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Cardiovascular Physiology

A 42-year-old woman with mitral prolapse is admitted to the hospital for evaluation of her cardiac function. Which of the following values is the best index of the preload on her heart?

ExplanationPreload is the degree to which the myocardium is stretched before it contracts, i.e., the length of the sarcomere at the end of diastole. In vivo, the variable most directly related to sarcomere length during end-diastole is left ventricular end-diastolic volume. Although blood volume, central venous pressure, pulmonary capillary wedge pressure, and left ventricular end-diastolic pressure can all influence preload, they all exert their influence through changes in end-diastolic volume.