Chapter_16_Mechanical_Aspects_of_Cardiac_Performance__1_slide_per_page

Chapter_16_Mechanical_Aspects_of_Cardiac_Performance__1_slide_per_page

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Chapter 16: Mechanical Aspects of Cardiac Performance The parts of the heart normally beat in an orderly sequence: 1) contraction of the atria ( atrial systole ) 2) contraction of the ventricle ( ventricular systole ) 3) during diastole, the ventricles are relaxed BE501 T. K. Hsiai, MD, PhD, FACC Objectives
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Cardiac Performance: preload and afterload From molecular to cellular and macrostructures Stretch the muscle to desired length by hanging appropriate weight ( preload ° at the end of ventricular filling ) from the relaxed muscle. The desired preload is determined for the passive length:force relationship . a) Place a support beneath the muscle to allow additional weights ( afterload ° in the intact heart just before opening of the aortic valve ) to be added without stretching the muscle. b) Stimulate the muscle electrically. c) Record change in muscle length once muscle generates sufficient force to lift total load ( preload + afterload). d) Repeat series for different afterloads.
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