Term
| When does coronary artherosclerosis become symptomatic? |
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Definition
| when 70% of the lumen is occluded |
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Term
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Definition
(perfusion pressure)/ (R due to clot + R due to vessels)
*resistances are in series; heart compensates for resistance from clot by vasodilating i.e. reducing vessel resistance |
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Term
| When does coronary artherosclerosis become symptomatic AT REST? |
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Definition
| with severe obstruction such as more than 90% of the vessel |
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Term
| How long can the heart use creatine phosphate and ATP stores once there is ischemic event? |
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Definition
| first 30 seconds of normal contractile activity. With SEVERE ischemia, creatine phosphate is depleted within a few seconds |
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Term
| In canine myocardial ischemia studies, ATP decreases to _% of control by 15 minutes and _% of control after 40 minutes. |
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Definition
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Term
| Does the heart produce or extract lactate from the blood? |
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Definition
| normally extracts but during ischemia heart is net producer of lactate |
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Term
| How many ATP does anaerobic glycolysis produce? oxidative metabolism? |
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Definition
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Term
| Even under conditions of maximal stimulation, anaerobic glycolysis can produce __% of the HEP necessary for a normal working heart. |
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Definition
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Term
| What effect on shortening does a decrease in blood flow from 1-70% have? |
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Definition
| parallel decrease in shortening (hypokinesis) |
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Term
| What effect on shortening does a decrease in blood flow of 80% have? |
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Definition
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Term
| What effect on shortening does a decrease in blood flow of more than 90% have? |
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Definition
| dyskinesis (paradoxical lengthening) |
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Term
| WHat is the mechanism behind the decrease in blood flow effect on shortening of cardiac myocytes? |
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Definition
| not well defined. Definately NOT the result of HEP depletion but might be due to alterations in intracellular calcium handling, developing intracellular acidosis and accumulation of fatty acids (lipid breakdown) |
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Term
| T/F Myocardial ischemia affects the normal function of the heart during diastole. |
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Definition
| true: ischemia impairs relaxation and makes the ventricle stiffer which impairs ventricular filling and further impairs cardiac output |
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Term
| What is myocardial stunning? |
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Definition
| prolonged yet reversible systolic dysfunction of the heart following a period of ischemia |
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Term
| Clinically, myocardial stunning most likely occurs in patients who... |
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Definition
| subsequent to ischemic cardiac arrest (during surgical/bypass procedures), following thrombolysis during an acute myocardial infarction (affects the viable myocardium adjascent to the infarcted tissue), following therapeutic ballooon angioplasty, or in pts with vasospastic angina and/or unstable angina |
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Term
| What is myocardial hibernation? |
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Definition
| chronic mechanical dysfunction (wall motion abnormality) subsequent to chronic,severe ischemia (i.e. high grade coronary stenosis) The wall motion abnormality is restored to normal upon restoration of blood flow |
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Term
| Compare and contrast myocardial stunning versus myocardial hibernation. |
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Definition
| in myocardial stunning there is mismatch between flow and function for a period of days while blood flow and function are matched for myocardial hibernation. However there is no irreversible injury/necrosis associated with EITHER sutnning or hibernation; they are functional deficits |
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