ABSTRACT
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.
Subject(s)
Aging , Digitalis Glycosides/therapeutic use , Isoproterenol/therapeutic use , Myocardial Contraction/drug effects , Adolescent , Adult , Aged , Electrocardiography , Female , Humans , Male , Middle AgedABSTRACT
The baroreceptor sensitivity was estimated in 50 normal controls (Group A) and in 50 diabetics of comparable age (Group B). The technique used was infusion of angiotensin (0.5 microgram/min) and measurement of the bradycardic response resulting from the increase of blood pressure. The slope was used as an index of baroreceptor sensitivity. Diabetics had significantly lower baroreceptor sensitivity and a higher resting heart rate. Sensitivity decreased with age in both groups. The reproducibility of the method was excellent. Deslanoside-C (0.8 mg) significantly increased the baroreceptor sensitivity in 11 normal controls and 9 diabetics. Very low sensitivity was found in 26 diabetics who had no evidence of orthostatic hypotension, neuropathy, or retinopathy. However all 17 patients with the above findings had very low sensitivity.
Subject(s)
Diabetes Mellitus/physiopathology , Digitalis Glycosides/pharmacology , Pressoreceptors/drug effects , Adolescent , Adult , Aged , Angiotensin II/pharmacology , Blood Pressure/drug effects , Deslanoside/pharmacology , Female , Heart Rate/drug effects , Humans , Male , Middle AgedABSTRACT
In 26 normal volunteers, increase in heart rate from mean 73-94 +/- 1-97 to 103-61 +/- 2-72/min, by either intravenous atropine administration or rapid right atrial pacing, produced definite changes in the uncorrected systolic time intervals. As expected, total electromechanical systole (QS2) and left ventricular ejection time (LVET) were shortened, while the pre-ejection period (PEP) was unaffected. There was a consistent and significant increase of the PEP/LVET ratio (P less than 0-001). It is postulated that when this ratio is taken to express left ventricular contractility, it should probably be corrected for heart rate. Appropriate regression equations for such a correction were calculated (PEP/LVET=0-249 + 0-0168 HR).
