Problem: A 70-year-old woman comes to the physician for a routine health maintenance examination. She reports no problems. her pulse is 90/min, respirations are 16/min, and blood pressure 160/85 mm Hg. Physical examination shows no abnormalities. Auscultation shows no murmurs, gallops, or bruits, the lungs are clear. Compared with a healthy 40-year-old woman, a change in which of the following best explains blood pressure reading in this patient at this time? Aortic compliance Cardiac index Heart rate Left ventricular chamber diameter Myocardial nonepinephrine concentration