the effect of phenoxybenzamine on myocardial contractility in dogs

the cardiac action of phenoxybenzamine (dibenzyline) was studiedusing the maximum rate of pressure rise in the left ventricle as a measure of myocardial contractility. cardiac function was assessed by increasing the pressure load on the heart and measuring contractility as reflected by dp/dt. dibenzyline was found to change the cardiac response to pressure load. the rate of pressure increase in the left ventricle at any specified left ventricular end diastolic pressure was found to be greater after the administration of dibenzyline. similarly, the rate of pressure development was fo und to be greater at any specified peak ventricular pressure after dibenzyline administ ration. these changes were analyzed statistically and were found to be significant. the mechanism producing these changes is not known.