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CV > Coronary Arteries > Flashcards

Coronary Arteries Flashcards

1
Q

The right coronary artery is dominant is what percentage of people?

A

In 85% of individuals, the RCA supplies the posterior descending artery (PDA)

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2
Q

The left main coronary artery divides into what?

A
  • Left anterior descending (LAD): widow maker
  • Left circumflex

-Ramus intermedius
In 37% of people there is a trifurcation of left main

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3
Q

What is normal coronary blood flow?

A

70mL/100grams

About 5% of CO

Bulk of coronary blood flow is during diastole

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4
Q

What contributes most to the coronary vascular resistance?

A

Intramyocardial vessels

The epicardial conductance vessels are larger and on the surface. Only contribute a small percentage of resistance normally

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5
Q

What is the main determinant of myocardial oxygen supply?

A

Metabolic activity

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6
Q

How does a faster HR affect coronary blood flow?

A

A faster HR shortens diastole which decreases the amount of time for coronary blood flow

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7
Q

Which organ uses the most O2 while at rest?

A

Cardiac muscle: 9.7mL/100g/min

Next closest is kidneys at 6.0mL/100g/min

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8
Q

What is coronary perfusion pressure

A

Pressure gradient that drives blood though the coronary circulation

Coronary perfusion pressure =

DBP-LVEDP (or PCWP)

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9
Q

T/F: The heart extracts O2 to a greater extent than any other organ

A

True

Coronary sinus pO2 is normal 20-22mmHg (%sat 32-38)
-this is where 75% of venous return from myocardium goes

Bc can’t extract more O2, if there is an increase in demand, must increase coronary blood flow

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10
Q

Increased O2 demand results in lower tissue O2 tension. This causes _________

A

Vasodilation and increased blood flow

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11
Q

What is autoregulation?

A

Ability of a vascular network to maintain constant blood flow over a range of arterial pressures

It is an independent determinant of CBF

The set point at which CBF is maintained depends on MVO2

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12
Q

What is the most important endothelial method for controlling coronary vascular tone?

A

Nitric oxide —->cGMP

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13
Q

Damage to endothelial cells will lead to?

This will ultimately cause?

A
  • decreases Nitric Oxide and Prostacyclin production
  • Increased Endothelin production
  • vasoconstriction
  • vasospasm
  • thrombosis
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14
Q

Coronary blood flow is controlled predominantly by what 3 factors?

A
  1. Local metabolic
  2. Autoregulatory
  3. Endothelial
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15
Q

Sympathetic stimulation releases what from the sympathetic nerves and adrenal medullae to increase HR and contractility?

A

Epi

Epi and norepinephrine

*Increases the rate of metabolism of the heart
Direct effect

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16
Q

This is an indirect effect of increasing the rate of metabolism of the heart

A

Blood flow increases in proportion to the metabolic needs of the heart muscle

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17
Q

Vagal stimulation releases what which slows the heart and has a slight depressive effect on heart contractility?

A

Acetylcholine

These effects decrease cardiac O2 consumption and therefore indirectly constrict the coronary arteries
Contrast

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18
Q

During sympathetic stimulation, epi and norepinephrine

Do what to alpha and beta receptors in coronary vessels?

A

Alpha: constrict coronary vessels
(Larger vessels have more alpha)

Beta: dilate coronary vessels
(Smaller vessels have more Beta)
-Beta 1: in conduit arteries
-Beta 2: in resistance arteries

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19
Q

During parasympathetic stimulation, acetylcholine does what?

A

Vasodilation in healthy subjects

Vasoconstriction in pts with atherosclerosis (occurs once endothelial layer is damaged)

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20
Q

Because of __________. ________ the endocardium is more susceptible to ischemia, especially at lower perfusion pressure

A

Extravascular compression

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21
Q

The effect of extravascular compression is felt most at what point of the cardiac cycle?

A

Early systole

Bc aortic pressure, which is the main force maintaining vascular patency, is at a low point

22
Q

Systolic blood flow constitutes a much greater proportion of total blood flow to what area of the heart and why?

A

The right ventricle

Due to lower pressures generated by thin right ventricle in systole

23
Q

What are the subendocardium and subepicardial layer?

A

Subendocardium: inner layer of myocardium

Subepicaridal: outer layer of myocardium

24
Q

Extravascular compressive forces are greater in the inner or outer layer?

A

Inner layer

25
Q

Which layer of the myocardium is more susceptible to ischemia?

A

Subendocardial layer

26
Q

Epicardial coronary stenoses are associates with what?

A

Reductions in the subendocardial to subepicaridal flow ratio

Normal ratio is 1.25:1

27
Q

In the absence of CAD, maximal flow is ________x as great as at rest

A

4-5

Coronary flow respecter decreases with increasing severity of CAD

28
Q

Myocardial O2 consumption is defined as

A

The volume of O2 consumed per minute

(Usually expressed per 100g of tissue weight)

A resting heart uses 8mLO2/min per 100g

29
Q

Factors that increase myocardial O2 consumption

A
  • increased HR main one
  • increased inotropy
  • increased afterload
  • increased preload affects least
30
Q

Is pressure of volume work more costly regarding oxygen cost of myocardial work?

A

Pressure work

31
Q

Myocardial ischemia upsets the balance of what electrolytes?

A

Na and K

There is a decrease in Na-k ATPase activity which leads to an increase in intracellular Na, a decreased Na/Ca exchanged, and an overload of intracellular CA++

This leads to impaired contractility and eventually cell death

32
Q

There is an intracellular overload of what electrolyte during myocardial ischemia

A

Calcium

33
Q

Systolic dysfunction

A

Ischemia causes alterations that may range from minimal impact to absence of movement (akinesis) to systolic lengthening and post-systolic shortening (dyskinesia)

34
Q

In left ventricular failure, the flow volume loop moves what direction?

A

Narrows and moves to the right

35
Q

How does left ventricular failure affect the frank-starling curve?

A

EDP increases, but stroke volume goes down

36
Q

What are key features of a healthy heart?

A

Normal heart structure
Normal heart function
Fatty acid oxidation

37
Q

What are key features of compensated hypertrophy?

A
  • LV hypertrophy and thickening
  • Alterations in Ca++ handling
  • Switch to glucose utilization
  • Fibrosis
38
Q

What are key features of decompensated hypertrophy and heart failure?

A
  • LV dilation
  • cardiac dysfunction
  • apoptosis
  • EKG changes
  • excessive fibrosis
  • inadequate angiogenesis
  • excessive autophagy
  • energy deplete
39
Q

Diastolic dysfunction

A

When a sufficient amount of myocardium is rendered ischemic, LVEDP rises

Relaxation is impaired and myocardial compliance decreases

40
Q

What are the 4 phases of diastolic dysfunction and which is irreversible?

A
  1. Impaired relaxation
  2. Pseudonormalization
  3. Restrictive filling (reversible)
  4. Restrictive filling (irreversible)
41
Q

What does the flow volume look like with left ventricular diastolic failure?

A

Smaller and shift to the left

42
Q

Myocardial stunning

A

After a brief episode of severe ischemia, prolonged myocardial dysfunction with gradual return of contractile activity occurs

*duration of reduced performance is dependent on duration of ischemia. Reversible

43
Q

Myocardial hibernation

A

Presence of impaired resting LV function, owing to reduced CBF that can be restored toward normal by revascularization

*seen in chronic ischemia

44
Q

What are some things that can result from myocardial ischemia?

A 
Systolic/diastolic dysfunction
Angina
CHF/pulmonary edema
Arrhythmias
MI
Ventricular rupture or VSD
Cardiogenic shock
Death
45
Q

Drugs used to treat ischemia

A 
O2
Beta-blockers
Nitrates
Antiplatelet/anticoagulant
Analgesics 
Calcium-channel blockers
46
Q

What interventions can be done to treat myocardial ischemia?

A

CABG
-gold standard

Percutaneous coronary interventions

  • coronary balloon angioplasty
  • bare-metal coronary stents
  • drug-eluding stents
47
Q

How long should you wait before doing elective surgery after PCI?

A

Bare metal stent
-cardiac complications are lowest after 90 days

Drug-eluting stent
-1 year is recommended

48
Q

Name some examples of perioperative medical therapy

A 
Volatile anesthetic agents
-anesthetic preconditioning
Beta-blockers
Statins
-stabilize plaque
-anti-inflammatory
Alpha-2 agonists
-clonidine
-useful in pts not able to take beta-blockers (asthmatics_
calcium channel blockers
nitroglycerin
-use prophylactically unclear if changed in outcome
49
Q

Collateral blood flow

A

Develop in response to impairment of coronary blood flow

Develops between occluded and non-occluded branches

Originate from pre-existing arteries that undergo proliferation changes of the endothelium and smooth muscle

50
Q

Ischemic preconditioning

A

Brief periods of ischemia can be protective agains a subsequent prolonged ischemic insult

  • inhaled agents have effects that mimic IPC
  • K+ATP channels play an important role

CV (8 decks)

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