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13 Cards in this Set
- Front
- Back
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What is the pathogenesis of atherosclerosis?
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Endothelial injury causes LDL to accumulate in macrophages and migrate below the internal elastic membrane. Endothelial cells and activated macrophages release growth mactors and cause platelet adherence. Lipid core and fibrin accumulation forms.
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How is bloodflow regulated in the normal myocardium?
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Q=(Pin-Pout)/R, with the most resistance located in the arterioles.
During increased cardiac need, the capillaries can dilate to increase flow. Myocardial demand is balanced with myocardial supply. |
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How does cardiac bloodflow regulation change in coronary stenosis?
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A new site of resistance forms at the site of stenosis. To compensate, the vessels distal to the stenosis dilate to imcrease flow. This allows a balance between oxygen supply and demand, but reduces the reserve of dilation.
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What is the coronary steal phenomenon?
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The heart compensates for coronary stenosis by vasodilation. More dilation occurs in arteries closer to the endocardium, and less so in arteries closer to the epicardium. Addition of pharmacological vadodilators will cause the myocardial vessels to dilate more. This will "steal" blood away from the endocardium and can worsen ischemia.
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What are the 5 main determinants of myocardial oxygen consumption?
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Ventricular systolic pressure***
Stroke volume Heart rate *** LV chamber radius Contractility |
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What is the equation for myocardial oxygen consumption?
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O2 consumption = LV systolic pressure * heart rate
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What are the clinical presentation of myocardial ischemia?
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Pressure on chest
Crushing pain Referred pain down left shoulder and arm Variable in women |
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What are precipitating factors often found with MIs?
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Exertion
Pain reduces when stimulus removed Exercise intolerance |
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How does the heart compensate for an MI?
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Sympathetic stimulation of viable myocardium to establish normal MAP.
Area surrounding the ischemia becomes hyperfunctional. Sympathetic stimulation causes increased energy demand on the heart. Can result in return to normal or toward heart failure. |
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What can be the consequences of an MI?
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Reduced CO, heart failure
Arrythmia Cardiac rupture Edema Papillary muscle repture |
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How do coronary collateral circulation form?
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Develop in response to coronary stenosis and myocardial ischemia to provide blood flow.
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What are the limitations of collateral circulation?
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MI, angina can occur during periods of increased myocardial work and stress.
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What are the benefits of an exercise training program in coronary disease?
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Improved coronary flow
Decreased ischemia Enhanced angiogenesis Growth factor interactions Collateral development |
