Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physio: Cardiovascular > Coronary Circulation > Flashcards

Coronary Circulation Flashcards

1
Q

What are the major branches of the coronary arteries?

A
  • Right coronary artery: has PDA branch in 80% of people
  • Left coronary artery: bifurcate to LAD with diagonal branches and left circumflex with obtuse marginals
    • in 37% of population ramus intermedius trifurcates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the ramus intermedius? In what percentage of the population does it exist?

A

37%

It’s an additional branch in people who have a trifurcation in the left main coronary artery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Do the major epicardial arteries contribute significantly to coronary vascular resistance?

A

No
Only contribute a small % of resistance, but intramyocardial arterioles contribute most to total coronary vascular resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is capillary density? Is capillary density increased or decreased in the myocardium?

A

A high capillary-to-cardiomyocyte ration—> shortens diffusion distance and ensures adequate O2 delivery/waste removal
- capillary density is increased in the myocardium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the major determinants of myocardial oxygen demand?

A

HR
Contractility
Systolic wall tension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the major determinants of myocardial oxygen supply?

A
  • vascular resistance
  • coronary blood flow
  • O2 carrying capacity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Is resting O2 consumption of the heart high or low relative to other organs in the body?

A

High—> 75% of O2 delivered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the formula for coronary perfusion pressure?

A

Coronary perfusion pressure= DBP - LVEDP (or PCWP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Is O2 highly extracted from blood flowing through the heart?

A

Yes, the heart extracts O2 to a greater extent than any other organ
- increased O2 demand must be met by increasing coronary blood flow (can only minimally increase O2 extraction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What factors control coronary blood flow?

A
  • Metabolic control
  • autoregulation: 50-150 for MAP
  • endothelial control of vascular tone
  • extravascular compressive forces
  • neural control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Does the majority of coronary blood flow occur during systole or diastole in the left ventricle? Why?

A
  • diastole: extravascular compression of cardiac muscle squeezing during systole decreases blood flow drastically
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which layer of the myocardium is at greatest risk for ischemia?

A

Subendocardium (inner layer)d/t extravascular compression, especially at low perfusion pressures
- not as affected during diastole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is coronary flow reserve?

A

Maximal flow capacity - baseline blood flow
—> difference between baseline blood flow and maximal blood flow
- usually max flow is 4-5 times greater than at rest
- reserve decreases with CAD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Which of the following places a greater O2 cost on the heart? Pressure work vs volume work

A

Pressure work is more costly since it increases after load and makes the heart work much harder

  • pressure work: increased arterial pressures at constant CO (very hard with tachycardia too)
  • volume work: increasing CO while maintaining constant pressure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How stenotic do coronary vessels have to be before there is a significant decrease in flow?

A

Critical stenosis = 60-70% reduction in diameter of the large distributing artery
- coronary arteries ~75% stenosis is significant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the final intracellular ion disturbance that leads to impaired myocardial contraction and cell death?

A

Decreased Na/Ca exchange causes intracellular Ca++ overload, which causes impaired myocardial contraction and CELL DEATH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the effects of myocardial ischemia on systolic function?

A

Loss of inotropy**
- causes downward starling curve—> results in decreased stroke volume and compensatory increase in preload, because of incomplete ventricular emptying
—> increase in EDV and pressure eventually dilates the ventricle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the effects of myocardial ischemia on diastolic dysfunction?

A

LVEDP rises, relaxation is impaired
Myocardial compliance decreases
Ventricular hypertrophy
* impairs the heart’s ability to relax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is myocardial stunning?

A

Occurs after brief episode of severe ischemia

  • prolonged myocardial dysfunction with gradual return of contractile activity
  • completely reversible
  • less responsive to inotropy—> can result in cardiogenic shock
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is myocardial hibernation?

A

Regional cardiac dysfunction d/t chronic ischemia

- impaired resting LV function —> if coronary blood flow is restored the region will regain normal function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are some of the consequences of myocardial ischemia?

A
  • systolic and diastolic dysfunction
  • angina
  • CHF or pulmonary edema
  • arrhythmias
  • MI
  • ventricular rupture or VSD
  • cardiogenic shock
  • death
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are some drugs used for the treatment of ischemia?

A
  • O2
  • Ăź- blockers: blunt SNS
  • nitrates: decrease SVR—> vasodilation
  • anti-platelet/anti-coags.
  • analgesics: morphine
  • Ca++ channel blockers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are some of the interventions used in the treatment of ischemia?

A
  • CABG
  • percutaneous coronary intervention
    • ballon angioplasty
    • bare metal or drug eluding stents
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How long should you wait before doing elective surgery on a patient who has had a drug eluting stent placed?

A
  • drug eluting stent: waiting 1 year is recommended d/t stopping anticoagulation meds
  • bare metal stent: cardiac complications are lowest after 90 days
25
Q

What are some of the drugs that are used to reduce cardiac ischemic events during surgery?

A
  • volatile anesthetics—> anesthetic preconditioning
  • Ăź-blockers: have pt continue taking
  • statins: stabilize plaque
  • anti-inflammatory
  • alpha - 2 agonists
  • Ca++ channel blockers
26
Q

Is isoflurane an appropriate agent to use during cardiac surgery? Why or why not?

A

Yes

Minimal cardiac effects

27
Q

What are collateral blood vessels in the heart? How are they formed?

A

In response to chronic slow developing occlusion—> new vessels for between branches of occluded and non-occluded arteries

  • originate from pre-existing arterioles that undergo changes of endothelium and smooth muscle
    • vascular endothelial growth factor
    • monocytes chemoattractive protein
28
Q

What is anesthetic preconditioning in the heart?

A

Anesthetics have effect that mimics ischemic preconditioning

- K+ atp channels play an important role

29
Q

What parts of the heart does the LCA supply?

A

Anterior and left lateral portion of the LV

30
Q

What part of the heart does the right coronary artery supply?

A

Most of RV and posterior part of the heart in 80-90% of people

31
Q

Where does 75% of total coronary blood flow from the heart muscle return to?

A

The coronary sinus

32
Q

How is the remaining coronary blood returned to the heart?

A

Small anterior cardiac veins that flow directly into the RA
- a very small amount of RV blood blows back to heart through tiny thespian veins that empty into all chambers of the heart

33
Q

What is normal coronary flow and how does it change during exercise?

A

Normal coronary flow is ~225 mL/min (4-5% of CO

- increases 3-4 fold during exercise

34
Q

Epicardial coronary arteries supply most of the muscle of the heart.
T/F

A

True

35
Q

In all vascular bed (including heart tissue), where are the primary sites of vascular resistance?

A

Small arteries and arterioles

—> primary site for regulation of blood flow

36
Q

Does the heart utilize anaerobic metabolism?

A

The heart has very little capacity for anaerobic metabolism

  • normally it consumes lactate
  • myocardial lactate production is a sign of severe ischemia
37
Q

What percent of O2 delivered to the heart does it consume at rest?

A

75%

- has no significant reserve because of this

38
Q

How many mL/min of blood does cardiac muscle consume?

A

9.7mL/100G/min blood

39
Q

Blood flow through coronary system is regulated mostly by what?

A

Local arterial vasodilation in response to needs of cardiac muscle

  • as need increases, flow increases
  • as need decreases, flow decreases
40
Q

Coronary circulation is exquisitely sensitive to __________________________________.

A

Myocardial O2 tension

41
Q

Increasing O2 demand results in higher or lower tissue O2 tension?

A

Lower

42
Q

How does low tissue O2 tension cause vasodilation and increased blood flow?

A

From the release of:

  • adenosine
  • nitric oxide
  • prostaglandins
  • K+ atp channels
43
Q

Damage to endothelial cells leads to:

A
  • decreased NO and prostacyclin production (stops vasodilation)
  • increased endothelium production—> vasoconstriction
  • Will lead to vasoconstriction, vasospasm, thrombosis **
44
Q

What are the different effects of neural control?

A
  • direct effects: SNS stimulation, epi and norepinephrine—> increaseHR, inotropy and cardiac metabolism
  • indirect: dilates coronary vessels increasing flow(since metabolism increases)
  • contrast: vagal stimulation (from acetylcholine release) slows HR, slight decrease in inotropy
    • decreases O2 consumption- indirectly constricts coronary arteries
45
Q

What are the constrictor receptors?

What are the dilator receptors?

A

Constrictor: alpha receptors
Dilator: beta receptors

46
Q

What is one of the worst things you can do to a pt with severe CAD?

A

Cause tachycardia—> they have no reserve

47
Q

What does O2 consumption mean?

A

Volume of O2 consume/min/100g of tissue

48
Q

What is meant by wall tension?

A

Tension generated by myocytes that results in given intravascular pressure at a particular ventricular radius
- late of la place explains wall tension. Pr/n

49
Q

What are 2 settings that lead to myocardial supply and demand mismatch?

A
  • profoundly low perfusion pressures

- irreversible stenosis

50
Q

What are factors that increase myocardial O2 consumption?

A
    • # 1 is tachycardia
  • increased inotropy
  • afterload
  • preload (to a lesser extent than the others)
51
Q

What is unstable angina caused by?

A

Thrombosis

52
Q

What is meant by stenosis?

A

Abnormal narrowing of an artery or decreased cross sectional area of heart valve when opened

53
Q

According to Pousielles law, decreasing the radius by 1/2 will increase resistance by _______.

A

16 fold

54
Q

What do Ăź-blockers do?

A

Block sympathetic Ăź-adrenergic receptors, preventing increase in HR and cardiac metabolism
- decreases cardiac need for extra O2 during “stressful” conditions

55
Q

What do Ca++ channel blockers do?

A

Vasodilation: increases coronary blow

Decrease HR

56
Q

What happens if a CABG is done before severe damage occurs? After?

A

If a CABG done before severe damage occurs—> may provide pt with normal survival expectation
- if done after severe damage occurs the CABG is likely to be of little value

57
Q

What to drug eluting stents do?

A

Slowly release drug and may help prevent excess growth of endothelial scar tissue that causes restenosis

58
Q

What is myocardial preconditioning?

A

Phenomenon where an intervention or trigger before a prolonged ischemic insult to myocardium results in decrease in the infarcted area

Physio: Cardiovascular (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions