Aging is known to cause changes in autonomic system function; in order to evaluate the ability of the electrical/electromechanical systole ratio in monitoring the effects of beta-adrenergic stimulation on the heart, the influences of aging and beta-blockade on ratio changes induced by isometric exercise (75% of maximal voluntary contraction) were studied. Study population was composed of 45 healthy volunteers (23 males and 22 females, aged 16 to 84) and was divided in three groups: group 1 (mean age 21 ± 3 years), group 2 (mean age 43 ± 10 years) and group 3 (mean age 74 ± 6). Ten subjects (mean age 35 ± 7) repeated the test after propranolol administration. Isometric exercise caused significant increase in heart rate, systolic and diastolic blood pressure in all 3 groups. Ratio values increased both in groups 1 and 2, but significantly only in group 1. No change in ratio was observed in group 3. Ratio changes induced by isometric exercise were significantly smaller in group 3 as compared to group 1 and correlated inversely with age. Propranolol administration prevented such ratio increase induced by isometric exercise. These data show that exercise-induced changes in the ratio are affected by aging, which causes a decrease in beta-receptorial sensitivity. However, the wide interindividual variability of the handgrip-induced ratio changes limits the utilization of this index as a parameter of sympathetic stimulation during this particular type of stress.
|Number of pages||9|
|Journal||Journal of Applied Cardiology|
|Publication status||Published - 1988|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine