Ischemic Heart Disease Flashcards
What is angia pectoris? Syx?
Pain of myocardial ischemia; Severe crushing/burning sensation in the substernal portion of the chest and may radiate to left arm, jaw, or epigastrium
What is Prinzmetal angia? Cause?
Atypical form of angina that occurs at rest and may be caused by coronary vasospasm
What is unstable angina? Causes?
Variety of chest pain that has a less predictable relationship to exercise than does stable angina and may occur during rest/sleep; Associated with development of nonocclusive thrombi over athersclerotic plaques
When does stable angina generally occur?
During exertion/exercise
What is a myocardial infarction?
Discrete focus of ischemic muscle necrosis in the heart excluding patchy necrosis caused by drugs/toxins/viruses
What is responsible for heart failure in more than 75% of all patients with heart failure?
Coronary artery disease
What underlies most cases of cardiac death occurring during the first hour after the onset of Syx? What is the general physiological progression starting from ischemia leading to death?
Atherosclerosis of coronary vessels; Ischemia -> Ventricular Tachycardia -> Ventricular Fib -> Death
What is lethal arrhythmia likely triggered by?
Acute ischemia without overt myocardial infarction
What are the 4 major risk factors that predispose to coronary artery disease?
- Systemic hypertension
- Cigarette smoking
- Diabetes mellitus
- Elevated blood cholesterol
At what point is maximal blood flow to the myocardium impaired? When is resting blood flow impaired?
75% of cross-sectional area (50% of diameter) is blocked; 90% of lumen occluded
What does coronary thrombosis usually cause?
Acute myocardial infarction
How common are MI caused by thromboemboli? Where do the thromboemboli generally originate?
Rare; Usually heart valvular vegetations caused by infective or nonbacterial endocarditis
By what mechanism is coronary collateral circulation created? Describe the mechanism of infarction at a distance of the anterior infarction.
Develop in response to coronary athersclerosis; Collateral vessels are formed between the right coronary artery and the left anterior descending artery in response to occlusion of the LAD. Acute blockage of the RCA stops bloodflow through the collateral circultion resulting in anterior infarction
How does syphilitic aortitis cause ischemic heart disease?
By obliterating the coronary artery orifice
Describe the physiology in which ischemic heart disease is caused by an intramural coursing of the LAD
The LAD normally runs in the epicardial fat. Occasionally it passes through the myocardium and can be blocked during systole from the muscle
Describe the scenario in which anemia could cause ischemic heart disease
Anemia alone generally does not affect the heart. With concurrent atherosclerosis, there may be limited compensatory increases in coronary blood flow
Describe how hyperthyroid can lead to ischemic cardiac disease
Hyperthyroid leads to increased metabolic rate and tachycardia and results in increased oxygen demand and greater cardiac workload
What is a subendocardial infarct?
An infarction that affects the inner one third to one half of the left ventricle
What is the general cause of subendocardial infarction?
Generally results from hypoperfusion of the heart
What is a transmural infarct?
Infarction involving the full left ventricular wall thickness usually after occlusion of a coronary artery.
Occlusion of what three vessels generally results in transmural infarcts?
RCA, LAD, Left circumflex CA
What is the general progression of a myocardial infarction?
First develops in the subendocardium and progresses as a wavefront of necrosis from subendocardium to subepicardium over the course of several hours
What is the chief determinant of transmural progression of an infarct?
The volume of arterial collateral flow
In chronic cardiac hypoperfusion, what would limit the infarct to the subendocardium?
Collateral bloodflow
What part of the heart experiences infarcts most commonly?
Left Ventricle
How long is the reversible stage of myocardial ischemia?
20-30 minutes
Following infarction, what are the macroscopic changes in the heart at:
- 12 hours
- 24 hours
- 3-5 days
- 2-3 weeks
- Healed
- 12 hours: infarct not identifiable
- 24 hours: tissue is pallid
- 3-5 days: tissue is mottled and sharply outlined
- 2-3 weeks: depressed and soft
- Healed: Gray and firm
What occurs in the mitochondria within the first 24 hours of MI?
Mitochondria become swollen with disorganized cristae
What are “wavy fibers” and when can they be observed?
Noncontractile ischemic myocytes stretched with each systole (seen on uscopic exam of MI heart)
In 2 to 3 days following infarction, what uscopic changes are seen in the heart?
PMNs gain access to the periphery of the infarct
What are the uscopic changes that occur in 5-7 days following infarction?
Dead muscle is phagocytosed by macrophages and fibroblasts begin to proliferate and new collagen is deposited
What are the uscopic changes that occur in 1 to 3 weeks following an MI?
Procession of collagen deposition and decrease in inflammatory processes
What are the processes that occur more than 4 weeks following infarction?
Dense fibrous tissue is present and debris is progressively removed
What would one expect to be able to see on a healed MI?
Collagenous matrix (green) intermingled with viable myocardium
What is the danger of reperfusion injury?
Accelerates the inflammatory process by delivering oxygen (creating free-radical oxygen species) and inflammatory cells to the injury site
What is is this? What is it characteristic of? What is the pathogenesis? What other conidtions can cause it? When is it most prominent?
Contraction band necrosis; Reperfusion infarction; Blood delivers Ca to injured tissue leading to hypercontraction of healthy tissue; Influx of catecholamines or pressors can also cause this condition following infarction; When ischemic myocardium is reperfused
How is acute MI diagnosed?
Confirmed by electrocardiography and appearance of increased levels of cardiac enzymes
What are 8 complications of a myocardial infarction?
- Arrhythmias
- Left Ventricular Failure
- Cardiogenic shock
- Extension of the Infarct
- Rupture of the free wall of the myocardium
- Aneurysms
- Mural Thrombosis/Embolism
- Pericarditis
When does extension of a myocardial infarct generally occur?
in first 1-2 weeks following MI
A heart at autopsy. What is the Dx? What is this a complication of?
Myocardial rupture; Transmural infarction
In a myocardial rupture of the left ventricle, what is the most common cause of death?
Hemopericardium and pericardial tamponade
What type of infarction generally causes an aneurysm? What is the difference betwixt a true and false aneurysm? Which has a wider mouth?
Transmural infarct;
- True - an intact myocardial wall that bulges out
- False - ruptured infarct that is walled off externally by adherent pericardium
True has a wider mouth
What can mural thrombosis/embolism lead to following an infarct?
Systemic embolism (stroke, myocardial/visceral infarcts)
What is postmyocardial infarction syndrome (Dressler Syndrome)?
Auto-abs to heart muscle that causes pericarditis following either MI or cardiac surgery
Name 4 therapeutic interventions that can limit infarction size
- Restoration of arterial blood flow
- Thrombolytic Enzymes
- Percutaneous Coronary Intervention (Dilation of coronary artery by inflation witha balloon catheter)
- Coronary Artery Bypass Grafting
What can repetitive episodes of ischemic injury (without obvious infarction) lead to?
Ischemic cardiomyopathy
