The efficacy of isoproterenol on quinidine induced torsade de pointes.

The efficacy of isoproterenol for torsade de pointes (TdP) was evaluated in 60 dogs. TdP was induced in 34 of 60 dogs (56.7%) after the administration of quinidine sulfate (30 mg/kg). The electrophysiologic effect of isoproterenol (0.5 micrograms/min) was studied in 9 dogs with quinidine induced TdP. Isoproterenol significantly shortened basic cycle length, corrected QT interval, effective refractory period (ERP) and dispersion of ERP and increased ERP/QT. Isoproterenol prevented the occurrence of TdP in all dogs. These findings suggest that isoproterenol decreases the dispersion of ventricular refractoriness and may be useful in the treatment of drug induced TdP.