09 Starling

Starling Curve

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• preload can be either pressure or volume

• the more you load the ventricle with fluid, the more it'll pump

• allows heart to pump with higher venous return, otherwise blood would pool in venous system

• shifting to left: at same preload, more stroke volume

• TPR = SVR = peripheral resistance

Venous Return

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• venous return = CO: blood returned to heart = blood pumped out of heart

• X axis could be either venous return or CO

• as CO increases, RAP falls

• RAP equal to venous pressure from SVC/IVC

• Increased CO: pulls more blood out of RV/RA, lowers RA pressure

• how actually drawn

• MSFP defined by volume in venous system and tone of veins in body

• MSFP = pressure when CO is 0

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• green: right shift

• increased TPR: same CO leads to lower venous pressure and lower RAP

Combined Curves

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HF

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• lower contractility: shift to right of starling curve

• fluid retention: increased fluid volume, shift venous return curve right

• increased TPR: changes slope of venous return curve

• lower CO and higher RAP

Hemorrhage

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• blood loss: shift venous return left

• TPR up: slope left

• contractility: starling curve up

• lower CO, lower RAP

Exercise

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• venous contraction from sympathetic activation

• venous contraction: move to right

• decreased TPR: slope right

• higher CO in exercise

Fistula

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• same as exercise

• high output heart failure

• nl: arteriole connectes arteries and veins. Arteries have high resistance

• AV: bypass from A to V with low resistance

• result: TPR down

Vasopressors

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