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Evaluation of the Cardiac System > Coronary Hemodynamics and FFR > Flashcards

Coronary Hemodynamics and FFR Flashcards

1
Q

What is CFR?

A

Coronary Flow Reserve

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2
Q

What controls coronary blood flow?

A

Local metabolites such as adenosine or nitric oxide

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3
Q

What is the basic principle of FFR?

A

When resistance is constant, changes in pressure are proportional to changes in flow.

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4
Q

What does FFR correlate with?

A

Maximum myocardial blood flow in the presence of a stenosis divided by the theoretical maximum flow in a normal vessel.

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5
Q

How is FFR obtained?

A

Simultaneously measuring the mean aortic pressure and coronary pressure distal to the stenosis at hyperemia.

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6
Q

What is the FFR threshold that is used in clinical practice today?

A

0.80

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7
Q

What process are myocardial cell contraction and relaxations?

A

Aerobic processes that require oxygen

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8
Q

What are the determinants of myocardial oxygen demands? (5)

A

-Preload
-Afterload
-Heart rate
-Contractility
-Basal Metabolic Rate

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9
Q

What percentage does systolic wall tension use for myocardial oxygen demand?

A

30%

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10
Q

What affects wall tension? (4)

A

-Interventricular pressure
-Afterload
-End Diastolic Volume
-Myocardial Wall Thickness

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11
Q

What vessels are the first to branch off the aorta?

A

Coronary Arteries

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12
Q

What is the percentage of cardiac output when the body is at rest through the coronary arteries? (2)

A

5%
250 mL/min

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13
Q

Under basal conditions, the myocardium extracts approximately what percentage of delivered oxygen?

A

75%

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14
Q

The myocardium has a basal metabolic requirement that is what times that of resting skeletal muscle and what to that of skeletal muscle under sever acidotic conditions? (2)

A

-15 to 20 times
-Equal

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15
Q

What is coronary blood flow controlled primarily by?

A

Changes in resistance in the small arteries and arterioles.

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16
Q

When does coronary blood flow occurs?

A

During diastole

17
Q

Flow in the left coronary artery has what compared to the right coronary artery?

A

Greater diastolic predominance because of the compressive forces of the left ventricle

18
Q

What percentage of coronary flow in the left anterior descending artery occurs in diastole?

A

85%

19
Q

Right coronary artery blood flow is what in systole and diastole

A

More or less equal

20
Q

The predominance of flow during diastole does what during tachycardia?

A

Exacerbates myocardial ischemia

21
Q

With increased heart rates, oxygen supply is?

A

Reduced because diastole is shortened whereas demand increases

22
Q

What is autoregulation?

A

Hearts ability to maintain coronary blood flow in the presence of varying perfusion pressures

23
Q

Auto regulation maintains consistent coronary flow over a range of perfusion pressures from?

A

60 to 150 mm Hg

24
Q

In the setting of maximum vasodilation of coronary resistance vessels, blood flow is?

A

No longer autoregulated and varies linearly with perfusion pressure

25
Q

The ability to auto regulate to maintain flow when perfusion pressures are decreased are important in?

A

Presence of epicardial coronary stenoses

26
Q

What is the basic principle of Fractional Flow Reserve?

A

When resistance is constant, changes in pressure are proportional to changes in flow

27
Q

What enabled the introduction of the concept of pressure derived FFR?

A

A pressure transducer mounted on a 0.014 in angioplasty wire

28
Q

What does FFR correlate with?

A

Maximum myocardial blood flow in the presence of a stenosis divided by the theoretical maximum flow in a normal vessel

29
Q

FFR represents that fraction of?

A

Normal maximum flow that is achievable in the presence of epicardial coronary stenosis

30
Q

What is the measurement and clinical use of FFR depends on what two assumptions?

A

-Maximal Hyperemia in the target vessel has been obtained
-Negligible coronary venous pressure

31
Q

What is iFR?

A

Instantaneous wave-free ratio

32
Q

What is instantenous wave-free ratio iFR?

A

Measurement of the hemodynamic significance of a coronary artery stenosis which relies on comparison of pressures during diastole in the absence of hyperemia.

33
Q

When is iFR measured?

A

During the wave free period of mid to late diastole when flow during the cardiac cycle is highest and microcirculatory resistance is the lowest.

34
Q

During the period of iFR, what is related?

A

Pressure and flow velocity are linearly related, which allows pressure ratios to be used to determine the limitation to flow of a lesion

35
Q

What is not required in iFR unlike FFR assessment?

A

Hyperemia (thus adenosine) is not required

Evaluation of the Cardiac System (10 decks)

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