RESISTANCE TO LEFT-VENTRICULAR OUTFLOW STUDIED IN ANESTHETIZED DOGS

A simple method is proposed to determine resistance to left ventricula r output from the evaluation of a parameter Z, given by the ratio of p eak systolic pressure and the corresponding instantaneous blood flow. The method, derived from the basic equation of the Windkessel model, i s applied to analyze pressure and flow data measured in the ascending aorta of anesthetized dogs. The Z values obtained in this way are foun d to be closely related to resistance calculated from the ratio of mea n aortic pressure and mean flow over the cardiac cycle. Effects of abr upt changes of resistance obtained by removing an aortic constriction are also analyzed according to the same basic Windkessel equation and the results show the same close relationship to resistance.