CONTRACTILITY Inherent property of the myocardium Allows the
heart to increase its extent and force of shortening independent of
the Starling mechanism Not directly measurable
STARLINGS LAW THE MORE A MYOCARDIAL FIBER IS STRETCHED DURING
DIASTOLE, THE MORE IT WILL SHORTEN IN SYSTOLE IT WILL ALSO SHORTEN
WITH GREATER FORCE
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PRELOAD The length to which a cell is stretched prior. To the
next contraction The volume or pressure generated in the ventricles
at end-diastole Degree to which a cell is stretched in diastole
(preload) force during systole
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AFTERLOAD IMPEDANCE OF BLOOD FROM THE VENTRICLE Determined by:
The volume and mass of blood ejected from the ventricle The
compliance and total cross-sectional area of the vascular space
into which the blood is ejected.
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AFTERLOAD RESISTANCE PROXIMAL IMPEDENCE
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SYSTEMIC VASCULAR RESISTANCE SVR= (MAP-RAP) (80) CO MAP= MEAN
ARTERIAL PRESSURE RAP= RIGHT ATRIAL PRESSURE CO= CARDIAC
OUTPUT
Clinical Profile of Nesiritide Vasodilation (venous >
arterial) Rapidly improves symptoms of congestion Does not increase
heart rate (decreases myocardial oxygen demand) Is not
proarrhythimic Neurohormonal suppression (decreases aldosterone,
endothelin-1) Mild diuresis/natriuresis
Slide 24
Clinical Profile Nesiritide (cont.) No evidence of
tachyphylaxis Symptomatic hyptension as low as 4% in the VMAC study
Dosing convenience (bolus plus standard- dose IV infusion