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Flashcards in Stable CAD Deck (49):
1

Clinical expression of stable ischemic heart disease reflects a...

imbalance between myocardial demand and supply of/for O2.

2

Myocardial Oxygen Supply based on

Blood O2 content (Hgb level and O2 sat)

Coronary Flow

3

What determines coronary flow

Directly related to perfusion pressure and indirectly related to vascular resistance.

4

Perfusion pressure

Coronary flow during diastole. Minimum diastolic pressure of 60-65 mmHg needed to ensure flow.

5

Conditions that reduce coronary flow

Things that lower diastolic pressure like aortic regurgitation or hypotension. Also if LVEDP is higher than normal (aortic regurg), gradient between aorta and LV is decreased and blood won't flow.

6

What controls coronary vascular resistance?

Vascular tone and degree of coronary stenosis.

7

Most important mediator of vascular tone?

Adenosine -- which is produced during hypoxemia and causes vessels to dilate causing increased coronary blood flow.

8

Do coronary vessels have alpha and beta receptors?

yes! B2 receptors

9

Endothelium dependent vasodilators

ACh, serotonin, shear stress. These things cause endothelium to release NO which causes vascular smooth muscle relaxation and increased blood flow. These things increase eNOS to create NO from L-arg. NO diffuses and promotes activity of GC, which increases cGMP, which causes vasodilation.

10

Endothelium dependent vasoconstrictors

Thrombin, ang II, epinephrine. Cause endothelin I to be released from endothelial cells which is a potent vasoconstrictor.

11

Normal, endothelium INdependent effect of ACh? ACh with normal/abnormal endothelium

Vasoconstrictor. But when given in the setting of normal endothelium, vascular smooth muscles dilate. However, in abnormal endothelium (increased number of risk factors) ACh causes vasoconstriction again.

12

Relationship between wall stress and myocardial oxygen demand

Increased wall stress (due to pressure/volume overload), increased myocardial demand. Wall stress = Pxr / 2h

13

What is worse, a thicker plaque causing lumen obstruction, or a longer plaque?

Thicker plaque. R = L / r^4

14

Relationship between stenosis and coronary flow at rest and during exertion.

During exertion, Coronary flow is maximal until about 70% stenosis. Before 70%, endothelial cells are able to compensate.

During rest, coronary flow is normal until about 93% occlusion. This is unstable angina.

15

What happens in endothelial cell dysfunction?

Release of endothelium-dependent vasodilators is impaired due to shear stress or other stimuli. Vasoconstricting effects of catecholemines predominate.

Loss of antithrombotic effect too, so thrombosis is more likely.

16

Are problems with coronary arteries worse in macro or microvasculature?

Microvasculature. There's so much that can't be seen on angiogram.

17

Non atherosclerotic myocardial ischemia caused by?

Reduced O2 supply (aortic regurg -- decrease in diastole, decrease in perfusion pressure), acute blood loss

Increased O2 demand (tachyarrhythmias like afib, hypertensive crisis which causes increased wall stress, severe aortic stenosis)

18

What are the sequellae of ischemia?

Myocyte necrosis

Myocyte stunning

Myocyte hibernation

19

Myocyte necrosis

Irreversible cell death. Can be detected by EKG by presence of Q wave, and by cardiac imaging.

20

Stunned myocardium

Systolic dysfunction after transient ischemia -- not necrosis. Function gradually recovers.

21

Hibernating myocardium

Chronic ventricular dysfunction due to chronic multivessel CAD. Need to revascularize to restore function, but function can be restored.

22

Stable angina

Retrosternal chest discomfort caused by exertion or emotional stress (increase BP increase contract, increase demand for O2)

23

Unstable angina

New-onset severe angina or increase in severity/frequency of previously stable symptoms. Plaque rupture leads to thrombosis reducing myocardial oxygen supply

24

Prinzmetal

Variant angina. Episodes of coronary spasm reducing oxygen supply. Tends to occur at rest.

25

Syndrome X

Chest pain, positive stress test, but normal coronary arteries. Pain.

Thought to be caused by microvascular dysfunction.

26

Silent ischemia

Ischemia that occurs without clinical symptoms.

27

Duration of stable angina

Few minutes. Happens for years

28

Quality of stable angina

Various presentations. Burning, pressure, tightness, heaviness

29

Differential for chronic stable angina

Pericarditis (sxs worse with dep inspiration or positional changes)
GI (reflux, peptic ulcer disease)
MSK (costochondritis)

30

ECG finding for ischemia

St segment depression

31

ECG finding for infarction

ST segment elevation

32

Is ECG normal for stable angina?

50% of the time

33

How else to test for angina?

Stress test. Look at EKG, do nuclear perfusion imaging

34

Angiography limitation

Only shows lumen. Not able to assess atherosclerosis in vascular wall.

35

Nitrates

Used for treatment of sxs in angina. Causes venodilation and reduction in LV volume, which lowers wall stress and myocardial oxygen demand.

Also vasodilates the coronary arteries, but this is less relevant because endothelial cells are already trying to maximally dilate.

No long term effect on survival

36

B-blockers for angina

Reduce myocardial oxygen demand by slowing HR and decreasing force of contraction.

Also increases duration of diastole, so can increase oxygen supply to myocardium.

Mortality benefit in patients with heart failure and MI.

37

CCB types

Dihydropyridines and non-dihydropyridines

38

Dihydropyridines and function

Amplodipine, nifedipine.

Vasodilate (decrease preload AND afterload) and decrease myocardial oxygen demand by reducing wall stress

39

Non-dihydropyridines

Diltiazem, verapimil

Cardiac suppressants, reduce HR and contractility. Lower oxygen demand.

Careful when combining with B blockers.

40

Ranazoline

Decreases anginal frequency, improves exercise tolerance, but unsure how. Maybe decreases diastolic dysfunction.

41

Aspirin for angina

Reduces risk of thrombotic complication by inhibiting platelet aggregation.

42

Clopidigrel (thienopyridine)

Inhibitors of platelet P2Y12 receptor. Antithrombotic, more powerful than aspirin. Don't combine them.

43

HMG-CoA reductase therapy

Statins. Lower risk for death/mi in patients with CAD. Give to all high risk patients.

44

Ace inhibitor for CAD

Reduce cardiac events like LV dysfunction, post MI.

45

Revascularization for CAD

Can be accomplished by stenting and/or coronary artery bypass graft.

46

Bare metal stents vs Drug eluting stents

Pros and cons

Bare metal stents cause intima proliferation around the stent, which is antithrombotic, but can result in restenosis.

Drug eluting stents inhibit restenosis, but increases the risk for thrombosis. Necessitates the use of long term dual antiplatelet therapy.

47

What did the courage trial reveal?

No reduction in death or MI with upfront PCI in addition to medical therapy.

So medical therapy first, then PCI.

48

Venous vs arterial bypass grafts

Venous graphs aren't as durable.

Arterial grafts have 90% patency at 10 years.

49

Is CABG or PCI better?

CABG mostly. Better for sicker patients.