Effects of long term metoprolol administration on the electrocardiogram of rats infected with T cruzi

Study objective – The aim of the study was to evaluate the role of β receptor antagonists in the evolution of experimental Chagas’ disease. Design – Rats were infected with T cruzi, 2000 parasites·g−1 body weight, soon after weaning. One group was then given metoprolol, 100 mg·kg−1·d−1, in drinking water. A comparison group received no metoprolol. Two control groups of non-infected rats were also studied, one with and one without metoprolol in the same dose. Subjects – Adult male albino rats were used: 144 were infected with T cruzi and received metoprolol (group IM), 137 were infected and received no metoprolol (group IW), 46 non-infected rats received metoprolol (group CM), and 43 non-infected rats did not receive metoprolol (group CW). Measurements and main results – 30 d after infection, resting ECG was performed in all surviving rats. (There were 63 deaths in the infected groups and none in the non-infected groups.) Abnormal ECG was found in 20/81 infected rats in group IM and in 30/74 in group IW (p