Patients with chronic Chagas disease have a higher prevalence of premature ventricular contraction (PVC) because of immunoinflammatory response magnified by the increased oxidative stress. Thus, the sequential treatment with benznidazole (BZN) and antioxidants can reduce the prevalence of PVC. We wish to establish whether the etiological treatment of Chagas disease followed by supplementation with the antioxidant vitamins E and C decreases the prevalence of PVC in these patients. A sample of 41 patients with chronic Chagas disease at different stages of the heart disease was selected for the treatment against the causative agent using BZN (5 mg·kg·d, minimum dose 300 mg daily) for 2 months followed by supplementation with antioxidants such as vitamins E (800 UI/d) and C (500 mg/d) for 6 months. The prevalence of PVC was observed by conducting 24-hour Holter. To evaluate the oxidative status of the patients, serum markers of oxidative stress like glutathione peroxidase, superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase were measured, and also reduced glutathione, vitamin E, and markers of tissue damage like thiobarbituric acid reactive substances and protein carbonyl. A decrease in the prevalence of PVC in patients with advanced Chagas heart disease was observed (5391 vs. 1185, P = 0.0068). This reduction was followed by decrease of serum markers of oxidative stress. In patients with a lower degree of cardiac damage, the reduction on prevalence of PVC was not significant. The etiological treatment with BZN followed by supplementation with antioxidant vitamins E and C reduces episodes of PVC in patients with severe Chagas heart disease.

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Background: Sudden death is the leading cause of death in Chagas' disease, affecting patients even in the early stages of the disease. The impairment of the autonomic nervous system in this disease has been recognized, as well as its potential as a trigger for malignant arrhythmias when associated with structural or metabolic changes.

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Patients with intermediate probability of coronary disease are a diagnostic challenge and it is precisely in this population where the degree of uncertainty is greater that the diagnostic tests have their greater applicability. However, according to the current definition, subjecting to tests a population with a disease probability between 10 and 90% can generate unnecessary tests and misleading results. Knowing the characteristics of each test, as well as risks and benefits of drug treatment for coronary disease and combining this information through diagnostic thresholds brings a new perspective to decision making. To review the origin of the currently recommended concepts of intermediate probability and to determine the thresholds for diagnosis and treatment of noninvasive tests and, based on them, propose a new concept of intermediate probability of coronary disease. Through the bibliographic review, meta-analyses were extracted in which data of sensitivity, specificity, positive and negative likelihood ratio, risks and benefits of the tests and treatment were provided. Using an algorithm developed by Pauker et al. it was possible to obtain the diagnostic and treatment thresholds adjusted for each tests in question. The concept of intermediate probability of coronary disease is quite broad, ranging, according to the authors, between 10 and 90%, 1 and 92%, 15 and 85%, with different rationale. Considering the discriminatory power of each test, risks and treatment benefits, the diagnostic and treatment thresholds were defined for exercise testing (22-58%), eco-stress (10-72%), myocardial scintigraphy (12-80%), nuclear magnetic resonance (16-80%) and coronary angiotomography (6.7-81%). The decision to submit to diagnostic tests should be individualized, taking into account the diagnostic and treatment thresholds of each method in question.