Blood Pressure

1
Blood Pressure Cardiovascular Center

• Laura, Jessica, Michelle and Tigest

2
Problem

• A 47- year old teacher goes to her physician
  complaining of dizziness, fainting, and shortness
  of breath. Objective evaluation reveals HR 70
  supine, 68 sitting, and 68 standing BP 120/74
  supine, 98/54 sitting, 84/48 standing. Heart and
  lungs sounds are normal. General neurologic exam
  is normal. Routine labs are normal.

3
Questions

• What is abnormal about her examination?
• How does this information help explain her
  symptoms.
• List all the functional locations within
  cardiovascular regulation where pathology could
  lead to these changes. Further tests were
  performed in an attempt to identify the
  pathology
• 1) Administration of atropine did not result in
  any changes in heart rate.
• 2) Administration of isoproterenol resulted in
  increase in heart rate from 60 to 118 bpm.
• Are these responses normal? Where do you think
  the pathology lies?

4
The Reflex Arc
Which of these components is the source of the
problem?
5
Abnormal

• Heart and blood vessels are not responding
  diastolic pressure is going down and systolic is
  not going up.
• HR 70 supine, 68 sitting, and 68 standing
  BP 120/74 supine, 98/54 sitting, 84/48
  standing
• You need an increase MAP so that blood can go to
  the brain.
• SNS to the heart and blood vessels should
  increase cardiac output (raising systolic
  pressure), and increase vasoconstriction
  (increasing venous return and raising diastolic
  pressure)
• Her heart cant efficiently pump blood against
  the gravity, causing dizziness and fainting.

6
Atropine

• An anti-parasympathetic drug
• Parasympathetic antagonist
• Should leave sympathetic input without the
  balancing effect of the parasympathetic input
• This should raise the heart rate
• The teacher had no reaction to Atropine

7
Isoproterenol

• It is a specific Beta1 agonist (receptors only
  found in the heart and kidneys)
• When it is administered, isoproterenol stimulates
  these sympathetic receptors (as NE would) and
  increases heart rate
• When isoproterenol was given to our teacher, her
  heart rate increased from 60 to 118 bpm which
  leads us to believe that the receptors for NE at
  her heart are not the cause of her poor blood
  pressure regulation

8
Autonomic Cardiovascular Regulation
http//www.usc.edu/hsc/pharmacy/ced/autonomic/Hear
tBlowUp.html
9
Where does the pathology lie?

• By administering atropine and isoproterenol, it
  helped identify that the pathology is in the
  nervous system, but where?
• Baroreceptors
• Afferent nerves
• Cardiovascular Center in the medulla
• Efferent nerves

?
10
Analogy

• Atropine and Isoproterenol should both deliver a
  message that says increase HR
• While you are out, someone calls and leaves a
  message with your roommate (who doesnt write it
  down!), and then calls back later and leaves the
  same message on your answering machine (increase
  HR).
• The answering machine is the functional beta 1
  receptors, and Isoproterenol (in place of NE) is
  the message on the answering machine.
• By listening to the answering machine you get the
  message right away. (i.e. the receptors listen
  to the message and respond appropriately.)

11
Analogy

• Your roommate is the dysfunctional message
  control center (CV center) that fails to deliver
  the message.
• Even though a signal was received, it was
  ineffective because the pathway was disrupted-
  you didnt receive the message.