Effects of detraining on cardiovascular and autonomic functions of myocardial infarcted rats: impact on mortality rate

Abstract

Impairments on left ventricular function, as well as neurohumoral changes are associated with high mortality rates in patients after myocardial infarction (MI). The evidenced acute and chronic benefits of exercise training (ET) on the cardiovascular, metabolic and autonomic parameters have led many investigators to suggest that ET is an important tool to the management of coronary artery disease and after MI patients. However, the effects of the cessation of ET on the hemodynamic aspects, autonomic function and baroreflex sensitivity, as well as in the mortality rate, remains poorly studied. Male Wistar rats (230 - 260g) from the Animal House of the University Sao Judas Tadeu will be used. In order to quantify the MI area, echocardiographic evaluation will be performed 2 days after MI surgery and after ET protocol. The animals will be submitted to an aerobic ET protocol on a treadmill with progressive speed and load, for 90 days (5 days per week, 50 to 70% of the maximum speed obtained in the effort test). After ET period, arteries and veins will be catheterized for hemodynamic, autonomic modulation and baroreflex sensitivity evaluations. In the untrained animals, these evaluations will be performed 30 days after ET cessation. Mortality evaluation will be started after the MI surgery recovery. The results will be analyzed using analysis of variance (ANOVA) followed by post-hoc Student-Newman-Keuls test, and significance level established at p <0.05.