BENEFIT: Evaluation of the Use of Antiparasital Drug (Benznidazole) in the Treatment of Chronic Chagas' Disease

Inclusion Criteria: * Consenting patients (between 18 and 75 years of age) with serological evidence of Chagas infection (any combination of 2 positive tests) and that have one or more of the following: * Abnormal electrocardiogram with at least two components (complete RBBB or LBBB; left anterior or posterior fascicular block; ventricular premature beat; first degree atrioventricular \[AV\] block; Mobitz type I AV block; sinus bradycardia; primary ST-T changes; abnormal Q waves; low voltage QRS; or atrial fibrillation); * Abnormal ECG (Mobitz type II, advanced or third degree AV block); * Increased cardiothoracic ratio (\> 0.50); * Complex ventricular arrythmias on 24 hour ambulatory ECG monitoring; * Evidence of regional wall motion abnormality or reduced global left ventricular systolic function or increased left ventricular and diastolic diameter on 2D-Echo. Exclusion Criteria: Patients will be excluded if having: * NYHA heart failure class IV or decompensated heart failure * Evidence of concomitant coronary artery disease (CAD) or other etiology of dilated cardiomyopathy * Previous treatment with antitrypanosomal agents or an accepted indication for antiparasitic therapy * Inability to comply with follow-up visits * History of severe alcohol abuse within 2 years * Known chronic renal or hepatic insufficiency or hepatic insufficiency * Pregnancy or breast feeding * Megaesophagus with swallowing impairment * Other severe disease significantly curtailing life expectancy