[Comparative study between dobutamine and other catecholamines in their effects on the cardiac contraction and rhythm...

Dobutamine (DOB) showed a dose dependent positive introphic effect on the right ventricular muscle of vagotomized Beagle dogs under pentobarbital anesthesia. Positve inotropic effects of other catecholamines (CA) decreased in the following order; isoproterenol (Iso, 115) greater than norepinephrine (NE, 15) greater than DOB (1) greater than dopamine (DA, 0.36). Brachiocephalic arterial flow was also increased by DOB with a positive inotropic effect in the right ventricular muscle. Though the positive inotropic effect of DOB was slightly decreased by pretreatment with phenoxybenzamine, such was almost completely antagonized by propranolol. Contractions of isolated cat papillary muscle driven by electrical stimulation (12 beats/min) were increased by CA in the following order; Iso (17) greater than NE (3) greater than epinephrine (2.5) greater than DOB (1) greater than DA (1 greater than). Activity of DOB to induce spontaneous contractions of papillary muscle was weakest among these CA. To determine the arrhythmogenic effect of these CA, coronary ligated Beagle dogs were employed, in which the anterior descending branch of the left coronary artery was ligated. Arrhythmogenic activity of DOB was weaker than other CA employed both in early stages and 48 hr after coronary ligation. DOB shows good potential for treating acute cardiac insufficiency and cardiogenic shock, as effects on heart rate and blood pressure are weaker.