06 PV Loop

PV Loops

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• volume on bottom, pressure on top

• right: take volume and pressure of each time and plot against one another

• green: volume not changing, pressure go way up, isovolumic contraction. Both valves closed

• top left point: end of systole

• bottom right point: end of diastole

• left line: end systolic pressure volume relationship, determined by myocardium characteristics. Adding/removing blood at end of systole moves along this line

• right line: end diastolic pv relationship

• MV closes at beginning of isovolumic contraction

• pressure so high aortic valve opens

• volume falls in LV, blood leaving

• AV open, contraction

• AV closes, isovolumic relaxation

• MV opens

• SV: difference between ESV and EDV, volume ejected

• more afterload, higher pressure LV has to rise to overcome

Changes

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• hit left line sooner, at higher volume and pressure

• harder to eject blood, eject less blood

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• contractility determines ESPVR

• less contractility, less blood pushed out, more blood left behind

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• compliance determines preload

• ventricle cannot fill and stiffer, higher pressure, lower volume

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• area: how much volume pumping x how much pressure generating

Pathology

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• higher afterload, lower SV, higher ESV

• during isovolumic contraction, blood leak from LV to LA, falling

• blood filling ventricle during relaxation

• just slightly smaller