Regulation of Coronary Circulation

Question 1

The clinical manifestation of the alterations in the delivery of blood supply to the myocardium.

Answer 1

Coronary heart disease

Question 2

3 determinants of myocardial oxygen demand

Answer 2

1. myocardial wall tension
2. myocardial contractility
3. heart rate

Question 3

large conductance vessels providing blood flow to myocardium with little role in vascular regulation

Answer 3

epicardial arteries (arise from aorta)

Question 4

What layers are present in epicardial arteries?

Answer 4

thin intima, smooth muscle media, and supportive adventitia

Question 5

What is the site of angioplasty or bypass?

Answer 5

epicardial arteries

Question 6

What artery provides diagonal and septal branches to the heart?

Answer 6

LAD

Question 7

Which artery provides obtuse marginal branches to the heart?

Answer 7

left cx

Question 8

Which vessels are responsible for the majority of coronary vascular resistance?

Answer 8

intramyocardial coronary arteries

Question 9

Is blood flow to the heart regulated at the microcirculation level or at the major epicardial level?

Answer 9

microcirculation

Question 10

For the heart, coronary blood flow is determined by the _____ into the coronary arteries and by the ______ of the coronary arterial system.

Answer 10

driving pressure and vascular resistance

Question 11

What parameters define coronary perfusion pressure?

Answer 11

central aortic pressure - LVEDP

Question 12

Does most of coronary blood flow occur during systole or diastole?

Answer 12

diastole –> because myocardial compressive forces prevent blood flow during systole

Question 13

compressive force applied to coronary arteries during systolic muscular contraction of the heart, limiting most flow to the diastolic period

Answer 13

extravascular resistance –> if heart rate increases, there is less diastolic time for delivery and less oxygen for the heart

Question 14

Are extravascular compressive forces greater on the subendocardial or subepicardial regions of the heart?

Answer 14

subendocardial –> net driving force of subendocardial blood flow is lower than for epicardium –> makes endocardium more vulnerable to ischemia

Question 15

Can resting or maximal coronary flow be maintained despite substantial epicardial stenosis?

Answer 15

yes

Question 16

The amount by which resistance can be decreased, therefore preserving flow in the setting of epicardial stenosis.

Answer 16

vasodilatory reserve

Question 17

Resistance changes that keep flow constant in face of altered pressure

Answer 17

autoregulation

Question 18

How is vasodilatory reserve described in a two resistor model?

Answer 18

R1 = resistance of epicardial vessels
R2 = resistance of small arteries (high but low impact)
Q = P/(R1+R2) --> if R1 increases due to stenosis, R2 will decrease to maintain constant flow

Question 19

How do vasodilation and vasoconstriction differ in regulation within the concept of myogenic regulation as it relates to coronary arteries?

Answer 19

constriction is via stretch induced depolarization of VSMCs

dilation is via potassium ion efflux through ATP-sensitive potassium channels

Question 20

What is the difference between endothelium dependent vasodilation and endothelial independent vasodilation as it relates to coronary arteries?

Answer 20

endothelium dependent requires intact endothelium –> NO release
endothelium independent does not require intact endothelium –> exogenous nitroglycerin, papavarine, calcium channel antagonists

Question 21

If you inhibit NO synthase under basal conditions, what is the consequence?

Answer 21

moderate vasoconstriction

Question 22

How does metabolic demand affect vascular resistance?

Answer 22

adenosine released from breakdown of ATP –> results in vasodilation/increase coronary blood flow via cAMP

Question 23

Is metabolic regulation of vascular resistance endothelium dependent/independent?

Answer 23

independent

Question 24

What is the difference between beta 1 and 2 adrenergic vasodilatory effects ?

Answer 24

1: via increased metabolic demand
2: via direct vasodilatory effect

Question 25

T/F endothelial dysfunction is a hallmark of early and late CAD and may be identified before critically important coronary narrowing is seen

Answer 25

T

Question 26

Can endothelial dysfunction be modified through standard treatments for CAD like lipid lowering and exercise?

Answer 26

yes

Question 27

What causes angina pectoris? How is it treated?

Answer 27

narrowing of one or more coronary arteries –> symptoms appear after 70% stenosis b/c of adequate compensation by small arterioles

tx = nitrates, anti-platelets, beta blockers, ultimately stent or CABG

Question 28

What causes unstable angina? How is it treated?

Answer 28

clinical syndrome of progressive chest pain –> often due to secondary rupture of atherosclerotic plaque w/in vessel resulting in platelet aggregation, thrombus formation, vasospasm

tx = nitrates, anti-thrombotics, platelet inhibitors, revascularization stent or CABG

Question 29

What causes acute MI? How is it treated?

Answer 29

plaque rupture and secondary thrombus/platelet accumulation resulting in complete/nearly complete occlusion of a coronary vessel

tx = stent, thrombolytic medifications to restore blood flow

Question 30

What causes coronary artery spasm? How is it treated?

Answer 30

severe, focal, reversible narrowings in epicardial arteries sometimes in presence of pre-existing atherosclerotic plaque

tx= nitrates, calcium channel blockers to prevent spasm

Question 31

What causes small vessel disease?

Answer 31

poorly defined syndrome with angina w/o obvious narrowing of epicardial arteries but with decreased vasodilator reserve