Effects of age and hypertension on adrenoceptor-sensitivity evaluated with CD25 and QT/QS2

Background. We studied the effects of age and hypertension on responses to chronotropic dose (CD25) and standinginduced changes in the ratio of electrical systole (QT) to electromechanical systole (QS2) in order to identify their role on beta adrenoceptor sensitivity and to verify the value of QT/QS2 ratio as a noninvasive parameter of beta-adrenoceptor sensitivity. Methods. We enrolled 33 normal subjects and 37 hypertensive patients (WHO stage I and II) (age range 21-82 years). Results. CD25 was significantly age-related in normotensive and hypertensive subjects, whereas standing-induced QT/QS2 changes were age-related in normotensive subjects only When we divided subjects into three age groups, betaadrenoceptor sensitivity was found to be lower in hypertensives than normotensives in the two groups under age 60, but was not affected in those over age 60. This suggests that hypertension influences beta-adrenoceptor sensitivity in younger subjects, but not in elderly patients, whose beta-adrenoceptor sensitivity is already reduced. Conclusions. CD25 does not predict standing-induced QT/QS2 ratio changes; therefore, during autonomic stimulation, QT/QS2 ratio seems not to be significantly related to beta adrenergic sensitivity.