Association between supine hypertension and orthostatic hypotension in chronic autonomic failure

Supine hypertension occurs commonly in primary chronic autonomic failure. This study explored whether supine hypertension in this setting is associated with orthostatic hypotension (OH) and, if so, what mechanisms underlie this association. Supine and upright blood pressure, hemodynamic responses to the Valsalva maneuver, and plasma norepinephrine levels were measured in pure autonomic failure (PAF), multiple system atrophy (MSA) with or without OH, and Parkinson's disease (PD) with or without OH. Controls included age-matched normal volunteers and patients with essential hypertension (EH) or referred for dysautonomia. PAF, MSA+OH, and PD+OH all featured supine hypertension equivalent in severity to that in EH, regardless of fludrocortisone treatment for OH. Patients with MSA or PD lacking OH did not have supine hypertension. Individual values for supine mean arterial pressure correlated negatively with orthostatic changes in mean arterial pressure (r=-0.40, p<0.0001). Baroreflex-cardiovagal gain and orthostatic increments in plasma norepinephrine levels were markedly decreased in all groups with OH. In both MSA and PD, norepinephrine levels during supine rest were lower in the subgroups with than without supine hypertension. In chronic primary autonomic failure, supine hypertension accompanies OH. Decreased baroreflex-cadiovagal gain correlates with and therefore might play a pathophysiologic role in both abnormalities of blood pressure regulation. Increased delivery of norepinephrine to its receptors does not adequately explain supine hypertension in patients with primary chronic autonomic failure and OH, suggesting a hypertensive mechanism independent of the sympathetic nervous system.