The usefulness of the resting electrocardiogram for characterizing acute Chagas' heart disease in the rat.

The present experiment was undertaken to characterize the resting electrocardiogram of rats in the acute stage of experimental T. cruzi infection. One-hundred-and-eighty-seven newly-weaned male albino rats were infected intraperitoneally with 1000 parasites/g body weight. Thirty-two similar but non-infected rats served as controls. Groups of eight randomly chosen rats were killed on day 8, and on days 15, 18, 22, 25 and 29 after infection. Groups of 8 control rats were killed on days 8, 15 and 22. Electrocardiographic changes were observed in 25 of 48 (52%) infected rats. P wave abnormalities indicating atrial chamber dilatation, QRS axis deviation, QRS complex changes compatible with left ventricular hypertrophy or myocardial damage, increased PR interval and ventricular repolarization alteration were detected in 24, 27, 18, 10, and 6% of infected rats, respectively. A mononuclear cell infiltrate and pseudocysts of amastigote forms of T. cruzi were found in 91, and 56% of infected animals, respectively. The sensitivity and the positive predictive value of the electrocardiographic changes were 66, 91, and 96%, respectively. Thus, the resting electrocardiogram is a reliable method for detecting myocardial lesions in the rat with acute Chagas' heart disease.