Hemodynamics During the Acute Phase of Myocardial Damage Caused by Isoproterenol

One to three days after two consecutive subcutaneous injections of 40 mg/kg isoproterenol were given to male rats, severe histological changes occurred in the myocardium. Blood pressure, cardiac output, and work of these rats did not differ from normal. During polyvinylpyrrolidone infusion, normal rats raised their cardiac output to about three times the preinfusion value, while only a slight increase took place in the isoproterenol-treated rats. The difference was less marked during pitressin and norepinephrine infusion. It is concluded that during the acute damage of the myocardium by isoproterenol, the functional capacity of the heart is greatly reduced.