CV 8

Question 1

How much oxygen does the heart usually extract

Answer 1

70-80% extraction

Cannot increase oxygen supply by increasing extraction

Question 2

Right coronary artery

Answer 2

Travels in right AV groove
Acute marginal branches that feed RA and RV
Posterior descending artery feeds posterior wall

Question 3

Left coronary artery

Answer 3

Feeds most of septum, LV and LA

Splits into left anterior descending artery and left circumflex artery in AV groove

Question 4

Left anterior descending artery

Answer 4

Branch of LCA

Extends down anterior ventricular septum towards apex

Question 5

Coronary perfusion pressure

Answer 5

BP within coronary pressure

Question 6

When is there maximal flow and perfusion to the LV?

Answer 6

During diastole

Question 7

What happens to the vasculature during systole?

Answer 7

Heart contracts
Muscle tension compresses the coronary vasculature and obstructs blood flow
Least flow near endocardium

Question 8

What happens to the vasculature during diastole?

Answer 8

Heart relaxed

No compression so blood can flow freely

Question 9

Coronary perfusion pressure approximated by…

Answer 9

Aortic diastolic pressure

Question 10

3 things that effect myocardial metabolic rate

Answer 10

Heart rate
Contractility
Wall stress

Question 11

What changes to the ST segment do you see during subendocardial ischemia?

Answer 11

ST depression
(horizontal depression, downsloping, or T wave inversion)

Question 12

What changes to the ST segment do you see during transmural ischemia?

Answer 12

ST elevation

Question 13

Adenosine

Answer 13

Potent vasodilator of VSM
Binds to receptor, decreases Ca entry
Most important metabolic regulator of coronary flow
No oxygen, not enough ATP = more ADP, breaks down into adenosine, can leave muscles and bind causes dilation

Question 14

3 vasodilators

Answer 14

NO
Prostacyclin (PGI2)
Endothelium-derived hyperpolarizing factor (EDHF)

Question 15

1 examples of a vasoconstrictor

Answer 15

Endothelin 1

Question 16

Fixed vessel narrowing

Answer 16

Atherosclerotic plaque narrow vessels and therefore increase resistance to flow
Compensation occurs by downstream dilation due to local metabolic need
Occurs in large arteries where there is a higher chance of turbulence

Question 17

Endothelial cell dysfunction

Answer 17

Occurs early in atherosclerosis
Impaired release of vasodilators
Attenuated effect of local metabolites
Relative vasoconstriction occurs

Question 18

What happens to
1. Normal resting flow
2. Maximal flow
at 70% occlusion?

Answer 18

1. Normal

2. Low

Question 19

What happens to
1. Normal resting flow
2. Maximal flow
at 90% occlusion?

Answer 19

1. Low

2. Low

Question 20

Myocardial O2 supply depends on (2)

Answer 20

Arterial O2 content

Coronary blood flow

Question 21

Myocardial demand depends on (1)

Answer 21

Myocardial metabolic rate