coronary circulation

Question 1

oxygen supply

Answer 1

heart has limited anaerobic capacities, a lack of O2 can decline contractility in seconds.
the heart has the highest oxygen consumption per gram of all organs of the body
O2 extraction is 40-80% compared to 30-40% for skeletal muscle

Question 2

how much volume is coronary blood flow

Answer 2

at rest coronary blood flow is 225ml/min

4-5% of CO

Question 3

cardiac perfusion

Answer 3

coronaries are perfused during diastole and are fed with systolic pressure. this is due to anatomical location of the ostia

Question 4

What is the primary factor which affects coronary blood flow ?

Answer 4

metabolic demand
when myocardial Oxygen consumption (MVO2) increases vasodilation should occur
when MV2 decreases there will be vasocontraction

Question 5

coronary perfusion pressure

Answer 5

normal range is 60-80mmhg
<80mmHg- decrease in coronary blood flow due to reflex vasoconstriction
<60mmhg=usually poor perfusion especially with increase HR or acute MI
<40 mmHg= collapse of coronary vessels

Question 6

autoregulation

Answer 6

the intrinsic tendency of an organ to maintain blood flow despite changes in arterial perfusion pressure

Question 7

myocardial perfusion factors

Answer 7

1. ) extravascular compressive forces
2. )Diastolic time fraction
3. )Coronary perfusion pressure
4. )Myocardial Metabolism
5. )Endothelial derived substances
6. )Neuro-hormonal influences
7. )Arterial oxygen tension and content

Question 8

what are the factors affecting vasodilation

Answer 8

• PaO2- hypoxia
• nitric oxide
• adenosine
• K
• lactate
• prostaglandins

Question 9

Angina

Answer 9

chest pain

Question 10

considerations for disease

Answer 10

perfusion is tightly regulated to match demand introduction of a disease that reduces blood flow will trigger the autoregulatory system to compensate for the loss flow (vasodilation) . As disease progresses this autoregulatory system is not able to keep up.