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physiology IV > Coronary Circulation > Flashcards

Coronary Circulation Flashcards

1
Q

What are the two major arteries of the heart?

A

The right coronary and the Left coronary

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2
Q

What is a major branch of the right coronary?

A

acute marginal

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3
Q

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

A

1- LAD
2- Circumflex artery
3- Ramus intermedians

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4
Q

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

A

It is predominantly to the right atrium via the coronary sinus

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5
Q

What are thebesian vessels?

A

vessels connecting cardiac chambers to arterioles, capillaries and venules

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6
Q

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

A

The Right Atrium

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7
Q

What are the three normal anatomical varients?

A

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

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8
Q

Is there any interconnectivity between coronary vessels?

A

Yes

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

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9
Q

Is coronary circulation a simple loop?

A

No, it is not….interconnections are present

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10
Q

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

A

the section between the anterior and posterior papilary muscle

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11
Q

What does the LAD supply?

A

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

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12
Q

What does the right coronary artery supply?

A

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

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13
Q

Failure of the papilary muscle results in what?

A

It results in acute mitral regurgitation and pulmonary edema

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14
Q

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

A

coronary circulation

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15
Q

When does coronary perfusion occur?

A

It occurs during diastole

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16
Q

Where and when does maximum flow occur?

A

Maximum flow occurs in the left coronary artery during early diastole

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17
Q

Perfusion = ?

A

blood flow (Q)

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18
Q

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

A

Nearly all of the oxygen delivered to it

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19
Q

Coronary blood flow is determined by:

A

1) the driving pressure through the coronary vessel

2) the resistance of the coronary vessels

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20
Q

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

A

Increasing Pressure erults in increasing perfusion

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21
Q

What is autoregulation?

A

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

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22
Q

What is coronary flow reserve?

A

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

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23
Q

What causes a reduction in coronary flow reserve?

A

epicardial coronary artery stenosis or coronary microvascular dysfuction

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24
Q

What impairs autoregulation?

A

1- critical fall in aortic pressure

2- chronic hypertension and LV hypertrophy

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25
Q

What are the two general mechanisms of autoregulation?

A

1- Metabolic mechanisms

2- Myogenic mechanisms

26
Q

What are some metabolic mechanisms for autoregulation?

A
  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
Q

What is an example of myogenic control in autoregulation?

A

arteriolar VSM contracts with increased intraluminal pressure

28
Q

What are some powerful vasodilators that endothelium produces?

A

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

29
Q

What are some risk factors associated with impaired endothelium dysfunction?

A 
1- Hypertension
2- Diabetes mellitus
3- Smoking
4- Menopause
5- Dense LDL
6- Aging
7- Hyperhomocystenemia
30
Q

How is NO produced?

A

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

31
Q

What stimulates NO production?

A

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
Q

What can inhibition of NO cause?

A

Inhibition of NO can cause vasoconstriction

33
Q

What is preload?

A

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

34
Q

What is afterload?

A

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

35
Q

What is a major determinant of coronary blood flow?

A

mixed venous oxygen saturation (MVO2)

36
Q

Do preload and afterload influence MVO2?

A

yes

37
Q

What pathologies influence preload?

A

Mitral valve stenosis, mitral valve regurgitation, aortic insufficiency

38
Q

What pathologies influence afterload?

A

aortic stenosis, HNT

39
Q

What are four pathologies that e?ffect MVO2

A

CAD, Ventricular hypertrophy, Ventricular dilation,

Coronary fistula

40
Q

What is the definition of ischemia?

A

imbalance between myocardial oxygen supply and demand

41
Q

Describe supply ischemia:

A

Increased coronary vascular tone
Intracoronary platelet aggregation
Thrombus formation

42
Q

What are three general examples of ischemia?

A

Supply ischemia, demand ischemia, hypoxia

43
Q

What is the definition of demand ischemia?

A

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

44
Q

What maintains constant flow with increasing stenosis severity?

A

autoregulation

45
Q

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

A

it reduces coronary flow reserve

46
Q

Does myocardial mass increase or decrease with Left Ventricular hypertrophy?

A

It increases

47
Q

What are three ways to assess coronary blood flow?

A

coronary angiogram, magnetic resonance angiogram, computed tomography angiogram

48
Q

What are some pharmacologic methods of improving coronary blood flow?

A

Nitroglycerine, adenosime

49
Q

What are two invasive methods of improving coronary blood flow?

A

angioplasty (with stent) and CAGB

50
Q

What are the limitations of angioplasty?

A

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

51
Q

What are some pharmacological vasodilators?

A

Nitroglycerine, dipyridamole, papaverine, adenosine, NO

52
Q

What are the three main mechanisms of nitroglycerine?

A

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
Q

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

A

dipyridamole

54
Q

What type of cells can release adenosine?

A

cardiac myocytes

55
Q

Does adenosine have a direct effect on larger arteries?

A

No

56
Q

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

A

Nitric oxide synthase

57
Q

Is NO produced intermittently or continually?

A

Continually

58
Q

What stimulates NO formation?

A

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

59
Q

What does inhibition of NO cause?

A

vasoconstriction and reduction in the magnitude of metabolic dilation

60
Q

Does hypoxia increase or decrease the production of NO?

A

increase production

61
Q

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

A

1- reduction of afterload

2- diastolic augmentation

62
Q

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

A

Increase it about their natural threshold

physiology IV (40 decks)

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