The Role of Endothelin in the Supine Hypertension of Autonomic Failure
The purpose of this study is to test the hypothesis that endothelin plays a role in the pathogenesis of supine hypertension in pure autonomic failure by increasing vascular resistance. To gauge its contribution to blood pressure regulation, pure autonomic failure and multiple system atrophy patients with supine hypertension will undergo a medication testing with the endothelin blocker, BQ123. We will compare the hemodynamic effects between PAF and MSA patients. Our primary endpoint will be the decrease in blood pressure during the administration of this compound.
Pure Autonomic Failure
Multiple System Atrophy
|Study Design:||Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single Blind (Subject)
|Official Title:||The Role of Endothelin in the Supine Hypertension of Autonomic Failure|
- Change in Systolic BP [ Time Frame: 0 -4 hr post infusion ] [ Designated as safety issue: No ]
- Change in cardiac output, stroke volume and systemic vascular resistance [ Time Frame: 0-4 hr post infusion ] [ Designated as safety issue: No ]
|Study Start Date:||May 2010|
|Estimated Study Completion Date:||November 2014|
|Estimated Primary Completion Date:||November 2014 (Final data collection date for primary outcome measure)|
Low dose day: 25 nmol/min, single IV infusion for 15 min.
Other Name: BQ-123 sodium saltDrug: BQ123
Low dose day: 50 nmol/min, single IV infusion for 15 min
Other Name: BQ-123 sodium saltDrug: Bq123
High dose day: 100 nmol/min, single IV infusion for 15 min.
Other Name: BQ-123 sodium saltDrug: BQ123
High dose day: 300 nmol/min, single IV infusion for 15 min.
Other Name: BQ-123 sodium salt
Placebo Comparator: Saline
2-3 IV saline infusions for 15 min each.
Other Name: Normal saline, 0.9% sodium chloride
The pathophysiologic mechanisms causing supine hypertension in patients with autonomic failure are not completely understood.In MSA patients, supine hypertension may be explained by residual sympathetic tone, possibly acting on hypersensitive adrenoreceptors and unstrained by the lack of baroreflex modulation. In contrast, the pathogenesis of hypertension in PAF remains unknown. Hypertension in these patients is not related to intravascular volume, residual sympathetic tone, or renin mechanisms. Increased vascular resistance is the underlying hemodynamic mechanism. The driving force of this increased vascular tone, however, is not known.
We hypothesize that endothelin (ET)-l contributes to the increased vascular resistance in pure autonomic failure patients with supine hypertension. To gauge its contribution to blood pressure regulation, we will induce endothelin blockade with acute systemic administration of BQ123 in an ascending dose regimen (25, 50, 100 and 300 nmol/min) and we will compare the hemodynamic effects between PAF and MSA patients.
Subjects will be studied on 3 different days, one with saline (placebo) and two with BQ123: a 'low dose' day (25 and 50 nmol/min infusions separated by 75 min) and a 'high dose' day (100 and 300 nmol/min infusions separated by 75 min). The order of the placebo day will be randomized in a single-blinded manner so that each subject receives it on a different visit. The order of the BQ123 study days will be always the same, starting with the low dose. If SBP drops by >40 mm Hg or SBP < 130 mm Hg during the monitoring period after the first or second infusion, the following dose(s) of BQ123 will not be given and patients will receive normal saline until the study ends.
Ganglionic Blockade with Trimethaphan (optional study day):
The purpose of this study day is to determine the level of residual sympathetic tone that contributes to supine hypertension in each autonomic failure patient by inducing transient withdrawal of the autonomic nervous system. This approach would allow us to identify patients in whom supine hypertension is not driven by sympathetic tone and thus, better characterize the role of endothelin in the hypertension of these patients.
|Contact: Bonnie K Black, R.N.||email@example.com|
|United States, Tennessee|
|Nashville, Tennessee, United States, 37232|
|Contact: Bonnie Black, RN firstname.lastname@example.org|
|Principal Investigator: Biaggioni Italo, MD|
|Sub-Investigator: Cyndya Shibao, MD|
|Sub-Investigator: David Robertson, MD|
|Sub-Investigator: Andre Diedrich, MD|
|Sub-Investigator: Alfredo Gamboa, MD|
|Sub-Investigator: Satish Raj, MD|
|Sub-Investigator: Luis E Okamoto, MD|
|Sub-Investigator: Hossam Mustafa, MD|
|Sub-Investigator: Amy C Arnold, PhD|
|Principal Investigator:||Italo Biaggioni, M.D.||Vanderbilt University|