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33 Cards in this Set
- Front
- Back
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Why discuss coronary circulation?
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Lots of deaths are linked to CAD - more deaths are of cardiovascular causes than cancer.
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3 irreversible risk factors of CAD:
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-Aging
-Male sex -Genetic predisposition |
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4 Reversible risk factors related to CAD:
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-Smoking
-Increased blood pressure -Obesity -Cardiac hypertrophy |
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3 Partially reversible risk factors for CAD:
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-Increased cholesterol/triglyc
-Hyperglycemia/diabetes mellitus -Low levels of HDL |
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3 Other risk factors for CAD:
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-Personality type
-Physical inactivity -C-reactive protein |
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Normal resting coronary bloodflow:
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225 ml/min
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What percentage of CO is resting CBF?
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4-5%
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But how high is flow/unit weight of CBF?
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pretty high
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How does CBF change during exercise?
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Not as much as the heart's work output or CO increase.
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What is the increase during strenuous exercise of:
-CO -Work output of heart -CBF |
Co: 4-7X increase
Work output of heart: 6-9X incr CBF: 3-4X increase |
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2 reasons for why CBF does not increase all that much during exercise:
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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. |
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What is the "utilization coefficient"?
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The ratio of the difference in O2 between Arteries and Veins to the total O2 in arteries
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What does the utilization coefficient tell us?
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What oxygen is NOT in the arteries or veins; hence the oxygen that is in the coronary arteries.
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Why is it funny to say things like "Resting CBF"?
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Because the heart is never really resting; it's always pumping.
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What is the utilization coefficient in coronary circulation?
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75% - the amt that is taken out and used by coronary circulation.
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Is there much room for increasing oxygen extraction in the coronary circulation?
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No;
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Why can't coronary bloodflow extract much more O2 during exercise?
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Becasue under normal conditions it already extracts quite a bit - 75%.
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What is the Art O2 content?
What is the Ven O2 content? |
Art = 20 ml/100 ml blood
Ven = 5 ml/100 ml blood |
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How does coronary bloodflow increase during exercise if it can't increase oxygen extraction? (2 ways)
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1. By increasing flow
2. By increasing its efficiency of energy utilization. |
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What happens to coronary bloodflow during systole?
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Coronary perfusion is decreased during systole.
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How does coronary perfusion relate to skeletal/systemic perfusion during the cardiac cycle?
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Oppositely! When the heart is contracting, systemic perfusion is high but coronary perfusion is low.
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Why is coronary perfusion low during systole?
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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. |
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Why is the fact that coronary perfusion is low during systole an important fact?
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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.
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How are Diastole and Systole changed during high heartrate?
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Diastole is shorter
Systole is a little shorter but not as much as diastole. |
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3 types of coronary vessels:
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1. Epicardial
2. Intramuscular 3. Subendocardial |
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What coronary vessels are affected most by decreased perfusion during systole?
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Subendocardial / intramuscular
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How does CBF during systole compare between Epicardial vessels and Subendocardial vessels?
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Sub - almost shut down completely during systole
Epi - not nearly as affected by systole |
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What are the 2 main controllers of CBF?
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1. Myocardial O2 consumption driven by work output
2. Adenosine (released when O2 is decreased) |
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So the dominant factor that controls cardiac bloodflow is:
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OXYGEN - which makes sense since the whole purpose of the heart is to circulate oxygen...
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How much of an impact does nervous stimulation have on controlling CBF?
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NOT much - mainly on epiardial flow via alpha adrenergic receptors.
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Where does the heart get 70% of its energy for metabolism?
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Fatty acids
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3 Sites of venous drainage of the heart:
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-Coronary sinus (drains the left ventricle into right atrium)
-Anterior cardiac veins (drain the right ventricle) -Thebesian veins (cavities) |
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What feature of coronary circulation helps prevent heart failure in cases of blockage?
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Minute anastomoses in the normal coronary areterial system.
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