Myocardial responses to acetylstrophanthidin during veratrum alkaloid refractoriness.

Studies were undertaken in the isolated blood perfused dog heart to determine the nature of the myocardial refractoriness induced by veratrum alkaloids. The initial intracoronary injection of cryptenamine acetates (Unitensin) was always associated with an increase in myocardial contractility and a loss of myocardial potassium. Subsequent doses produced refractoriness with respect to both the contractile and potassium responses. Acetylstrophanthidin still produced an inotropic and potassium losing effect duct of the glycoside was potentiated whereas the contractile response was not.