Confirming the Diagnosis of Chagas Disease
Confirmatory testing should be sent to the CDC. The diagnosis of Chagas disease relies on serologic analyses, and no commercially available test is 100% sensitive or specific for the disease. Therefore, the diagnosis is not established until a second assay, either using a different method (eg, TESA blot [trypomastigote excreted-secreted antigens] or immunofluorescence assay) or a different antigen (enzyme-linked immunosorbent assay), is positive. The gold standard for the diagnosis of Chagas disease is the presence of parasite in either a blood or biopsy specimen (Figure 2). Parasitemia is common in acute infection and in reactivation disease (ie, chemical or disease-induced immunosuppression), but much rarer in chronic disease, so the absence of parasites does not rule out Chagas disease.
This patient has Chagas cardiomyopathy (defined by positive serology and an abnormal ECG), the end result of a subacute myocarditis caused by T cruzi infection. The infection generally occurs in childhood, and up to 25% of new cases are caused by maternal-fetal transmission. After an initial acute illness (rarely remembered by the patient), virtually all patients pass into the "indeterminate phase" of the disease. This is characterized by positive serologic testing but no end-organ damage is yet apparent. In time, 20%-30% of infected persons will develop cardiac manifestations, ranging from abnormal ECGs to stroke, arrhythmias, and heart failure.
Echocardiography findings in Chagas cardiomyopathy range from normal structure and function in patients with indeterminate phase disease to focal apical aneurysms, scarring/regional wall motion abnormalities (inferolateral wall in particular), and dilated cardiomyopathies (Figure 3).
Cardiac MRI is a reasonable, albeit expensive, tool to risk-stratify patients with Chagas cardiomyopathy. Recent data have shown a strong relationship between the level of late gadolinium enhancement and mortality, so MRI may help in deciding whether the patient should be offered defibrillator therapy.
Chagas disease is also highly arrhythmogenic, with both bradyarrhythmias and tachyarrhythmias resulting from focal scarring.
Treatment of Chagas Disease
Medical treatment of Chagas comprises benznidazole 5-7 mg/kg/day in divided doses for 60 days; this is the only approved agent at this time. However, treatment with antiparasitic drugs is controversial. Few randomized trials have been conducted to date. One trial of benznidazole (BENEFIT) randomly assigned patients with Chagas cardiomyopathy to benznidazole therapy or placebo, and evaluated the rates of hard cardiac endpoints at 5 years. Despite a significant reduction in polymerase chain reaction positivity in the treated group, no benefits in cardiac endpoints were seen.
Treatment is strongly advised in women of childbearing age. Antiparasitic therapy before pregnancy has been shown to reduce maternal-fetal transmission of the infection. Infants and children have the highest rates of cure if treated as soon as the diagnosis is made.
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Cite this: Chagas Cardiomyopathy: The Disease You Might Not Think Of - Medscape - Apr 16, 2019.