Dobutamine in left heart failure after acute myocardial infarction

Dobutamine, a new positive inotropic drug, was given as i.v. infusion at a rate of 2.5--7.5 micrograms/kg/min to nine male patients with a moderately severe left heart failure. The patients were treated in our CCU for acute myocardial infarction (AMI) and had PEP/LVET above 0.40 on routine registrations of systolic time intervals, PEP (preejection phase), PEPI (PEP corrected for heart rate), LVET (left ventricular ejection time) and LVETI (LVET corrected for heart rate). Dobutamine increased contractility, measured as shortening of PEP and PEPI, and also increased ejection fraction, measured as PEP/LVET. Concomitantly, heart rate increased significantly but no changes were noted in systolic or diastolic BPs. The positive inotropic effect of dobutamine was thus accompanied by a positive chronotropic effect, which limits the usefulness of the drug in patients with recent AMI.