Pathology of Ischemic CV Disease Flashcards
Heart disease is secondary to many things. Name 4 of the more common ones, and two less common.
- valve abnormalities 2. coronary atherosclerosis 3. hypertension 4. congenital anomalies 1. Primary Idiopathic Cardiomyopathy 2. Specific heart muscle disease (myocarditis, sarcoidosis, amyloidosis, hemochromatosis, etc.)
What is Ischemic Heart Disease (IHD)?
IHD is a variety of syndromes when myocardial O2 requirement exceeds cardiac blood supply
What is the greatest cause (accounting for >90%) of IHD cases?
Obstructive Coronary Atherosclerosis
Symptomatic IHD (stable angina) is typically associated with increased oxygen demand in the presence of >____% coronary atherosclerotic obstruction.
70%
>____% stenosis can lead to symptoms even at rest (unstable angina)
90%
Myocardial ischemia depends on the extent and severity of the coronary artery stenosis AND the +/- of _________
exacerbating factors
Name 3 exacerbating factors of coronary atherosclerosis.
- Coronary artery vasospasm 2. Platelet aggregation +/- coronary vasospasm 3. Hypotensive episode (e.g. shock, massive hemorrhage in the presence of critically stenosed coronary artery)
What 2 harmful things does coronary artery vasospasm cause?
Directly compromises lumen and increases local mechanical shear forces which may contribute to plaque rupture
What are 6 less frequent causes of myocardial ischemia (IHD)?
- increased myocardial O2 demand (increased HR, HTN) 2. Decreased blood volume (hypotension) 3. Decreased oxygenation (pneumonia) 4. Decreased O2 carrying capacity (anemia) 5. Arteritis (inflammation narrows lumen) 6. Cocaine Abuse (mechanism is vasospasm)
What is Chronic Ischemic Heart Disease?
Chronic Ischemic Heart Disease is when there is progressive cardiac decompensation following an acute infarct or multiple small ischemic events with development of contractile impairment due to replacement of myocardium by fibrous tissue (non contractile)
What is the difference between stable and vulnerable plaques?
Stable plaques have densely collagenized thickened fibrous caps with minimal inflammation and small atheromatous/lipid cores. Vulnerable plaques are non-obstructive plaques prone to rupture or superimposed acute thrombus. These are thin fibrous caps which are unable to withstand circumferential stress. Large lipid core composed of extracellular lipid released by macrophage cell death.
What are 4 things that happen with vulnerable plaque?
- Increased plaque inflammation (macrophages/T cells degrade ECM by phagocytosis or proteolytic enzyme secretion and weaken the thin fibrous plaque) 2. Vascular remodeling which is associated with plaque inflammation 3. Vasa vasorum neovascularization of the plaque starts to provide oxygen and remove lipid but fails (lacks supporting cells) red blood cell extravasation, inflammation, and hemorrhage which can lead to luminal narrowing. 4. Intra plaque hemorrhage associated with extravasation of red blood cells with their breakdown and further tissue damage.
What are erosion type plaques?
These are heterogenous but in general have little inflammation, often no calcification and an eroded/missing endothelial layer at the plaque-thrombus interface.
What kind of patients are erosion type plaques more common in?
Females
What is the most common cause of myocardial infarction?
>90% are due to acute coronary artery thrombus superimposed on severe atherosclerosis with plaque rupture.
Where do myocardial infarcts start?
Typically, in the subendocardial region. This is because this is the most poorly perfused and hence more vulnerable region
If myocardial infarcts start in the subendocardial region, where do they progress to?
They progress outwards towards the epicardial region over several hours. Interventions may limit the progression.
What has a more detrimental effect? Myocardial ischemia due to hypoxia AND low blood flow or just hypoxia alone?
Hypoxia and low blood flow together have a more detrimental effect due to the added detrimental metabolic problems.
What are the 4 determinants of the extent of myocardial infarction?
- Site of occlusion (proximal or distal) 2. Duration of ischemia 3. Extent of any collateral circulation (there is more collateral circulation in the outer myocardium which is another reason that subendocardial area is more susceptible to infarct) 4. Metabolic needs of the myocardium
What is myocardial infarction reperfusion injury?
This is injury that occurs to myocytes following restoration of blood flow
What are 5 causes of reperfusion injury?
- Mitochondrial dysfunction 2. Influx of calcium causing myofibril hypercontracture with cytoskeletal damage and cell death 3. Free radicals damage membrane proteins and phospholipids 4. Leukocyte aggregation 5. Platelet and complement activation
Which part(s) of the heart are the most common sites for myocardial infarction?
LV and septum. Only 1-3% involve RV alone. This is because LV has a larger mass, higher workload, and oxygen demand.
For myocardial infarcts, what is the time frame in which ultrastructural and biochemical changes are reversible?
0-30 minutes
For myocardial infarcts, what is the time frame in which ultrastructural and biochemical changes begin to be irreversible?
1-2 hours
What are 3 examples of reversible ultrastructural/biochemical changes?
- mitochondrial swelling 2. sarcoplasmic edema 3. loss of glycogen
What are 3 examples of irreversible ultrastructural/biochemical changes?
- sarcolemmal disruption 2. release of intracellular proteins 3. ion gradient disruption
When looking at macroscopic and light microscopy, what findings do you expect to see after 4-12 hours of infarction?
Wavy fibers (non contractile ischemic fibers stretched with each systole)
When looking at macroscopic and light microscopy, what findings do you expect to see after 18-24 hours of infarction?
Coagulation necrosis, neutrophils, pallor, and contraction bands at edge of infarct
When looking at macroscopic and light microscopy, what findings do you expect to see after 24-72 hours of infarction?
Maximum coagulation necrosis and neutrophils
When looking at macroscopic and light microscopy, what findings do you expect to see after 4-7 days of infarction?
Macrophages with disintegration of the myocytes (maximal softening). Pallor with hyperemic border
When looking at macroscopic and light microscopy, what findings do you expect to see after 10 days of infarction?
Granulation tissue. Yellow, soft with dark border.
When looking at macroscopic and light microscopy, what findings do you expect to see after 4-8 weeks of infarction?
Fibrosis. Firm and gray.
What is this picture of?
Fibrosis
What is this a picture of?
Granulation tissue and a lot of vascularity trying to rebuild
Of all who have MIs, how many have sudden cardiac death and don’t even make it to the hospital?
25%
Out of all the MI cases that are treated at the hospital, how many (percentage) will have complications? And what are 4 of the complications?
80-90%
- Arrhythmias
- LV failure with pulmonary edema
- Cardiogenic shock (if >40% LV infarct)
- Pericarditis (chest pain, friction rub)
What is this a picture of? (hint: lung)
This is a normal lung with clear alveolar spaces
What is this a picture of? (hint: lung)
This is a patient with severe left heart failure with pulmonary edema.
What is papillary muscle dysfunction?
Papillary muscle dysfunction is infarction or rupture of the papillary muscle which results in valve incompetence. This causes the valves to not close properly and results in regurgitation and heart murmur.
How can rupture of the LV free wall or septum occur after MI? What is the time frame after an MI that this can occur?
LV free wall or septum rupture can occur within the first 3 weeks, usually within 2-10 days post infarction. This happens around the 4-7 days period where macrophages disintegrate the myocytes (maximal softening)
Thrombus is a dangerous complication of MI. Explain.
Thrombus can form when there are transmural infarcts. The thrombus forms right against the area that is infarcted. During contractions, the area that had infarct won’t be contracting which allows thrombus to form. Parts of the thrombus can break off and cause stroke, kidney infarct, etc (thromboembolus)
For thrombus complication in MI, is it acute or can it happen later on too?
It can be acute or also happen later on.