title: Relative effects of propranolol and timolol on ventricular fibrillation threshold and hemodynamics in the dog.
abstract: The relationship between the antifibrillatory and hemodynamic effects of propranolol and timolol was tested in 32 dogs divided into three groups. In closed-chest animals (group 1), the maximal increase of the ventricular fibrillation threshold (VFT) from the control state was 67.3 +/- 22.6% (n = 5, p less than 0.01) for propranolol and 95.8 +/- 18.8% (n = 9, p less than 0.005) for timolol. These effects were paralleled by a decrease in the cardiac index of 34.7 +/- 10.2% (p less than 0.05) and 32.5 +/- 9.4% (p less than 0.02) for propranolol and timolol, respectively. The mean systemic arterial pressure (SAP) also decreased by 25.0 +/- 8.8% (p less than 0.05) and 19.2 +/- 5.1% (p less than 0.01). In open-chest animals (group 2), timolol increased the VFT by 86.6 +/- 27% (n = 5, p less than 0.05) and decreased the cardiac index by 57.3 +/- 6.3% (p less than 0.005) and the mean SAP by 28.5 +/- 2.9% (p less than 0.02). In open-chest animals with stabilized peripheral hemodynamics (group 3), VFT increased by 354 +/- 130% (p less than 0.05) and 437 +/- 144% (p less than 0.05) after the maximal administered doses of propranolol (n = 6) and timolol (n = 7), respectively. These results suggest that the electrophysiologic and hemodynamic effects of beta blockade are parallel and interdependent, with the hemodynamic deterioration markedly blunting the beneficial electrophysiologic effects.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004285:Dogs; D004554:Electric Countershock; D004562:Electrocardiography; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D011433:Propranolol / Q000627:therapeutic use*; D013318:Stroke Volume / Q000187:drug effects; D013999:Timolol / Q000627:therapeutic use*; D014693:Ventricular Fibrillation / Q000188:drug therapy* / Q000503:physiopathology
chemical_list: D013999:Timolol; D011433:Propranolol