Thyroid hormone treatment improved the response to maximum exercise test and preserved the ventricular geometry in myocardial infarcted rats.

NEW FINDINGS What is the central question of this study? This study sought to evaluate whether thyroid hormone treatment given after myocardial infarction could preserve the left ventricular function, treadmill exercise performance, and improve parameters of oxidative stress in the right ventricle and lungs of Wistar rats. What is the main finding and its importance? The main contribution of this study is the finding that thyroid hormone treatment improved the performance of the maximum exercise test in infarcted rats and induced effects in the heart and lungs that were similar to those observed with exercise training. This suggests a significant value of thyroid hormones for preserving exercise tolerance after myocardial infarction. ABSTRACT Left ventricle myocardial infarction (MI) provokes damage in the heart and in other tissues, such as right ventricle (RV) and lungs. The present study elucidated whether thyroid hormones treatment (THT) may present positive effects in heart and lungs after MI, and whether these effects are similar to those of exercise training (ET) or not. Male Wistar rats were divided into four groups: SHAM operated (SHAM); infarcted (MI); infarcted + exercise training (MIE); and infarcted + thyroid hormones (MIH). Maximum exercise test, left ventricle (LV) echocardiography and histology and oxidative stress in the right ventricle and lung were evaluated. THT and ET both reduced LV dilatation and end-diastolic wall stress indexes to a similar extent. MI accentuated the content of macrophages and inflammatory infiltrate in the lungs, which were partially prevented in MIH and MIE groups. THT and ET presented similar effects in the heart and lungs, and both improved the performance of maximum exercise test in infarcted animals. This article is protected by copyright. All rights reserved.