Our objective was to validate a carotid artery tonometry-derived augmentation index as a means to estimate augmentation index (AI) of ascending aortic pressure under various physiological conditions. A total of 66 patients (50 men, 16 women; mean age, 55 years; range, 21 to 78 years; 44 in Taiwan and 22 in the United States) undergoing diagnostic catheterization were studied. Arterial pressure contours were obtained simultaneously from the right common carotid artery by applanation tonometry with an external micromanometer-tipped probe and from the ascending aorta by a micromanometer-tipped catheter at baseline (n = 62), after handgrip (n = 36), or after sublingual nitroglycerin administration (n = 17). The AI (expressed as percentage values) was calculated as the ratio of amplitude of the pressure wave above its systolic shoulder to the total pulse pressure. The carotid AI was consistently lower than the aortic AI, but the two were highly correlated at baseline and after both handgrip and nitroglycerin. Mean +/- SD and correlation coefficients were baseline (14 +/- 16, 28(+) +/- 17, .77), handgrip (18 +/- 19, 32(+) +/- 15, .86), and nitroglycerin (7 +/- 12, 18(+) +/- 13, .52). In addition, after adjusting for age, sex, height, blood pressure, heart rate, and study site, the changes of both AIs from baseline values with handgrip or nitroglycerin were highly associated such that the aortic AI could be approximated from the carotid AI with appropriate regression equations. The high correlations and predictable changes after interventions between the central AI and those estimated from noninvasive carotid tonometry suggest that this technique may have wide applicability for many cardiovascular studies.

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A substantial proportion of measured resting left ventricular diastolic pressure stems from forces extrinsic to the left ventricle rather than from diastolic stiffness in the left ventricle itself. This markedly influences the dependence of cardiac output on filling pressure and has important implications for clinical application of the Starling law.

A reduction in upright exercise capacity with aging in healthy individuals is accompanied by acute left ventricular (LV) dilatation and impaired LV ejection. To determine whether acute vasodilator administration would improve LV ejection during exercise, sodium nitroprusside (NP) was administered to 16 healthy subjects, ages 64-84 yr, who had been screened for the absence of coronary heart disease by prior exercise thallium scintigraphy. Infusion of NP (0. 3-1.0 microgram. kg(-1). min(-1)), titrated to reduce the resting mean arterial pressure 10% (and eliminate the late augmentation of carotid arterial pressure), increased LV ejection fraction (EF) compared with placebo during upright, maximal graded cycle exercise at all work rates and permitted an equivalent stroke volume and stroke work from a smaller end-diastolic volume. The maximum increase in exercise EF in older subjects during NP infusion was equal to that in healthy, younger (22-39 yr) control subjects. The maximum cycle work rate and cardiac index were unchanged compared with placebo. Thus combined preload and afterload reduction with NP in older individuals improves overall LV ejection phase function: exercise LV stroke work is reduced, EF is increased, and stroke volume is maintained in the setting of a reduced ventricular size. These findings suggest that at least some of the age-associated decline in cardiac function during maximal aerobic exercise may be secondary to adverse loading conditions.

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