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High Resolution Phenotyping in Healthy Humans

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details.
 
ClinicalTrials.gov Identifier: NCT00943774
Recruitment Status : Completed
First Posted : July 22, 2009
Last Update Posted : January 6, 2016
Sponsor:
Collaborator:
National Heart, Lung, and Blood Institute (NHLBI)
Information provided by (Responsible Party):
John Eisenach, Mayo Clinic

Tracking Information
First Submitted Date July 20, 2009
First Posted Date July 22, 2009
Last Update Posted Date January 6, 2016
Study Start Date April 2006
Actual Primary Completion Date February 2013   (Final data collection date for primary outcome measure)
Current Primary Outcome Measures
 (submitted: July 20, 2009)
Blood Pressure Response to Sympathoexcitation [ Time Frame: On day of study ]
Original Primary Outcome Measures Same as current
Change History
Current Secondary Outcome Measures
 (submitted: July 20, 2009)
Baroreflex Sensitivity [ Time Frame: On day of study ]
Original Secondary Outcome Measures Same as current
Current Other Pre-specified Outcome Measures Not Provided
Original Other Pre-specified Outcome Measures Not Provided
 
Descriptive Information
Brief Title High Resolution Phenotyping in Healthy Humans
Official Title Blood Pressure Variability, Baroreflex Sensitivity, and Cardiovascular Responses to Sympathoexcitation in Healthy Normotensive Humans
Brief Summary Baroreflex sensitivity is integral to blood pressure regulation, and varies among healthy, normotensive individuals. A reduced compensatory ability of baroreflex buffering in patients with carotid denervation results in blood pressure variability and an elevated blood pressure response to mental stress. Furthermore, 24-hour ambulatory blood pressure variability may also be a significant and independent risk determinant of cardiovascular disease. It remains unknown whether the degree of baroreflex sensitivity and ambulatory blood pressure variability are predictive of the pressor response to sympathoexcitatory stress in healthy humans. In this study the investigators propose a comprehensive evaluation of the relationships among the pressor and forearm vasodilator response to sympathoexcitation, ambulatory blood pressure variability, and baroreflex sensitivity in healthy normotensive subjects. Ultimately this study will provide preliminary data and protocol development for large-scale high resolution phenotyping in population-based trials aimed at determining the functional relevance of candidate gene variation in intermediate physiological traits pertinent to the pathogenesis of hypertension and cardiovascular disease.
Detailed Description

Growing evidence suggests an association of environmental stress with the development of hypertension and there is strong evidence in normotensive subjects that a greater pressor response to sympathoexcitatory stress is a harbinger of future hypertension. Pharmacological studies have shown that individuals with HTN have a blunted baroreflex sensitivity, and display a greater increase in blood pressure during administration of an alpha-agonist. Furthermore, exaggerated 24-hour ambulatory blood pressure variability (BPV) is proposed to be a risk factor for the development of cardiovascular disease. Finally, Beta-2 adrenergic receptor-mediated forearm vasodilator responses to mental stress are blunted in Caucasian subjects at increased risk for hypertension, in African Americans, and in mild hypertension. We postulate that a relationship exists between these variables, even in normotensive healthy individuals. We also believe that signs of subclinical metabolic dysfunction exist in healthy individuals and that they may either contribute to or be affected by BPV. There is also evidence the prematurity at birth and low birth weight are associated with hypertension. Finally, arterial stiffness may also be related to blood pressure variability and the pressor response. Therefore the specific aims of this study are:

  1. To examine the relationship between 24-hour ambulatory BPV and baroreflex sensitivity. By measuring the baroreflex control of heart rate during sequential boluses of nitroprusside and phenylephrine, we hypothesize that baroreflex sensitivity will be inversely related to the degree of 24-hour BPV.
  2. To examine the relationship between 24-hour ambulatory BPV and the pressor response to four sympathoexcitatory maneuvers: head-up tilt testing, mental stress, cold pressor test, and isometric handgrip to fatigue. We hypothesize that greater BPV will predict the pressor response to stress.
  3. To examine the relationship between baroreflex sensitivity and the pressor response/forearm vasodilator response to the three sympathoexcitatory maneuvers. We hypothesize that individuals with higher baroreflex sensitivity will have a lower pressor response and a lower forearm vasodilator response to sympathoexcitatory stress.
  4. To draw a venous blood sample for future screening of genetic polymorphisms of interest, which may include nitric oxide synthase (NOS), alpha-adrenergic and beta-adrenergic receptor polymorphisms. We hypothesize that genetic variation in these key regulatory systems might explain some of the differences in baroreflex sensitivity, BPV, the pressor response and forearm vasodilator response to sympathoexcitation.
  5. To examine the relationship between 24-hour ambulatory BPV and the pressor response to sympathoexcitatory maneuvers and insulin resistance, dyslipidemia, and body fat distribution. We hypothesize that greater BPV will be associated with insulin resistance, dyslipidemia, and increase waist-hip ratio.
  6. To examine the relationship between 24-hour ambulatory BPV and arterial stiffness using measurements of pulse wave velocity. We hypothesize that greater BPV will be associated with increased pulse wave velocity, an index of arterial stiffness.
  7. To examine the relationship between 24-hour ambulatory BPV and the pressor response to sympathoexcitatory maneuvers with birth weight and post-conceptual age at birth. We will ask each subject to provide this data based on their birth certificate and/or knowledge of their medical history.
Study Type Observational
Study Design Observational Model: Cohort
Time Perspective: Prospective
Target Follow-Up Duration Not Provided
Biospecimen Retention:   Samples With DNA
Description:
serum, white cells
Sampling Method Non-Probability Sample
Study Population Residents of Southeast Minnesota
Condition
  • Pressor Response
  • Baroreflex Sensitivity
  • Blood Pressure Variability
  • Heart Rate Variability
  • Arterial Catecholamines
Intervention Other: Physiological maneuvers
These healthy subjects undergo physiological testing, which includes aortic augmentation index, pulse wave velocity, orthostatic stress, baroreflex sensitivity (modified Oxford protocol), mental stress, cold pressor test, isometric handgrip, heart rate variability, 24-hour ambulatory blood pressure monitoring.
Study Groups/Cohorts All subjects
All subject participants
Intervention: Other: Physiological maneuvers
Publications *

*   Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
 
Recruitment Information
Recruitment Status Completed
Actual Enrollment
 (submitted: July 20, 2009)
300
Original Estimated Enrollment Same as current
Actual Study Completion Date February 2013
Actual Primary Completion Date February 2013   (Final data collection date for primary outcome measure)
Eligibility Criteria

Inclusion Criteria:

  • Men age 18-40
  • Non-pregnant women age 18-50

Exclusion Criteria:

  • Any medical conditions affecting the cardiovascular system
  • Any prescribed chronic medications (except contraceptives)
  • Extremes of fitness (not totally sedentary, not highly exercise-trained)
  • BMI greater than 28
Sex/Gender
Sexes Eligible for Study: All
Ages 18 Years to 50 Years   (Adult)
Accepts Healthy Volunteers Yes
Contacts Contact information is only displayed when the study is recruiting subjects
Listed Location Countries United States
Removed Location Countries  
 
Administrative Information
NCT Number NCT00943774
Other Study ID Numbers 05-004352
R01HL089331 ( U.S. NIH Grant/Contract )
NS-32352
Has Data Monitoring Committee Yes
U.S. FDA-regulated Product Not Provided
IPD Sharing Statement Not Provided
Responsible Party John Eisenach, Mayo Clinic
Study Sponsor Mayo Clinic
Collaborators National Heart, Lung, and Blood Institute (NHLBI)
Investigators Not Provided
PRS Account Mayo Clinic
Verification Date January 2016