address: Marcia Maria Noya Rabelo • Rua Queira Deus Cond. Rio Joanes, Lt B13. Postal Code 42-713-480, Portão, Lauro de Freitas, BA – Brazil E-mail: marcianoya@cardiol.br , marcianoya@gmail.com Manuscript received May 03, 2017, revised manuscript August 17, 2017, accepted August 21, 2017 DOI: 10.5935/abc.20180016 Abstract Background: Previous data has shown that patients in the indeterminate form of Chagas disease may present myocardial fibrosis as shown on through magnetic resonance imaging (MRI). However, there is little information available regarding the degree of severity of myocardial fibrosis in these individuals. This variable has the potential to predict the evolution of Chagas’ disease into its cardiac form. Objectives: To describe the frequency and extent of myocardial fibrosis evaluated using an MRI in patients in the indeterminate form, and to compare it with other forms of the disease. Methods: Patients were admitted one after another. Their clinical history was collected and they were submitted to laboratory exams and an MRI. Results: Sixty-one patients with Chagas’ disease, with an average age of 58 ± 9 years old, 17 patients in the indeterminate form, 16 in the cardiac form without left ventricular (LV) dysfunction and 28 in the cardiac form with LV dysfunction were studied. P <0.05 was considered to be statistically significant. Late enhancement was detected in 37 patients (64%). Myocardial fibrosis was identified in 6 individuals in indeterminate form (41%; 95% CI 23-66) in a proportion similar to that observed in cardiac form without LV dysfunction (44%); p = 1.0. Among the individuals with fibrosis, the total area of the affected myocardium was 4.1% (IIQ: 2.1 - 10.7) in the indeterminate form versus 2.3% (IIQ: 1-5) in the cardiac form without LV (p = 0.18). The left ventricular fraction ejection in subjects in the indeterminate form was similar to that of the individuals in the cardiac form without ventricular dysfunction (p = 0.09). Conclusion: The presence of fibrosis in the indeterminate form of Chagas’ disease has a frequency and extension similar to that of in the cardiac form without dysfunction, suggesting that the former is part of a subclinical disease spectrum, rather than lacking cardiac involvement. (Arq Bras Cardiol. 2018; 110(2):124-131) Keywords: Chagas Disease; Chagas Cardiomyopathy; Fibrosis; Magnetic Resonance Imaging. Introduction Chagas’ disease is a potentially debilitating endemic problem in Latin American countries and has led to an estimated loss of 750,000 years of productive life. 1-5 Three stages of Chagas’ disease are recognized: acute, indeterminate and chronic. 4,6 After the acute phase, about two-thirds of infected patients remain in the indeterminate form, which is characterized by the absence of significant clinical, electrocardiographic or radiological manifestations. However, the disease does not manifest itself in these patients and one-third of them progress to some type of cardiac and/or digestive manifestation, and thus are reclassified as chronic. 7 Identifying the indeterminate patients that are prone to progress to the chronic form serve as a basis for the research of preventive strategies and a better understanding of the pathological processes that lead to this evolution. However, there are no predictive markers or models capable of estimating the risk of this change. As such, several researchers consider myocardial fibrosis to be a possible substrate for the development and progression of ventricular dysfunction, arrhythmia, and death. 3,8-10 The etiopathogenic process that promotes fibrosis involves a multifactorial relationship between the aspects related to the etiologic agent and those related to the host 2,11-14 The advent of cardiovascular magnetic resonance imaging (CMR), with the use of the late enhancement technique allows for the identification of myocardial fibrosis. Furthermore, it has a gold standard rating with a close anatomopathological correlation. 15 There is evidence that CMR is able to provide images with high spatial resolution and a high level accuracy in assessing ventricular function. 16 Previous data have shown that even patients with the indeterminate form may have myocardial fibrosis 124