Vascular α1-Adrenergic Receptor Responsiveness in Masked Hypertension

BACKGROUND: Masked hypertension (nonhypertensive in the clinic setting but hypertensive outside the clinic during wakefulness) is characterized by increased blood pressure in response to physical and emotional stressors that activate the sympathetic nervous system (SNS). However, no studies have assessed vascular reactivity to a pharmacological SNS challenge in individuals with masked hypertension. METHODS: We analyzed data from 161 adults aged 25 to 45 years (mean ± standard deviation age 33 ± 6 years; 48% were African American and 43% were female). Participants completed ambulatory blood pressure monitoring, and a standardized α 1-adrenergic agonist phenylephrine test that determines the dose of phenylephrine required to increase a participant's mean arterial pressure by 25 mm Hg (PD25). RESULTS: Twenty-one participants were considered to have masked hypertension (clinic systolic blood pressure (SBP) <140 and diastolic blood pressure (DBP) <90 mm Hg but awake SBP ≥135 or DBP ≥85 mm Hg), 28 had sustained hypertension (clinic SBP ≥140 or DBP ≥90 mm Hg and awake SBP ≥135 or DBP ≥85 mm Hg), and 106 had sustained normotension (clinic SBP <140 and DBP <90 mm Hg and awake SBP <135 and DBP <85 mm Hg). After multivariable adjustment, the mean (±SE) PD25 was less in participants with masked hypertension compared with their counterparts with sustained normotension (222.1 ± 33.2 vs. 328.7 ± 15.0; P = 0.012), but similar to that observed in subjects with sustained hypertension (254.8 ± 31.0; P =0.12). CONCLUSIONS: Among young and middle-aged adults, masked hypertension is associated with increased vascular reactivity to a SNS challenge, which may contribute to elevated awake BPs as well as to increased cardiovascular disease risk.