Medical Student Research Fellowship for Summer 2007
Mentor: Qi Fu, M.D., Ph.D.
Department: Internal Medicine, Cardiology Division
Room number: Institute for Exercise and Environmental Medicine,
7232 Greenville Ave., suite 435, Dallas, TX
Mail Code:
Phone number: 214-345-8125
E-mail: QiFu@TexasHealth.org
Project title: Gender & Orthostatic Intolerance: Mechanisms and Therapy
Human subjects IRB approved project number (where applicable): #01204-017
Animal subjects IRB approved project number (where applicable): NA
Project Type (patient-based research, animal-based research, or basic research;
this characterization is only to permit a general classification for grouping
similar types of projects):
Patient-based research.
Brief Description of Project:
The primary objective of this project is to determine the mechanisms underlying
gender differences in orthostatic tolerance including neurohumoral influences
on cardiovascular control processes and physical characteristics (primarily
cardiac size and function) that determine orthostatic distribution of central
blood volume. Menstrual cycle variability in young women, and differences among
men, women, and women with Postural Orthostatic Tachycardia Syndrome (POTS,
also called Chronic Orthostatic Intolerance, in which patients are unable to
stand or remain upright for prolonged periods of time due to intolerable light
headedness, weakness, and near-syncope) will be examined. Finally, "optimized"
exercise training will be studied as a specific therapy for patients with POTS
and compared with "standard" pharmacologic therapies.
Previous Research Activities or Publications with Medical Students:
1. 03/2006 - Present
I am the Principal Investigator (PI) of a research entitled "Vasomotor
Sympathetic Activity during Early Pregnancy in Humans". In this project
we are investigating vasomotor sympathetic neural control of hemodyanmics in
normal human pregnancy, especially during the early stage of pregnancy.
2. 04/2004 - Present
I am the PI of a research project funded by the National Institutes of Health
National Heart, Lung, and Blood Institute (NIH) entitled "Gender &
Orthostatic Intolerance: Mechanisms and Therapy." In this project we are
studying the mechanisms underlying gender differences in orthostatic tolerance
including neurohumoral influences on cardiovascular control processes and physical
characteristics (primarily cardiac size and function) that determine orthostatic
distribution of central blood volume. Menstrual cycle variability in young women,
and differences among men, women, and women with Postural Orthostatic Tachycardia
Syndrome (POTS, also called Chronic Orthostatic Intolerance, in which patients
are unable to stand or remain upright for prolonged periods of time due to intolerable
light headedness, weakness, and near-syncope) will be examined. Finally, "optimized"
exercise training will be studied as a specific therapy for patients with POTS
and compared with standard pharmacologic therapies.
3. 09/2001 - 04/2004
1) I was the Principal Investigator (PI) of a research project funded by the
American Heart Association (AHA) entitled "Vasoconstrictor Reserve: A Mechanism
for Individual Variability of Orthostatic Intolerance?" In this project
we studied whether each human individual had a finite range of maximal vascular
resistance that could be mediated by adrenergic activity; whether a limited
vasoconstrictor reserve could result in reduced orthostatic tolerance; and whether
orthostatic intolerance during hypovolemia was a direct function of the capacity
for vasoconstrictor reserve. We used microneurographic technique to measure
vasomotor sympathetic outflow to the muscles (which is called muscle sympathetic
nerve activity, performed by myself), Doppler ultrasound to measure femoral
blood flow, re-breathing method to measure cardiac output, Finapres and Suntech
to measure blood pressure, and electrocardiogram to measure heart rate. We applied
head-up tilt and/or lower body negative pressure to simulate the orthostatic
stress, and used the cold pressor test during upright tilting to measure the
vasoconstrictor reserve. We determined the relationships between the sympathetic
neural responses, the peak increases in vascular resistance (general and regional),
and the maximal orthostatic tolerance in each healthy individual subject. This
research was particularly important for understanding the mechanism of individual
difference in orthostatic tolerance in human beings.
2) I was involved in a study entitled "Dynamic Cerebral Autoregulation
during Acute and Chronic Treatment of Hypertension." In this project (funded
by the American Heart Association (AHA), we studied how treatment of both mild
and moderate hypertension improves dynamic autoregulation in the brain, using
novel techniques described by our research group (Zhang R, Zuckerman JH, Giller
CA, and Levine BD. Tansfer function analysis of dynamic cerebral autoregulation
in humans. Am J Physiol Heart Circ Physiol 274: H233-H241, 1998). We measured
regional (forearm and brain) and systemic hemodynamics both supine and during
70 degrees upright tilt, and evaluated baroreflex function using the Valsalva
maneuver in well characterized subjects at baseline, after 1-2 weeks of therapy
with a combined diuretic/angiotensin receptor antagonist (Hyzar), and again
after 3 months of chronic therapy. We were particularly interested in how the
autonomic nervous system was involved in the regulation of cerebral blood flow,
and how acute and chronic anti-hypertensive therapy altered baroreflex control
of muscle sympathetic nerve activity in patients with moderate hypertension.
To our knowledge, this was one of the first studies to investigate sympathetic
nerve activity progressively over the time in patients during treatment of hypertension.
Return to Medical Student Research Page