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33 Cards in this Set

  • Front
  • Back
Why discuss coronary circulation?
Lots of deaths are linked to CAD - more deaths are of cardiovascular causes than cancer.
3 irreversible risk factors of CAD:
-Male sex
-Genetic predisposition
4 Reversible risk factors related to CAD:
-Increased blood pressure
-Cardiac hypertrophy
3 Partially reversible risk factors for CAD:
-Increased cholesterol/triglyc
-Hyperglycemia/diabetes mellitus
-Low levels of HDL
3 Other risk factors for CAD:
-Personality type
-Physical inactivity
-C-reactive protein
Normal resting coronary bloodflow:
225 ml/min
What percentage of CO is resting CBF?
But how high is flow/unit weight of CBF?
pretty high
How does CBF change during exercise?
Not as much as the heart's work output or CO increase.
What is the increase during strenuous exercise of:
-Work output of heart
Co: 4-7X increase
Work output of heart: 6-9X incr
CBF: 3-4X increase
2 reasons for why CBF does not increase all that much during exercise:
1. Can extract more oxygen from hemoglobin
2. The heart's energy use becomes more efficient to make up for the relative deficiency of blood supply.
What is the "utilization coefficient"?
The ratio of the difference in O2 between Arteries and Veins to the total O2 in arteries
What does the utilization coefficient tell us?
What oxygen is NOT in the arteries or veins; hence the oxygen that is in the coronary arteries.
Why is it funny to say things like "Resting CBF"?
Because the heart is never really resting; it's always pumping.
What is the utilization coefficient in coronary circulation?
75% - the amt that is taken out and used by coronary circulation.
Is there much room for increasing oxygen extraction in the coronary circulation?
Why can't coronary bloodflow extract much more O2 during exercise?
Becasue under normal conditions it already extracts quite a bit - 75%.
What is the Art O2 content?
What is the Ven O2 content?
Art = 20 ml/100 ml blood
Ven = 5 ml/100 ml blood
How does coronary bloodflow increase during exercise if it can't increase oxygen extraction? (2 ways)
1. By increasing flow
2. By increasing its efficiency of energy utilization.
What happens to coronary bloodflow during systole?
Coronary perfusion is decreased during systole.
How does coronary perfusion relate to skeletal/systemic perfusion during the cardiac cycle?
Oppositely! When the heart is contracting, systemic perfusion is high but coronary perfusion is low.
Why is coronary perfusion low during systole?
1. Because the muscle is contracting and this reduces ability of blood to flow
2. Because the coronary vessel outputs are located behind the aortic valve.
Why is the fact that coronary perfusion is low during systole an important fact?
Because when the HR is high the cardiac cycle is faster and there is less time for coronary tissue reperfusion during short diastole - but systole stays the same length.
How are Diastole and Systole changed during high heartrate?
Diastole is shorter
Systole is a little shorter but not as much as diastole.
3 types of coronary vessels:
1. Epicardial
2. Intramuscular
3. Subendocardial
What coronary vessels are affected most by decreased perfusion during systole?
Subendocardial / intramuscular
How does CBF during systole compare between Epicardial vessels and Subendocardial vessels?
Sub - almost shut down completely during systole
Epi - not nearly as affected by systole
What are the 2 main controllers of CBF?
1. Myocardial O2 consumption driven by work output
2. Adenosine (released when O2 is decreased)
So the dominant factor that controls cardiac bloodflow is:
OXYGEN - which makes sense since the whole purpose of the heart is to circulate oxygen...
How much of an impact does nervous stimulation have on controlling CBF?
NOT much - mainly on epiardial flow via alpha adrenergic receptors.
Where does the heart get 70% of its energy for metabolism?
Fatty acids
3 Sites of venous drainage of the heart:
-Coronary sinus (drains the left ventricle into right atrium)
-Anterior cardiac veins (drain the right ventricle)
-Thebesian veins (cavities)
What feature of coronary circulation helps prevent heart failure in cases of blockage?
Minute anastomoses in the normal coronary areterial system.