Comparison of the inotropic action of digitalis and isoproterenol in younger and older individuals.

The positive inotropic effects of digitalis (deslanoside C, 1.2 mg. intravenously) and isoproterenol (2 microgram/minute intravenously) were compared in two groups of younger and older individuals using the systolic time interval method. Both groups responded in a completely comparable way to deslanoside C. However, after isoproterenol administration, the LVET of the older group was significantly shortened. Consequently, the PEP/LVET ratio did not change significantly. This difference is attributed to a lesser increase of the stroke volume in the older group.