IHD Patho Flashcards
1
Q
Myocardial Ischemia
A
Lack of oxygen and reduced blood flow to the myocardium resulting in an imbalance between myocardial oxygen supply and demand
2
Q
Myocardial Infarction
A
Necrosis (death) of heart muscle caused by an imbalance between oxygen supply and demand
3
Q
Angina Pectoris
A
“Chest pain”; pain or discomfort in the chest or adjacent areas which is due to myocardial ischemia
4
Q
Silent Ischemia
A
Painless episodes of myocardial ischemia (75% of all ischemia)
5
Q
Silent Infarction
A
Infarction occurring without chest pain or other common symptoms of ischemia; about 20% of all first infarcts
6
Q
Acute Coronary Syndrome
A
Unstable angina or acute myocardial infarction
7
Q
Myocardial Oxygen Demand
A
- Heart Rate
- Wall Tension
- Contactility
8
Q
Wall Tension
A
- Related to ventricular volume and wall pressure
- Preload v.s. Afterload
9
Q
Myocardial Oxygen Supply
A
- Coronary Blood Flow
- Collaterals
- Autoregulation
- Other factors that regulate coronary blood flow
10
Q
Coronary Blood Flor
A
- Increased oxygen demand must be met by an increase in coronary blood flow
- Coronary blood flow can normally increase 5x resting value
- Coronary blood flow occurs primarily during diastole
- May be altered by fixed obstruction or vasospasm
11
Q
Collaterals
A
- Provide blood flow when major vessels are obstructed
- Development enhanced by gradual coronary occlusion, exercise, severe anemia
- May prevent a myocardial infarction in the presence of total occlusion
12
Q
Autoregulation
A
-As larger coronary arteries become occluded or stenotic, smaller vessels dilate to maintain coronary blood flow
13
Q
Other Factors
A
- Neural (symp v.s. parasymp.)
- Endothelium - EDRF, endothelin, prostaglandins, others
- Metabolic - oxygen, carbon dioxide, adenosine
14
Q
Oxygen Extraction
A
- At rest, 65-75% of oxygen passing through myocardium is extracted
- With increased oxygen demand, oxygen extraction can approach 80%
15
Q
Blood Oxygen Content
A
- Hemoglobin/hematocrit
- Arterial blood gases
16
Q
Types of Ischemic Heart Disease
A
- Chronic Stable Angina
- Unstable Angina
- Vasospastic Angina (Prinzmetal’s Variant)
- Myocardial Infarction (MI)
17
Q
Chronic Stable Angina
A
- Associated with a certain level of physical activity or emotional stress
- Relieved by rest or nitroglycerin
18
Q
Unstable Angina
A
- Angina of new onset, usually within one month and brought on by minial exertion
- Development of crescendo (more severe) pain superimposed on preexisting exertion-related angina
- Any change in angina frequency, intensity, or duration
- Pain at rest
- No elevated cardiac enzymes or ST-segment elevation
19
Q
Vasospastic Angina
A
- Occurs in patients with or without coronary heart disease and is due to a spasm of a coronary artery that decreases myocardial blood flow
- More likely to experience pain at rest and in the early morning hours
- Pain not usually brought on by exertion or emotional stress or relieved by rest
- Occurs more often in smokers, young patients, with illicit drug use, and with alcohol withdrawal
20
Q
Myocardial Infarction
A
- Most common due to artherosclerotic thrombosis
- Coronary spasm and coronary embolus may also cause infarction
- ST-segment and Non-ST segment elevation MI
21
Q
STEMI
A
- ST-segment elevation MI
- MI characterized by ST-segment elevation on the ECG in at least 2 contiguous leads of >= 2 mm in men or >= 1.5 mm in women in leads V2-V3 and/or ?= 1 mm in other contiguous chest leads or the limb leads
- More extensive infarct
- Higher hospital mortality rate
- Elevated cardiac enzymes
22
Q
NSTEMI
A
- Non-ST-segment elevation MI
- Damage to myocardium is not as extensive
- Increased likelihood of developing post-infarction angina and early reinfarction
- Elevated cardiac enzymes
23
Q
Type I MI
A
- Spontaneous MI
- Due to atherosclerotic plaque rupture and thrombus formation
- Vast majority of MI
24
Q
Type II MI
A
- Due to ischemic imbalance
- NOT due to plaque rupture, but end result is in inadequate oxygenation of myocardial tissue
- EX: coronary vasospasm, hypotension, anemia, etc.
25
Type 3 MI
- Fatal MI in the setting of no cardiac biomarkers
- REsults in death and suspected based on symptoms and ECG findings
- No cardiac biomarkers obtained
26
Type 4a MI
- Due to PCI
- Confirmed by troponin elevations and one or more of the following:
1. Symptoms of ischemia
2. ECG changes
3. Angiographic evidence of coronary artery obstruction
4. Imaging evidence of myocardial damage
27
Type 4b MI
- Due to stent thrombosis
| - Confirmed by an increase in cardiac biomarkers
28
Type 5 MI
- Due to CABG
- Confirmed by the increase in cardiac biomarkers and one or more of the following:
1. New Q waves or left bundle branch block on ECG
2. Angiographic evidence of new coronary artery obstruction
3. Imaging evidence of myocardial damage
29
Patho of Atherosclerosis
1. Phase 1: small plaque that is present in most people < 30 y.o., usually progresses slowly
2. Phase 2: Plaque, not necessarily stenotic, with high lipid content and is prone to rupture
3. Phase 3: Plaque rupture with mural thombosis formation, leads to an increase in artery stenosis and possibly angina
4. Phase 4: Plaque rupture leading to an acute coronary occlusion, leads to unstable angina, AMI, or ischemic sudden death
5. Phase 5: Severely stenotic or occlusion plaques organized by connective tissue, may become complicated by a thrombus and/or myoproliferative response leading to an acute silent occlusive process
30
Plaque Rupture
- Most complications of atherosclerosis are due to plaque rupture
- Rupture tends to occur at junctions, branches, or bends in the vessel
31
Clot Formation
- Platelet deposition: first step in hemostasis and thrombus formation, increases with an increase in shear force
- Platelet activation causes conformational change in GP IIb/IIIa receptor, allowing it to bind to fibrinogen
- Fibrinogen cross-links develop and form bridges to otehr platelets, facilitating aggregation and ultimately platelet plug
- Platelets generate thrombin and convert fibrinogen to fibrin which converts white thrombus to a stable red-thrombus
- Plaque composition may be MOST important determinant for plaque rupture/fissure
32
Glycoproteins
- Different GP adhere to various adhesive proteins found in subendothelial matrix which are exposed by vessel damage
- GP Ib: binds von Willebrand factor
- GP Ia/IIA: binds collagen
- GP Ic/IIa: binds fibronectin
- GP IIb/IIa: plays a secondary role in platelet adhesion
33
History/Risk Factor Assessment
- Part of Diagnosis of IHD
- No physical findings are specific for angina
- Characteristics of pain
- Laboratory assessment is not helpful except for cardiac enzymes
- Patient's cardiac risk factors
- Pain with unstable angina typically lasts 10-20 minutes
- Pain with non-ST-elevation MI typically lasts up to an hour
- Pain with an ST-elevation MI typically lasts > 1 hour
34
ECG
- Used in diagnosis of IHD
- Resting ECG is normal in about 30-50% of patients with angina
- ST-T wave changes
- Q waves with infarction
- Use of ambulatory monitoring to detect silent ischemia
35
Exercise Tolerance Testing (ETT)
- Used in diagnosis of IHD
- Useful for assessing the severity and prognosis of CAD
- Positive test indicated by angina, ECG changes, or dysrhythmias
- Abnormal BP or HR response may signal CAD
36
Radionuclide Imaging
- Used in diagnosis of IHD
- Patient is stressed with either exercise or pharmacologically and then myocardial imaging performed using either sestamibi or thallium
- Defect in myocardial uptake of sestamibi or thallium indicates ischemia or infarction
- More expensive than ETT
37
Radionuclide Imaging Useful for patients....
- Unable to exercise completely
- Asymptomatic with abnormal results on ETT
- Men with typical angina who have "negative" results on ETT
- Women with typical angina who have equivocal ETT results
- Patients with known CAD to determine myocardial viability
38
Coronary Angiography
- Used in diagnosis of IHD and definitive diagnosis of CAD
- Allows determination of location and extent of atherosclerosis
- Used when bypass surgery or angioplasty are being contemplated for therapy
- Does not give functional information
39
Cardiac Enzymes
- Used in diagnosis of IHD
- Creatine kinase (CK or CPK)
- Isoenzymes: MM (muscle), BB (brain), MB (myocardium)
- Troponins I and T
