Nocturnal Blood Pressure Dipping in the Hypertension of Autonomic Failure

Abstract

Blood pressure (BP) normally decreases during the night. Absence of this phenomenon (nondipping) is associated with increased cardiovascular risk. Altered autonomic and endocrine circadian rhythms are suspected to play a role. Patients with peripheral autonomic failure offer a unique opportunity to study this phenomenon, because ≈50% develop supine hypertension despite very low autonomic function. The purpose of this study was to define the prevalence of dipping in these patients and to determine whether dipping is associated with less severe autonomic impairment or exaggerated nocturnal sodium excretion. We collected BP and urine from 8:00 pm to 8:00 am in 41 peripheral autonomic failure patients with supine hypertension. Dipping (systolic BP fall ≥10% during 12 am to 6 am from baseline [8 pm to 10 pm]) occurred in 34% of patients, with an average decrease of −44±4 mm Hg at 4 am. Systolic BP, averaged from 12 am to 6 am, decreased to normotensive levels in 50% (n=7) of dippers and 15% (n=7) of nondippers...