Lect 5- Ischemic Heart Disease

Question 1

Ischemic heart disease definition

Answer 1

inadequate supply of blood and oxygen to a portion of the myocardium
occurs when there is an imbalance b/w oxygen supply and demand

Question 2

what is the most common cause of myocardial ischemia?

Answer 2

atherosclerotic disease

atherosclerotic lesions reduce blood flow to the myocardium

Question 3

what are powerful risk factors for IHD?

Answer 3

obesity, insulin resistance, and Type 2 DM

overlap b/w risk factors

Question 4

major pathophysiological mechanism behind IHD

Answer 4

imbalance b/w myocardial oxygen demand (MVO2) and delivery

Question 5

hypoxia vs ischemia

Answer 5

• Ischemia is a broader term vs hypoxia is a more narrow term
○ Ischemia is lack of oxygen as well as nutrients whereas hypoxia is just lack of oxygen
hypoxia exacerbates effects of atherosclerosisPatho of IHD can be affected by factors that affect these three things (MVO2, oxygen-carrying capacity of the blood, and coronary blood flow)

Question 6

the oxygen-carrying capacity of the blood is determined by:

Answer 6

the inspired level of O2, pulmonary function, Hb conc and function

Question 7

coronary blood flow

Answer 7

Major factor which regulates blood flow is resistance of all of these coronary arteries
1.) Large epicardial arteries (R1) 2.) prearteriolar vessels (R2) and 3.) arteriolar and intramyocardial capillary vessels (R3)
In the absence of significant flow (atherosclerotic obstructions), the major determinant of coronary resistance is R2 and R3

Question 8

Coronary blood flow is controlled by what?

Answer 8

Metabolic regulation= exercise, emotional stress, etc

Autoregulation= blood flow is kept at certain range independent to changes in BP (protective mechanism)

Question 9

Rupture of a plaque

Answer 9

fibrous cap is broken → tissue factor that is separated from blood is released → initiates coagulation/ thrombosis → can cause narrowing of blood vessel or complete occlusion or can resolve w/o any clinical sx
○ If you have complete occlusion → MI

Question 10

other causes of IHD

Answer 10

spasm, thrombi, emboli, BP decrease (from blood loss), Aortitis, congenital abnormalities, left ventricular hypertrophy (since O2 demand is higher), severe anemia, abnormal constriction or failure of normal dilation of resistance vessels

Question 11

where is there coronary atherosclerosis?

Answer 11

sites of increased turbulence in coronary flow and branch points in the epicardial arteries

Question 12

what are the risk factors for coronary atherosclerosis?

Answer 12

exactly the same as for atherosclerosis

high LDL, low HDL, smoking, HTN, DM

Question 13

severity of symptoms in IHD

Answer 13

depends on degree and location of stenosis and how fast it develops (chronic process and it takes years to get to the stage where sx are present)

Question 14

50% stenosis in IHD

Answer 14

Usually pts do not have sx if they do regular activities but they might have sx if they do cardio/ exercise

Question 15

80% stenosis in IHD

Answer 15

blood flow AT REST may be reduced

Question 16

which arteries are particularly hazardous to develop stenosis?

Answer 16

left main coronary artery or the proximal left anterior descending

Question 17

formation of collateral vessels

Answer 17

GOOD!
Collateral circulation affects the way the disease is produced
Formed when gradually developing stenosis

Question 18

effects of ischemia

Answer 18

inadequate perfusion; decreased myocardial O2 tension; mechanical, biochemical and electrical disturbances

Question 19

what are the mechanical effects of ischemia?

Answer 19

regional disturbances of ventricular contractility; segmental hypokinesia; segmental akinesia; segmental dyskinesia
all eventually lead to reduced myocardial pump function

Question 20

effects of acute ischemia

Answer 20

transient left ventricle failure and mitral regurgitation (if the papillary muscle apparatus is involved; papillary muscles control the valves in the heart)
Mitral regurgitation= reversed blood flow; blood goes back from left ventricle to left atrium

Question 21

what effect of transient ischemia would we see in clinic?

Answer 21

angina pectoris= chest pain

Question 22

what effect of prolonged ischemia would we see in clinic?

Answer 22

acute MI
• Prolonged ischemia= severe narrowing/ blockage
• Myocardial infarction= tissue necrosis
○ Irreversible tissue damage/ cells are dying

Question 23

ECG in IHD

Answer 23

Can determine:
if it is reversible vs irreversible process (need to know it before you treat pts)
the duration
the extent of damage
localization
presence of other underlying abnormalities

Question 24

what will you find on an ECG of a pt with IHD?

Answer 24

• Ischemia= problems with ventricular repolarization
• ST depression= indicates ischemia (partial thickness)
• Dramatic ST elevation= entire thickness

Question 25

effects of ischemia

Answer 25

electrical instability, which may lead to ventricular arrhythmia's or ventricular fibrillation

Question 26

diagnosis of IHD

Answer 26

many may be asymptomatic exercise-induced ECG changes angiography 25% of pts who survive acute MI may not come to medical attention

Question 27

symptoms of IHD

Answer 27

• Chronic disease and most of the time asymptomatic (takes many years to develop bad symptoms) • Complain of pressure, pain, and other forms of chest discomfort ○ Pts not always complaining of pain • Sometimes angina pectoris is a condition which will eventually lead to MI ○ However, in some pts, the first event to bring them to the hospital is acute MI • Disease can have a stable course= pt has the same complaints over a long period of time • Progressive= sx are more often or occurring after less and less exercise • Death= w/o any sx that can warn the pt that something has gone wrong chest discomfort due to: angina pectoris, acute MI

Question 28

classification of IHD

Answer 28

1. ) chronic coronary artery disease (CAD)= stable angina 2. ) acute coronary syndromes (ACSs)= progressive; acute MI, unstable angina, NSTEMI, sudden cardiac death, Prinzmetal's Variant Angina (special type)

Question 29

reading an ECG

Answer 29

• Need to understand that P-wave reflects the initial stimulation and conduction of impulses from atria to ventricles • QRS= reflects depolarization of ventricles • Everything after QRS is repolarization ○ ST segment very important for IHD

Question 30

What are the outcomes of a partial occlusion of a blood vessel?

Answer 30

• Partial occlusion= can have 2 outcomes ○ Unstable angina pectoris= ischemia but the damage is reversible ○ Acute MI w/o ST elevation= irreversible damage/ necrosis

Question 31

STEMI

Answer 31

assoc w/ complete occlusion

Question 32

NSTEMI

Answer 32

assoc w/ partial occlusion

Question 33

stable angina pectoris age

Answer 33

male over 50 and women over 60 (since until 50 women are protected by estrogen)

Question 34

clinical manifestations of stable angina pectoris

Answer 34

chest discomfort (not always pain), crescendo-descresendo, radiates to shoulders, sx relieved by rest or sublingual nitroglycerin, dyspnea, nausea, fatigue, faintness

Question 35

how can you tell if the pt is progressing to unstable angina?

Answer 35

ALWAYS ASK | angina occurring with less exertion than in the past, occurring at rest, or awakening the pt from sleep

Question 36

physical examination for IHS

Answer 36

search for evidence of atherosclerotic disease at other sites such as carotid arterial bruits (if you put stethoscope on neck, you can hear noise due to narrowing)

Question 37

unstable angina/ NSTEMI definitions

Answer 37

angina pectoris or equivalent ischemic discomfort w/ at least 1 of 3 features: 1. occurs at rest, usually for >10 min 2. severe and of new onset (w/in prior 4-6 weeks) 3. occurs with a crescendo pattern NSTEMI= UA + myocardial necrosis (biomarkers)

Question 38

clinical manifestations of UA/ NSTEMI

Answer 38

``` chest pain (usually severe enough to be described as frank pain), dyspnea and epigastric discomfort large ischemia or NSTEMI= diaphoresis, pale, cool skin, tachycardia, basilar rales ```

Question 39

cardiac markers for UA/NSTEMI

Answer 39

CK-MB and troponin When cells are dying, these cells are released to the circulation Key to distinguish b/w reversible injury (unstable angina) and MI direct relationship b/w the degree of troponin elevation and mortality

Question 40

Prinzmetal's Variant Angina

Answer 40

syndrome of severe ischemic pain that occurs at rest but not usually w/ exertion and is assoc with transient ST-segment elevation due to focal spasm of an epicardial coronary artery pathogenesis is unclear

Question 41

STEMI

Answer 41

myocardial cell death due to prolonged and severe ischemia (b/w 2-4 hours of ischemia) ST-elevation Assoc with complete occlusion by thrombus

Question 42

coronary plaques prone to disruption

Answer 42

Thin fibrous cap | Thick fibrous cap and thin lipid core= safe; not likely to rupture

Question 43

coronary emboli vs coronary thrombus

Answer 43

Coronary emboli= thrombotic material is formed somewhere else in the body and travels to the coronary arteries to occlude them thrombi are formed at the site of vascular injury in the coronary artery

Question 44

risk factors for STEMI

Answer 44

multiple: UA (can progress to clinically obvious MI), hypercoagulability, collagen vascular diseases, cocaine abuse, intracardiac thrombi, coronary emboli

Question 45

clinical manifestations of STEMI

Answer 45

pain is deep and visceral; (heavy squeezing, and crushing), occurs at rest (more severe and last longer), weakness, sweating, nausea, vomiting, anxiety

Question 46

physical findings of STEMI

Answer 46

substernal chest pain persisting for >30 min and diaphoresis, tachycardia and/or hypotension (anterior MI), bradycardia and/or hypotension (inferior MI), pericardial friction rub, temp elevation

Question 47

diagnosis of STEMI

Answer 47

ECG, biomarkers, imaging, non-specific indicators of tissue necrosis and inflammation

Question 48

biomarkers for STEMI

Answer 48

cardiac-specific troponin, cardiac-specific troponin-1, CK, CKMB (MB isoenzyme) released when there is tissue damage

Question 49

what chemical is used as a dye in autopsies to see a fresh MI better?

Answer 49

triphenyltetrazolium chloride

Question 50

progression of myocardial necrosis

Answer 50

* Occlusion of coronary artery less than 2 hours= tissue can be helped * Occlusion for more than 2 hours= entire area can be necrotic * Longer occlusion= larger area of tissue damage

Question 51

stages and histology of MI

Answer 51

LOOK AT SLIDE

Question 52

reperfusion

Answer 52

RESCUE!=Critical to restore circulation! | however sometimes there are complications to reperfusion

Question 53

preconditioning

Answer 53

situation in which repetitive ischemia is preparing myocardium to survive long periods of ischemia

Question 54

consequences of myocardial ischemia followed by reperfusion

Answer 54

* If the blood flow is restored w/in 20 min, the entire area will be healthy/ no necrosis * Longer ischemia; reperfusion w/in 2-4 hours= some damaged tissue but some tissue will be healthy after some time * Permanent ischemia/ no restoration of blood flow, entire area will be necrotic

Question 55

complications of myocardial ischemia

Answer 55

acute left ventricular failure, pulmonary edema, shock, arrhythmias, myocardial rupture, hemopericardium (hemorrhage in myocardial cavity), pericarditis (Dressler Syndrome)

Question 56

acute ischemic injury

Answer 56

* Global cerebral ischemia= Usually assoc w/ systemic reasons (cardiac arrest, shock, severe hypotension) * Focal cerebral ischemia= Only the portion of brain is affect

Question 57

global cerebral ischemia

Answer 57

mild cases= transient post-ischemic confusional state | severe cases= persistent vegetative state; "Respirator brain"

Question 58

focal cerebral ischemia

Answer 58

If sustained, leads to infarction * Thrombotic occlusion due to atherosclerosis * Embolism * Vasculitis

Question 59

2 types of brain infarction

Answer 59

1. ) hemorrhagic= with blood | 2. ) non-hemorrhagic (pale, anemic)= due to ischemia