Plasma concentrations and haemodynamic effects of d-sotalol after beta-blockade in dogs

This study was designed to investigate the haemodynamic effects of d-sotalol at plasma concentrations producing class III antiarrhythmic effects. d-Sotalol 1, 4 and 10 mg/kg intravenously was given after beta-blockade (propranolol 0.25 mg/kg intravenously) to seven pentobarbital anaesthetized dogs. Left ventricular (LV) systolic and end-diastolic pressures, LV dP/dtmax, mean aortic pressure, stroke volume, cardiac output and total peripheral resistance were not significantly changed by d-sotalol. There was a linear correlation between the dose of d-sotalol infused and the plasma concentration of d-sotalol obtained. Heart rate decreased and QT-time increased with increasing plasma concentrations of d-sotalol, whereas the QRS-width did not change. There was a linear correlation between the decrease in heart rate and the increase in QT-time, and between the plasma concentration of d-sotalol and increase in QT-time. In conclusion, the study indicates that after beta-blockade, d-sotalol has no cardiodepressive effects at concentrations that prolong repolarization.