Pathogenesis and Pathology of Chagas' Chronic Myocarditis

Chronic chagasic cardiomyopathy (CCC) is the most serious manifestation of the chronic phase of Chagas’ disease and constitutes the most common type of chronic myocarditis in the world (Guerri-Guttenberg, et al., 2008, Milei, et al., 1996a, Milei, et al., 2009, Milei, et al., 1992a, Storino, et al., 1992). Chagas’ disease, a chronic illness caused by the flagellate parasite Trypanosoma cruzi (T. cruzi), was first described in 1909 by the Brazilian physician Carlos Chagas (Chagas C, 1909). The insect vectors of the disease are present throughout most of South and Central America, and their zone of distribution extends across the southern United States (Rassi, et al., 2010). It was estimated by year 2000, that in endemic areas 40 million people were considered to be at risk of infection, being 20 million already infected. Every year near 200,000 new cases are expected to happen, and 21,000 deaths per year occur (WHO, 2005). Although always considered to be confined to Latin America, due to migratory movements from endemic countries to Europe and North America, Chagas’ disease is being detected more frequently in developed countries. Europe is estimated to have from 24,001 to 38,708 (lower or upper limit of estimate, respectively) immigrants with T. cruzi infection (GuerriGuttenberg, et al., 2008). In the United States, six autochthonous cases, five transfusion related cases and five transplant related cases have been reported, but migratory movements still remain the main source of Chagas’ disease. It has been estimated that around 89,221 to 693,302 infected Latin Americans migrated to the United States in the period 1981 to 2005 (Milei, et al., 2009). Two phases of the disease can be distinguished: (1) acute phase, with transiently high concentration of parasites in tissue and blood, nonspecific symptoms, and a 5% myocarditis incidence, lasting 4 – 8 weeks; and (2) chronic phase, lasting lifelong. Chronic phase can be presented as indeterminate form, characterized by lack of symptoms and normal ECG and normal radiographic examination of the chest, esophagus and colon. Approximately 60 – 70% of patients remain in this form for the rest of their lives. Only 20-40% of infected individuals, 10-30 years after the original acute infection, will develop cardiac, digestive or mixed form of the disease, characterized by the appearance of megavicera (dilated cardiomyopathy, megaesophagus and/or megacolon). It poses a substantial public health burden due to high morbidity and mortality (Milei, et al., 2009, Rassi, et al., 2000, Rassi, et al., 2010).