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27 Cards in this Set
- Front
- Back
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How is left ventricular stroke work determined?
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SV x LV pulse pressure(or mean arterial pulse pressure)
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What are the 3 factors that affect Stroke volume and therefor CO?
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Contractility, preload, afterload
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How does the ANS indirectly affect the stroke volume?
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ANS can affect contractility of myocardium
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What is the major contributing factor to preload?
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venous return
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What factors can affect preload?
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filling time\pressure, compliance, atrial systole, pericardial constraint
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What factors affect afterload?
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peripheral pressure, arterial compliance, blood viscosity, valve function
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What factors can affect Contractility?
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ANS/hormones and Treppe
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What is the definition of preload?
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Tension in ventricular wall at end of diastole
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What does preload determine?
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Resting fiber length
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What did Frank starling theorize?
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The increase ventricular contraction energy is a function of fiber length
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What is ventricular filling time most dependent on?
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Heart rate
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When is atrial systole most important?
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When filling time is reduced
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How can Cardiac output be maintained in the face of reduced filling time?
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Increased heart rate to compensate for lower SV, Sympathetic stimulation increases contractility ie inc ejection fraction
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How is compliance determine?
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∆V\∆P
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What conditions cause reduced compliance?
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Ischemia, hypertrophy
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If ventricular pressure are maintained(ie not compliance issues) how can central venous pressure affect SV?
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Increased CVP will increase RV preload and SV which will increase LV
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If ventricular pressure are maintained(ie not compliance issues) how can lower intrathoracic pressure affect SV?
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Decrease ITP will increase RV preload and SV which will increase LV
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What 2 factors can increase the RV pressure and stroke volume?
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Intrathoracic pressure and Central Venous pressure
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How much of EDV is due to atrial systole\"kick"?
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20-30%
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Can atrial contractility increase
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yes, useful if ventricular filling time is low
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Why does pericardial fluid cause decreased compliance?
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Increased pericardial fluid increases hydrostatic pressure
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What are 2 roles of pericardium in cardiac performance?
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Prevents ventricular overfilling, maintains vessel alignment
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What 2 factors does a high afterload cause a decrease in?
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Stroke volume and maximum velocity of ejection
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What 5 things can increase afterload?
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Aortic stenosis, PVR, elevated arterial pressure, inc blood viscosity, decreased arterial compliance
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How is increased afterload compensated for?
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Increased ESV plus normal filling of ventricles increases EDV which increases stroke volume to normal
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How is ventricular stroke work determined graphically?
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The area of the P\V loop
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What increases in the example of increased afterload compensation where EDV is increased to maintain SV?
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Increase ventricular stroke work
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