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Intuidvely preload stretch from the muscle bers

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Unformatted text preview:   SV depends on preload, a\erload and contracDlity Review: Preload and A\erload •  Preload and A\erload = wall tension during diastole and systole, respecDvely. IntuiDvely: –  Preload = stretch from the muscle fibers; approximated by EDV or EDP –  A\erload = resistance that must be overcome to eject LV blood; approximated by ESP –  Wall stress, S = (P x r)/2w; where r = LV radius, w=wall thickness (rewriDng the LaPlace equaDon P=2Sw/r) •  From cardiac PV loop, see that the major change during diastole is volume; whereas major change during systole is pressure •  Therefore, lowering blood pressure reduces a\erload; lowering EDV reduces preload Cardiac Output or Stroke Volume Review: Frank Starling Curve; Note Changes with Increased or Decreased ContracDlity 2 4/9/13 Heart Failure •  •  Inability to pump blood to meet the metabolic demands (forward failure), or at least do so only in presence of abnormally high filling pressures (backward failure). CulminaDon of various pathologies –  LV pathology, systolic dysfuncDon –  Impaired filling, dias...
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