title: Critical role of dose in protection by propranolol against ventricular fibrillation in a pig model of acute myocardial ischemia.
abstract: We hypothesized that the antiarrhythmic efficacy of propranolol during acute myocardial ischemia could be dose related. Propranolol was administered in two equally divided doses 30 min before and 10 min after ligation of the anterior descending coronary artery (CAL) in anesthetized open-chest pigs. Only the lowest dose of propranolol, i.e., 0.1 mg/kg intravenously (i.v.) (plasma level 22 +/- 2 ng/ml) decreased the incidence of ventricular fibrillation (VF), i.e. 3 of 12 versus 16 of 20 in control group (p less than 0.01). VF incidence with propranolol 0.5 or 3 mg/kg was 4 of 6 and 8 of 9, respectively (both NS vs. control group). Propranolol 0.1 mg/kg did not change left ventricular (LV) blood flow. Propranolol 3 mg/kg reduced blood flow in the peripheral ischemic myocardium to 13.2 +/- 1.2 versus 19.2 +/- 1.4 ml/100 g/min in control group (p less than 0.01), and in the midischemic zone to 4.4 +/- 0.5 versus 7.0 +/- 0.9 ml/100 g/min in control group (p less than 0.001). Propranolol 0.1 mg/kg prevented a disparity of levels of cyclic AMP from arising between ischemic and non-ischemic myocardium, whereas propranolol 3.0 mg/kg did not. Furthermore, LV mechanical function was suppressed by propranolol 3 mg/kg. Only the lowest dose of propranolol (i.e., 0.1 mg/kg) decreased the incidence of VF in this model.
authors: Department of Medicine, Groote Schuur Hospital, South Africa.
authors: C A
authors: CA
authors: Muller
authors: L H
authors: LH
authors: Opie
authors: M
authors: M
authors: Peisach
authors: C A
authors: CA
authors: Pineda
authors: C W
authors: CW
authors: Hamm
authors: F T
authors: FT
authors: Thandroyen
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000319:Adrenergic beta-Antagonists; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003327:Coronary Disease / Q000188:drug therapy* / Q000503:physiopathology; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D008297:Male; D009206:Myocardium / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D011433:Propranolol / Q000008:administration & dosage / Q000627:therapeutic use*; D013552:Swine; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000517:prevention & control*
chemical_list: D000319:Adrenergic beta-Antagonists; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D011433:Propranolol; D000242:Cyclic AMP