Effects of S-dobutamine on ischemic myocardium caused by coronary artery narrowing.

Cardiovascular effects of S-dobutamine were compared with effects of vehicle and other catecholamines in dogs during and after 3 days of approximately 90% ligation of the left anterior descending coronary artery (LAD). Twenty-four hours after LAD ligation, dogs infused with S-dobutamine (2.5 micrograms/kg/min intravenously, i.v.) maintained systolic blood pressure (SBP 149 +/- 6 mm Hg), diastolic blood pressure (DBP 100 +/- 6 mm Hg), and aortic dP/dt60 (2.8 +/- 0.2 s-1), with no significant changes from preligation values. In comparison, saline-treated dogs showed decreases in arterial BP and contractility: SBP 121 +/- 4 mm Hg; DBP 85 +/- 3 mm Hg; and aortic dP/dt60 was 1.9 +/- 0.1 s-1. S-Dobutamine-infused dogs had a heart rate (HR) of 148 +/- 5 beats/min with 44 +/- 14 beats/min premature ventricular contractions (PVCs), whereas dogs infused with saline, R-dobutamine, dopamine, norepinephrine (NE), or isoproterenol (ISO) all displayed a significantly greater number of PVCs at 24 h. Myocardial necrosis was limited by S-dobutamine treatment (2.5 micrograms/kg/min i.v. for 54 h). As demonstrated by histologic examination, S-dobutamine ameliorated the effects of ischemia as compared with vehicle, R-dobutamine, dopamine, hexamethonium, NE, or ISO. Myocardial tissue electrolytes, quantified 72 h after LAD ligation, were maintained by S-dobutamine-infused dogs in all sections of left ventricle (LV); but in saline-treated dogs, Ca2+ increased eightfold, Na+ increased twofold, and both K+ and Mg2+ decreased 50% in tissue "at risk" as compared with tissues "not at risk." Coronary nutrient blood flow (CNBF) to myocardial capillary vessels was calculated by radiolabeled microspheres 2 h after LAD ligation. As compared with CNBF in untreated hearts, endocardial CNBF in hearts receiving S-dobutamine (5 micrograms/kg/min i.v.) increased from 26 +/- 8 to 49 +/- 15 ml/min/100 g in tissue at risk, from 102 +/- 26 to 217 +/- 50 in "border zone," and from 133 +/- 13 to 215 +/- 41 in tissue not at risk. CNBF values in animals receiving vehicle infusion were not significantly different from CNBF values measured after ligation only. The S-enantiomer of dobutamine, infused in dogs for 54 h after coronary artery ligation, maintained cardiac performance, electrolyte balance, and myocardial cellular viability and reduced incidences of arrhythmias through its ability to increase CNBF without increasing HR.