Ischemic Heart Disease Flashcards
What is the cause of most ischemic heart disease?
Coronary atherosclerotic lesions
What are the clinical syndromes associated with ischemic heart disease?
Myocardial infarction
Angina
Worsening ischemia followed by cardiac failure
Sudden cardiac death
At what occlusion percentage are symptoms seen?
At 70% symptomatic ischemia is preceded by exercise
At 90% there are symptoms at rest
What is acute coronary syndrome?
When a stable plaque suddenly becomes an unstable atherosclerotic lesion and a superimposed thrombus occludes the affected artery
What is acute coronary syndrome associated with?
Intra-lesional inflammation
Where are most clinically significant plaques located?
In the first few cm of the left anterior descending artery, the left circumflex artery, and the entire right coronary artery. Also, secondary major epicardial branches
Describe the pathogenesis of acute coronary syndrome
Sudden change in plaque
Platelets adhere to the plaque and release granules
Thrombi forms
Vasospasm
Tissue factors activate the coagulation pathway
Occlusion
What can cause myocardial infarction when there is no coronary atherosclerosis?
Vasospasm due to platelet aggregation or cocaine abuse
Where can emboli form in these cases and why?
left atrium due to atrial fibrillation, prosthetic material, mural thrombi, or vegetation from infective endocarditis
right atrium, paradoxical emboli
What are 4 possible causes of myocardial ischemia without atherosclerosis or emboli?
Disorders of blood vessels such as vasculitis
Hematologic disorders like sickle cell or amyloid deposition
Low blood pressure from shock
Improper myocardial protection during surgery
Describe the progression of coronary lesions
Fixed coronary lesion or atherosclerosis
- Plaque disruption and it is then patched by platelets causing severe obstruction
- Either have mural thrombus with variable levels of obstruction or full obstruction leads to death
Where does myocardial necrosis begin?
Subendocardial zone
What happens to the heart within the first few minutes after cessation of aerobic metabolism?
Relaxation of muscles, glycogen depletion, cell and mitochondrial swelling
Is the damage within the first few minutes reversible?
Yes
When does irreversible damage of cardiac myocytes take place?
After 20-30 minutes,
