3- Coronary Circulation

Question 1

coronary arteries

Answer 1

from aorta to supply heart
1. R coronary = R heart + part posterior LV
2. L circumflex = lateral free wall + LA
3. L anterior descending = anterior + lateral LV + part septum

Question 2

flow from epicardium to endocardium

Answer 2

large coronary vessels on epicardial surface
-send branches into myocardium
-continue into inner surface of ventricle/endocardium

Question 3

pressure on coronary vessels

Answer 3

highest on subendothelial vessels bc compresion from force of blood in chamber

since downstream of muscles when contraction then compromise flow

Question 4

inlet/outlet pressure

Answer 4

inlet = aortic P that pushes blood into coronary circ
outlet= R atrial P (usually 0)

so since aortic P varies then flow varies, not stable

Question 5

when best perfused?

Answer 5

LV maximally perfused during diastole bc not contracting and minimally during systole
-lowest flow during isovolumic contraction

if change diastole then change perfusion
-inc HR = dec diastole = compromise more

Question 6

wall tension = ? flow

Answer 6

reduces coronary blood flow

Question 7

autoregulation

Answer 7

maintenance of constant blood flow over range of perfusion rates

Question 8

regulators of coronory circ

Answer 8

1. perfusion pressure
2. extravascular compression
3. metabolsim
4. myogenic response
5. autonomic mechanisms

to optimize oxygen supply and get blood into coronary cap network

Question 9

myogenic response

Answer 9

stretch operated ion channels resp to changes in pressure to effect changes in resistance

Question 10

metabolites on coronary flow

Answer 10

inc metabolism requires inc coronary flow

adenosine major metabolite for vasodilation (from hypoxia stimulus)

Question 11

metabolic pathway -coronary circ

Answer 11

1. inc metabolism
2. mismatch oxy supply/demand = inc hypoxia
3. inc ATP turnover
4. inc cellular adenosine accumulation that diffuses out of cardiac cell
5. vasodilation

Question 12

only way to inc oxygen delivery

Answer 12

inc blood flow/ vasodilation

bc heart muscle extracts lot of oxygen so when heart need more oxy like exercise

Question 13

coronary reserve

Answer 13

diff b/t passive movement from pressure and autoreg curve
-reflects ability to vasodilate so if impaired vasodilation then reduced reserve

Question 14

sympathetic regulation

Answer 14

1. transient vasoconstrict from NE on alpha adrenergic receptors, direct
2. inc force contraction + HR = vasodilate and inc blood flow, indirect, most pronounced effect