Patho 2 Unit 1
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How does coronary artery disease (CAD; atherosclerosis of the coronary a.) present itself clinically?
- Angina pectoris (chest pain)
- Chronic ischemic heart disease w/ CHF
- Acute myocardial infarction (MI)
- Sudden cardiac death
What is the underlying mechanism of coronary a. disease?
How do atherosclerotic lesions cause acute coronary syndromes?
1) Fissuring of plague w/ clotting
2) Plague ruptures w/ emobolization
3) Results in thromboemboli
What results from an imbalance between myocardial oxygen demand and myocardial bloody supply?
Ischemic heart disease
How does coronary occlusion affect myocardial cells?
- @ 10 sec: become hypoxic from inadequate oxygen
- @ 10 mins: lose ability to contract
- @ 20 min: necrosis begins
What are 4 conditions that increase oxygen demand to the heart?
- High systolic BP
- Increased ventricular volume
- Increased thickness of the myocardium
- Increased HR
Healthy coronary a. are able to _____ to (increase/decrease) the flow of oxygenated blood to the _____.
Healthy coronary a. are able to dilate to increase the flow of oxygenated blood to the myocardium.
Narrowing the coronary a. by ___% impairs the flow enough to affect the cell during exertion.
Narrowing the coronary a. by 50% impairs the flow enough to affect the cell during exertion.
What is angina pectoris?
Chest pain caused by myocardial ischemia
What causes the actual pain during angina pectoris?
Buildup of lactic acid
Abnormal stretching of the ischemic m.
What disorders are associate with angina pectoris?
What are the two types of angina?
What causes stable angina? Is it predictable?
Luminal narrowing and hardening of the arterial walls (atherosclerosis)
What causes unstable angina? Is it predictable?
Combination of vasospasm and atherosclerotic lesions
Unpredictable; often occur at rest
What are some factors that affect the clinical presentation of ischemic disease?
Type (Fibrolipid plague more likely to rupture)
Speed @ which it develops
Extent of disease in other branches
Other diseases that increase oxygen demand
What factors can drugs target to help with myocardial ischemia?
L. ventricular volume
The goal is to reduce oxygen consumption of the myocardium.
What is MI?
Myocardial infarction is prolonged ischemia (>20 min) which leads to irreversible hypoxic injury, cellular death, and tissue necrosis.
Where does necrosis begin with MI?
Necrosis begins in the subendocardial region and extends in the next 3-6 hrs.
Can ischemic tissue around necrosis be healed?
Ischemic tissue around the area of necrosis may or may not be irreversibly damaged at the outset.
MI leads to glycolysis (use of glycogen stores for energy) which then causes what?
Accumulation of hydrogen ions and lactic acid, causing acidosis and eventual heart failure
Oxygen deprivation that occurs with MI also causes what?
Electrolyte imbalance which excites the myocardium leading to dysrhythmias (90% of individuals w/ MI).
What functional changes occur as a result of MI?
Decreased contractility, SV, and ejection fraction
Increased end-systolic volume
SA node malfunction
List the 4 main coronary a.
Where does occlusion of the RCA cause infarction?
30% of all cases
Where does occlusion of the LCX cause infarction?
20% of all cases
Where does the occlusion of the LAD cause infarction?
Anterior infarction (widowmaker)
50% of all cases
Where does occlusion of the l. coronary a. cause infarction?
What affects the ability to repair an infarct? Is there inflammation?
The site and size of the lesion
MI causes a sever inflammatory reaction
What are the problems with collagen repair of infarcts?
Collagen matrix that is initially deposited is weak and may be stressed within 10-14 days post-infarct
After 6 weeks, necrotic area is replaced by scar tissue, which cannot contract and relax (non compliant) like healthy heart tissue
When do infarcts typically rupture?
May occur anytime within the first 2 weeks (usually between days 4-7)
What percentage of MI cases lead to rupture? What does rupture often cause?
13% of MI cases lead to rupture
Rupture of an infarct often leads to fatal cardiac tamponade (hemopericardium)
What are some clinical manifestations of MI?
Sudden chest pain
Increased creatine kinase and lactic dehydrogenase
When are patients at the highest risk for sudden death?
Within the first 24 hours after onset.
What are some treatments of MI?
Aspirin (inhibits platelets)
Bed rest w/ gradual return to activities
What is the most common complication associate with MI?
What percentage of MI cases result in sudden coronary death?
Describe the normal conduction system of the heart
SA Node - atria - AV node - AV bundle - R & L bundle branches - purkinje fibers
What does it mean that cardiac myocytes are autorhythmic?
They depolarize at regular time intervals without external stimulation
Cardiac m. is an excitable tissue
What is a sinus rhythm?
A normal cardiac rhythm, originates at SA node
_____ can be caused by abnormal rate or the abnormal conduction of impulses.
Arrythmias can be caused by abnormal rate or conduction.
What does the seriousness of an arrythmia depend on?
Its hemodynamic consequences (how much it affects blood flow)
Valvular damage can be either congenital or ____.
Valvular damage can be either congenital or acquired.
What can cause acquired valvular dysfunction?
Abnormal valves are more susceptible to ____.
Abnormal valves are more susceptible to infection,
What are 3 hemodynamic burdens that occur with abnormal valves?
What is valvular stenosis?
Valve orifice is constricted and narrowed, impeding the forward flow of blood
What do pressure increases in a chamber (like with valvular stenosis) cause?
Myocardial hypertophy - cardiomegaly
What are the consequences of valvular dysfunction?
Changes in pre/afterload
Decreased contractility and ejection fraction
Increased diastolic pressure
Ventricular failure from overworking
How does one get rheumatic heart disease?
It is immunologically mediated.
3% of strep (sequella of group A) leads to acute rheumatic fever; 10% of ARF cases lead to rheumatic heart disease
Rheumatic heart disease happens in ____ episodes.
Rheumatic heart disease happens in recurrent episodes.
What is rheumatic heart disease?
Acute carditis +
Chronic valvular deformities
What are some examples of ventricular escape beats?
Does calcific aortic stenosis occur gradually or acutely?
Gradually, often age-related
What is MV prolapse?
Cusps of the MV "billow upward" or prolapse into the atrium during systole
Cusps become thickened
Patients may request antibiotics before dental work
Elongated chordae tedinae are often seen with what?
MV prolapse has a high incidence in whom?
What is infective (bacterial) endocarditis?
Masses of thrombotic debris and organisms infect the aortic and mitral valves
Why is infective endocarditis hard to treat?
Because of the avascular nature of valves, antibiotics can't reach
What are the 2 forms of bacterial endocarditis?
- Acute: organisms with high virulence
- Subacute: organisms of lower virulence
What is virulence?
The strength, potency, or danger of a pathogen
What are some conditions that increase the risk of infective endocarditis?
IV drug abuse and indwelling catheters
Chronic valve diseases
Describe the etiology of infective endocarditis
Infection occurs when organisms are implanted on the endocardial surface during episodes of bacteremia
Describe the steps of the pathogenesis of endocarditis
Bacteria erode endothelium
Site of injury covered with fibrin/platelet clot
Inflammatory cells and bacteria invade the thrombus
Bacteria invade valves and destroy connective tissue
Inflammation heals by fibrosis causing deformity and vegetations
What are some clinical features of bacterial endocarditis?
Cardiac murmurs (most characteristic)
Negative blood cultures
May result in CHF and valvular regurgiation/stenosis
(was almost always fatal before antibiotics)
What is myocarditis and what are the different etiologies?
Heart wall inflammation
Viruses (most common)
Cardiac allograft rejection
What are the 2 types of pericarditis?
- Primary: uncommon, usually infectious
- Secondary: due to MI, cardiac surgery, radiation
What are the possible outcomes of pericarditis?
Resolution without complication
progress to chronic fibrosis
What are cardiomyopathies and what is the etiology?
Heart diseases resulting from a primary abnormality in the myocardium
What are the 3 major froups of cardiomyopathies?
What is dilated cardiomyopathy?
Progressive dilation of the chambers leading to weak contractions
Associated with alcohol abuse, toxic insult, or viral
What is hypertrophic cardiomyopathy?
Thickened walls leading to abnormal ventricular diastolic filling
Ineffective ejection because EDV is so small
What is restrictive cardiomyopathy?
Decrease in ventricular compliance
Inelastic ventricle leading to EDV and SV
What can all 3 cardiomyopathies lead to?
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