Lecture 10: Ischemic Heart Disease

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95 Terms

1
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Coronary circulation supplies the heart with __ (2) to maintain adequate function.

oxygen & nutrients

2
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Coronary circulation must adapt to __ in the systemic metabolic needs.

rapid fluctuations

3
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Imbalance between myocardial oxygen demand and supply leads to: (3)

  • myocardial ischemia and contractile dysfunction

  • cardiac arrhythmia

  • myocardial infarction and possibly death

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What are the 2 main coronary arteries?

right coronary artery & left coronary artery (which includes left anterior descending artery & circumflex artery)

5
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Following a coronary artery occlusion, __ may occur beneath the __ surface & spread within the __.

necrosis; endothelial; myocardial tissue

6
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What is ischemia?

myocardial oxygen demand in excess of supply (demand is larger than supply)

7
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What is infarction?

continued ischemia leading to muscle damage

8
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Myocardial O2 __ depends on heart rate, contractility, and wall tension.

consumption

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Myocardial O2 consumption demand increases with factors that increase: (3)

  • rate

  • ionotropic stimuli (ca and catecholamines)

  • elevated aortic pressure

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Myocardial O2 supply depends on: (2)

  • coronary arterial and capillary inflow

  • O2 transport and delivery

    • needs adequate inspired O2 (amount of oxygen in blood is normal) and normal hemoglobin (to allow for effective oxygen transport)

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Coronary arterial and capillary inflow usually has [high/low] resistance unless __. The resistance is regulated by several factors, some dependent on __.

low; occluded; endothelial cells

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Vascular endothelium has important __ functions that promote __.

homeostatic; vasodilation

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How do vascular endothelium promote homeostasis? (2)

  1. sense mechanical forces and regulating vascular tone

  2. production of many other vasoactive substances (pro and anti-proliferative, pro and anti-thrombotic, and angiogenic factors)

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How does vascular endothelium regulate vascular tone?

  • vasodilators: endothelium-derived relaxing factor (EDRF), nitric oxide (NO), and prostacyclin

  • vasoconstrictors: endothelin 1 (ET-1), angiotensin II, thromboxane A2

15
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__ inhibits recruitment and differentiation of inflammatory cells by inhibiting __. This is a __ effect in the setting of ischemia.

NO; inflammatory cytokines; protective (prevents excessive inflammatory response that can damage tissues during a time with limited blood supply)

16
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What are the predisposing risk factors for ischemic heart disease? (3)

  1. age: inc risk as inc age

  2. sex: males > females, but more risk for females after menopause

  3. family history

17
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What are risk modulating behaviors for IHD? (behaviors that will increase risk) (5)

  1. smoking

  2. atherogenic diet

  3. alcohol intake

  4. lifestyle: physical activity

  5. personality type: hard to measure but data appears real

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What are some metabolic factors that increase risk of IHD? (7)

  1. HTN

  2. diabetes

  3. obesity

  4. metabolic syndrome

  5. dyslipidemia

  6. iron overload

  7. homocysteine excess

19
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Metabolic syndrome includes __ resistance and impaired __.

insulin; glucose tolerance

20
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The best predictor of atherosclerotic heart disease is total __ ratio.

cholesterol to HDL (ideal is 3.5 or lower)

21
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__ has antifibrinolytic properties. Elevation is strongly correlated with __.

lipoprotein (a); heart disease

22
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__ is protective, while __ is damaging

HDL; LDL

23
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__ occurs as a result of impaired plasma lipid control and is typically characterized by abnormal levels of lipoproteins.

Dyslipidemia

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__ facilitates LDL oxidation.

iron overload

25
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__ causes a direct toxic effect on endothelial cells, interference with clotting factors, and promotion of oxidation of LDL.

homocysteine excess

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__ can correct homocysteine excess.

folic acid

27
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Inflammation is emerging as an important __ for IHD.

risk factor

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__ is a marker of systemic inflammation.

C-reactive protein (CRP)

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CRP is produced by the __ and cells within the __.

liver; atheroma

30
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CRP is strongly correlated with the risk of: (4)

  • MI

  • stroke

  • peripheral arterial disease

  • sudden cardiac death

31
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__ can also be a risk factor for IHD, but the effect is weak.

plasma fibrinogen

32
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Label each of the following with inc/dec to determine how each would be a risk factor for IHD.

  • total cholesterol

  • LDL

  • lipoprotein a

  • homocysteine

  • CRP

  • fibrinogen

  • HDL

all inc except dec for HDL will put a person at higher risk for IHD

33
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__ are used to determine and diagnose a patient’s risk of coronary heart disease.

risk charts

34
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<p>What does this risk chart study show? </p>

What does this risk chart study show?

color- where risk is

highest risk = man who is smoker over the age of 70, high systolic pressure & high blood cholesterol

lowest risk = young man <30 y/o, nonsmoker, good BP, even with high BP if cholesterol is managed —> risk is same

  • if cholesterol high, but BP is good —> risk stays low

when women age, risk becomes similar to men

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__ consists of an atheroma plaque and thrombosis. It is involved in most cases of infarction.

Atherosclerosis

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Plaque rupture and hemorrhage into vessel wall precipitates many cases of __, even with coronary artery lumen __ of less than 70%.

infarction; narrowing

meaning can occur even if coronary artery is not significantly narrowed by the build-up plaque (which causes stiffness and narrowing of the vessel)

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__ is a significant cause of ischemia characterized by normal coronary arteries. Usually it doesn’t lead to infarction unless:

spasm; significant atherosclerotic lesion

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What is an example of spasm?

prinzmetal’s angina

  • spasms in (normal) coronary arteries that temporarily restrict blood flow to heart muscle —> reduced oxygen —> pain/angina

39
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__ caused by leutic, collagen, or immune-mediated diseases can lead to cardiac ischemia.

arteritis

40
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__ to coronary arteries can cause cardiac ischemia.

emboli

41
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Infective endocarditis can cause __

emboli to coronary arteries

42
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What occurs when atheroma is initiated?

  1. extracellular lipid accumulation and oxidation: usually occurs when diet is high in cholesterol or saturated fat

  2. leukocyte recruitment via expression of adhesion molecules

  3. foam cell formation: via endothelial and smooth muscle cell chemokine release —> recruit monocytes that differentiate into foam cells

<ol><li><p>extracellular lipid accumulation and oxidation: usually occurs when diet is high in cholesterol or saturated fat</p></li><li><p>leukocyte recruitment via expression of adhesion molecules</p></li><li><p>foam cell formation: via endothelial and smooth muscle cell chemokine release —&gt; recruit monocytes that differentiate into foam cells </p></li></ol><p></p>
43
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During innate and adaptive inflammation in atherogenesis, there is release of __ by foam cells and __ activation.

proinflammatory cytokines; T cell

proinflammatory cytokine release is not Ag (antigen) dependent, but T cell activation needs Ags as infectious agents

44
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How do smooth muscle cells respond during atheroma evolution?

  • migrate to intima layer in response to signals from inflammatory cells and growth factors —> contribute to plaque formation

  • proliferate in the intima & form ECM —> fibrous cap that stabilizes the plaque

  • can undergo apoptosis/cell death —> increases risk of plaque rupture and triggers thrombosis

<ul><li><p>migrate to intima layer in response to signals from inflammatory cells and growth factors —&gt; contribute to plaque formation</p></li><li><p>proliferate in the intima &amp; form ECM  —&gt; fibrous cap that stabilizes the plaque </p></li><li><p>can undergo apoptosis/cell death —&gt; increases risk of plaque rupture and triggers thrombosis </p></li></ul><p></p>
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In a developing atheroma, there is deposition of __ in the arterial extracellular matrix, which contributes to the outward growth of the __.

fibrillar collagen; intima

**this makes atheroma irreversible in size

46
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During atheroma evolution, plaque __ contribute to plaque __.

neovessels; growth

bc more fibrillar collagen deposition means needs more blood supply

  • demonstrates that this is a continuously growing living tissue

47
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Atheroma can become __ to become a fixed, dense plaque on the blood vessel.

mineralized

48
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In arterial stenosis, gradual occlusion and flow limitation occurs, characterizing __ ischemic disease or __.

chronic; angina

can be stable bc occurs very gradually, severity increases as plaque formation increases

49
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A disruption of the plaque or rupture and thrombosis characterizes an __ ischemic disease or __.

acute; acute coronary syndrome (MI/heart attack)

50
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What types of chest pain are consistent with chronic or acute ischemia?

pressure, squeezing, burning (elephant sitting on chest)

less common = sharp and stabbing

51
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Label what type of angina/ischemia might be indicated for the following presentations of chest pain:

  • chest pain present with exercise, emotional stress, large meals relieved with rest

  • chest pain prolonged at rest

  • chest pain frequent at early AM

  • new and acute chest pain (no chest pain before)

  • stable angina

  • unstable angina

  • atypical/prinzmetal’s angina

  • myocardial infarction/MI/heart attack

52
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Pain radiating to left shoulder, jaw, and left arm are consistent for

ischemia

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Chest pain is presented for the following durations. Label each as stable angina, unstable angina, or MI.

  • brief (2-10 min)

  • long pain but <20 min

  • prolonged pain of 30+ min

  • stable angina

  • unstable angina

  • MI

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What are some symptoms associated with acute ischemia? (4)

  • nausea

  • vomiting

  • cold sweat

  • SOB

55
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Coronary vasodilators relieve __.

angina

56
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In __ ischemia, no symptoms are present. This occurs commonly and mortality is as high as __.

silent; when patients present with pain

57
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How does the heart sound in ischemic patients?

usually very distant, gallop rhythms, occasional murmurs

58
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How do the lungs present in ischemic disease?

may be signs of rales/congestive heart failure (congestion in lungs)

59
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How does the patient appear when they have ischemic disease?

pale and in distress

60
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Taking patient’s __ is the most important element of diagnostic work up of acute vs chronic ischemia.

history

61
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When diagnosing IHD with an ECG, it must be taken both __ and __.

at rest; during exercise

62
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How are early/late (serious) ischemias reflected in an ECG reading?

  • evidence of myocardial/early ischemia —> ST and T wave abnormalities

  • evidence of loss of electrically functional cardiac tissue = serious ischemia —> Q wave abnormality

63
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What are limitations of using ECG to diagnose IHD?

  • when combined with exercise for ischemia work up, sensitivity (identifies disease correctly) of ECG is only about 65% while specificity (identifies who does not have correctly) about 90% → better for ruling out ischemia

  • when diagnosing an infarction, changes in infarction may take days to develop following the event

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<p>How do ECG readings change with acute MI evolution? </p>

How do ECG readings change with acute MI evolution?

A&B) show normal QRS

  1. T wave becomes broader and peaks (C)

  2. ST elevation (D)

  3. waves become bigger, ST elevation is maximal, and eventually T wave inversion begins (E&F)

  4. T waves evolve as ST returns to baseline (F)

  5. becomes normal, except Q wave dips a lot —> persistance of Q wave abnormality (G)

<p>A&amp;B) show normal QRS </p><ol><li><p>T wave becomes broader and peaks (C)</p></li><li><p>ST elevation (D)</p></li><li><p>waves become bigger, ST elevation is maximal, and eventually T wave inversion begins (E&amp;F)</p></li><li><p>T waves evolve as ST returns to baseline (F)</p></li><li><p>becomes normal, except Q wave dips a lot —&gt; persistance of Q wave abnormality (G) </p></li></ol><p></p>
65
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What markers/enzymes in plasma indicate ischemia?

  • troponin I (TpI) and troponin T (TnT)

  • creatine kinase (CK) MB isoenzyme

  • lactate dehydrogenase (LDH)

these enzymes are released from damaged cells when infarction occurs

  • troponin & CK are present in a lot of cells: have higher concentration at onset

  • LDH increases slowly after onset and then decreases

<ul><li><p>troponin I (TpI) and troponin T (TnT)</p></li><li><p>creatine kinase (CK) MB isoenzyme</p></li><li><p>lactate dehydrogenase (LDH)</p></li></ul><p></p><p>these enzymes are released from damaged cells when infarction occurs</p><ul><li><p>troponin &amp; CK are present in a lot of cells: have higher concentration at onset</p></li><li><p>LDH increases slowly after onset and then decreases</p></li></ul><p></p>
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How does nuclear cardiology diagnose ischemia?

myocardial perfusion diminishes with ischemia

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How do echocardiograms diagnose ischemia?

abnormal wall motion from ischemia or infarction

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How do coronary angiographies diagnose ischemia?

demonstrates vessel obstruction

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What is the most commonly used nuclear cardiology test?

SPECT scan

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How does a SPECT Scan work?

radioactive tracers/radioisotopes injected via IV and images are obtained with heart at rest or after exercise. because radioisotope concentration in myocardium depends on perfusion rate, the test shows ischemia

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What 2 radioisotopes are used in SPECT scans? What are the differences between them? How do they help with diagnosis?

  • technetium-99m: emits high photon energy and has short half life

  • thallium-201: emits lower photon energy and has longer half life

can provide more detailed images to show severity of ischemia

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What three views can be viewed in a SPECT scan? What do the colors mean?

  • short axis: anterior, inferior, lateral, septal walls

  • vertical long-axis: anterior and inferior walls and apex

  • horizontal long axis: septum, apex, and lateral walls

colors: yellow = more perfused, blue/purple = less perfused

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<p>How does this SPECT Scan show abnormalities? </p>

How does this SPECT Scan show abnormalities?

theres areas of less perfusion, seen by cooler colors, that are in the middle of continuous yellow/more perfused areas

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How does a PET scan work?

isotope tracers are tagged to a glucose analog with a positron-emitting Fluorine-18 molecule. glucose is taken up for metabolic function, so can track metabolic function and tissue viability.

75
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How do SPECT and PET scans compare?

SPECT: shows reduced perfusion areas and highly perfused areas

PET: shows quantative measurement of myocardial perfusion and metabolism (bc tracks through glucose = which is taken up for metabolic fxn)

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<p>What does this PET scan show? </p>

What does this PET scan show?

5 years later, decrease of color bc of less metabolic activity, especially at apical area and inferior segment of myocardium

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How does coronary angiography work?

  • maps blood vessels in coronary system

  • receives dye that goes through systemic vessel —> shows interruptions

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Ambulatory EKG / Holter can be useful for screening __ ischemia.

silent ischemia

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What diagnostic tests are useful to evaluate risk of ischemia?

measurement of lipids and CRP (c-reactive protein)

80
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What are some preventive approaches to IHD? (6)

  • control BP

  • stop smoking

  • dietary changes

  • exercise

  • aspirin —> prevents clotting

  • lipid lowering agents

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What would medications prescribed for IHD target?

  • decrease oxygen demand of myocardium or workforce of myocardium

  • increase oxygen delivery to heart muscle or increase blood flow to heart = vasodilators

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If a patient has already had a thrombotic event already, what can be done immediately?

chew on aspirin to reduce progression to heart attack and symptoms

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What are 4 invasive procedures that can treat IHD?

  • coronary angioplasty- percutaneous transluminal coronary angioplasty (PTCA): uses balloon catheter & intravascular stents

  • coronary artery bypass graft surgery (CABG): can be done off pump

  • laser angioplasty: for definitive large clots that are already identified

  • mechanical atherectomy: device that scrapes areas with plaque

done after initial preventative measures and medications fail to reduce symptoms

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How does an angioplasty with stent work?

inserts catheter with balloon into heart to access coronary arteries. balloon dilates and crushes cholesterol plaque against artery wall. once catheter and balloon are removed, stent remains in place to prevent reobstruction

85
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Angiography and angioplasty are usually done __

at the same time

angiography = imaging procedure that uses dye to visualize inside blood vessels

  • during angioplasty, when inserting catheter, they also insert dye to map and visualize blockages in vessels

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How does CABG (coronary artery bypass graft surgery) work?

establish new pathway to avoid blocked area = bypass

  • heart can’t be beating during this surgery, so use heart-lung machine that takes blood, filters, and repumps back into circulation

  • shocks heart to start beating again

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If a patient presents with a high risk of IHD (unstable coronary syndromes, unstable angina, or recent MI) in a dental setting, how should you proceed?

  • avoid any elective care in the 1st six months after an MI

  • emergency care can be done to target management of pain and infection

    • support patient with vasodilators avail, need IV line, EKG, and pulse oxymeter connected

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If a patient has an intermediate risk (mild angina, previous MI >6 mo ago) in a dental setting, how should you proceed?

reduce stress, pre-treatment vital signs, sedation maybe, limit epi, no epi cords

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__ is not recommended for patients with a history of previous bypass graft surgery, with or without intravascular stents performed > 6 mo ago

antibiotic prophylaxis

  • they may be considered immediately after surgery and up to first 6 months

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If a patient with IHD is in the dental setting, what medications should you be cautious of?

anticoagulants

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When does ischemia occur?

when myocardial oxygen demand is not met adequately

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__ plays a large role in IHD.

atherosclerosis

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Ischemia can lead to: (3)

  • contractile dysfunction

  • arrhythmia

  • infarction

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What are some common diagnostic tests for IHD? (3)

  • cardiac perfusion tests

  • electrical conduction

  • cardiac enzymes

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What common modalities are available for treatment of IHD? (3)

  • drugs that improve coronary circulation

  • angioplasty

  • bypass graft surgery