Coronary Circulation Flashcards Preview

physiology IV > Coronary Circulation > Flashcards

Flashcards in Coronary Circulation Deck (62):
1

What are the two major arteries of the heart?

The right coronary and the Left coronary

2

What is a major branch of the right coronary?

acute marginal

3

What are the major branches of the left main coronary artery?

1- LAD
2- Circumflex artery
3- Ramus intermedians

4

Venous drainage of the myocardium is predominantly to the ________________ via the _______________.

It is predominantly to the right atrium via the coronary sinus

5

What are thebesian vessels?

vessels connecting cardiac chambers to arterioles, capillaries and venules

6

Which chamber of the heart recieves the majority of thebesian drainage?

The Right Atrium

7

What are the three normal anatomical varients?

1- coronary dominance
2- single ostia
3- extra ostia

8

Is there any interconnectivity between coronary vessels?

Yes

1- arterial to venous shunts
2- arerial to arterial connections
3- venous to venous connections

9

Is coronary circulation a simple loop?

No, it is not....interconnections are present

10

What section of the left ventricle free wall is supplied by the left circumflex?

the section between the anterior and posterior papilary muscle

11

What does the LAD supply?

The free wall of the LV, the anterior 2/3 of the ventricular septum and a small portion of the free wall of the RV

12

What does the right coronary artery supply?

the free wall of the RV, the posterior 1/3 of the interventricular septum and the posterior wall of the Left ventricle to the posterior papilary muscle

13

Failure of the papilary muscle results in what?

It results in acute mitral regurgitation and pulmonary edema

14

What protects against papilary muscle failure resulting from ischemic heart disease?

coronary circulation

15

When does coronary perfusion occur?

It occurs during diastole

16

Where and when does maximum flow occur?

Maximum flow occurs in the left coronary artery during early diastole

17

Perfusion = ?

blood flow (Q)

18

How much oxygen does the myocardium extracts from coronary blood flow?

Nearly all of the oxygen delivered to it

19

Coronary blood flow is determined by:

1) the driving pressure through the coronary vessel
2) the resistance of the coronary vessels

20

How does P (Pressure) influence Q (Perfusion)?

Increasing Pressure erults in increasing perfusion

21

What is autoregulation?

Autoregulation is the intrinsic ability of the heart to maintain a constant blood flow over a wide range of coronary perfusion pressures.

22

What is coronary flow reserve?

the maximal increase in coronary blood flow above its resting level for a given perfusion pressure when coronary vasculature is maximally dilated

23

What causes a reduction in coronary flow reserve?

epicardial coronary artery stenosis or coronary microvascular dysfuction

24

What impairs autoregulation?

1- critical fall in aortic pressure
2- chronic hypertension and LV hypertrophy

25

What are the two general mechanisms of autoregulation?

1- Metabolic mechanisms
2- Myogenic mechanisms

26

What are some metabolic mechanisms for autoregulation?

1. result of local metabolism
2. may be due to NO mediated dilation
3. endothelium senses changes in pressure through pressure-sensitive ion channels

27

What is an example of myogenic control in autoregulation?

arteriolar VSM contracts with increased intraluminal pressure

28

What are some powerful vasodilators that endothelium produces?

1- Endothelium derived relaxing factor (EDRF)
2- NO
3-Prostacyclin
4- Endothelium derived hyperpolarizing factor (EDHF)

29

What are some risk factors associated with impaired endothelium dysfunction?

1- Hypertension
2- Diabetes mellitus
3- Smoking
4- Menopause
5- Dense LDL
6- Aging
7- Hyperhomocystenemia

30

How is NO produced?

From the amino acid L-arginine by the enzymatic action of nitric oxide synthase (NOS) in the vascular endothelium

31

What stimulates NO production?

Increased blood flow stimulates NO formation (flow-dependent NO formation) because shear force on the vascular endothelium causes a release of calcium and cNOS activation.

32

What can inhibition of NO cause?

Inhibition of NO can cause vasoconstriction

33

What is preload?

The filling pressure (the amount of stretch on muscle just before contraction)

34

What is afterload?

This is the pressure/ resistance the heart is working against while it is squeezing

35

What is a major determinant of coronary blood flow?

mixed venous oxygen saturation (MVO2)

36

Do preload and afterload influence MVO2?

yes

37

What pathologies influence preload?

Mitral valve stenosis, mitral valve regurgitation, aortic insufficiency

38

What pathologies influence afterload?

aortic stenosis, HNT

39

What are four pathologies that e?ffect MVO2

CAD, Ventricular hypertrophy, Ventricular dilation,
Coronary fistula

40

What is the definition of ischemia?

imbalance between myocardial oxygen supply and demand

41

Describe supply ischemia:

Increased coronary vascular tone
Intracoronary platelet aggregation
Thrombus formation

42

What are three general examples of ischemia?

Supply ischemia, demand ischemia, hypoxia

43

What is the definition of demand ischemia?

Increase in coronary blood flow that is insufficient to meet the increase myocardial O2 demand

44

What maintains constant flow with increasing stenosis severity?

autoregulation

45

What is the effect of ventricular hypertrophy on coronary flow reserve?

it reduces coronary flow reserve

46

Does myocardial mass increase or decrease with Left Ventricular hypertrophy?

It increases

47

What are three ways to assess coronary blood flow?

coronary angiogram, magnetic resonance angiogram, computed tomography angiogram

48

What are some pharmacologic methods of improving coronary blood flow?

Nitroglycerine, adenosime

49

What are two invasive methods of improving coronary blood flow?

angioplasty (with stent) and CAGB

50

What are the limitations of angioplasty?

Invasive, potential underestimation of lesion severity, no information on hemodynamic significance, no information on vessel wall

51

What are some pharmacological vasodilators?

Nitroglycerine, dipyridamole, papaverine, adenosine, NO

52

What are the three main mechanisms of nitroglycerine?

1-Dilates epicardial conduit arteries and small coronary resistance vessels

2-Improves subendocardial perfusion by reducing LV end-diastolic pressure by venodilation

3-Dilates coronary collateral vessels

53

These three facts describe what vasodilator?

1-Inhibits the myocyte reuptake of adenosine released locally

2-Mechanism of action similar to adenosine

3-Reversed by adenosine receptor antagonists---aminophylline

dipyridamole

54

What type of cells can release adenosine?

cardiac myocytes

55

Does adenosine have a direct effect on larger arteries?

No

56

What enzyme is needed in the synthesis of NO from L- arginine?

Nitric oxide synthase

57

Is NO produced intermittently or continually?

Continually

58

What stimulates NO formation?

Increased blood flow, because shear force on the vascuar endothelium causes a release of calcium and cNOS ativation

59

What does inhibition of NO cause?

vasoconstriction and reduction in the magnitude of metabolic dilation

60

Does hypoxia increase or decrease the production of NO?

increase production

61

How does the intra aortic balloon pump (a cardiac assist device? improve cardiac function?

1- reduction of afterload

2- diastolic augmentation

62

How does cardioplegic solution effect resting membrane potential of the myocytes?

Increase it about their natural threshold