 The Selenium treatment and Chagasic Cardiopathy STCC trial is double-blind, placebo controlled, randomized in 130 chagasic patients at the chronic phase following the inclusion criteria of a altered ECHO LVEF between 0,35 and 45 , b age between 20 and 65 years, c randomly divided in two groups: Placebo n65 and Se n65. Patients of Se group will intake diary 100 μg Se as sodium selenite for 12 months. The primary endpoint is the reduction of 50 in the progression rate of heart dysfunction, and the secondary endpoint is a partial or total reversion in electrocardiography alterations. 