Cardiac inhibitory response to alpha stimulation is blunted in young patients with essential hypertension.

A decrease in cardiovascular baroreceptor responsiveness occurs with aging. Similarly, subjects with systemic hypertension exhibit abnormal baroreceptor function. The age-related changes in cardiovascular response to the α-agonist phenylephrine in subjects with essential hypertension (HT) have not been studied. We studied 32 normotensive subjects aged between 21 and 73 yrs, and 25 patients with mild to moderate HT aged between 30 and 64 yrs. Phenylephrine was infused in incremental doses of 0.4 to 1.6 μg/kg/min and cardiac function was measured by echo. Changes in parameters at 1.2 μg/kg/min infusion rate for young normotensive (Y-NT, AGE=30±2 yrs), older normotensive (O-NT, AGE=59±2 yrs), young hypertensive (Y-HT, AGE =36±1 yrs), and older hypertensive (O-HT, AGE=58±1 yrs) are presented: The age-related attenuation in cardiac response to phenylephrine is already present in young hypertensives. The absence of baroreflex-mediated decrease in cardiac function enhances the BP response to vasopressive stimuli.