VALIDATION OF CAROTID-ARTERY TONOMETRY AS A MEANS OF ESTIMATING AUGMENTATION INDEX OF ASCENDING AORTIC PRESSURE

Our objective was to validate a carotid artery tonometry-derived augme ntation index as a means to estimate augmentation index (AI) of ascend ing aortic pressure under various physiological conditions. A total of 66 patients (50 men, 16 women; mean age, 55 years; range, 21 to 78 ye ars; 44 in Taiwan and 22 in the Unites Slates) undergoing diagnostic c atheterization were studied. Arterial pressure contours were obtained simultaneously from the right common carotid artery by applanation ton ometry with an external micromanometer-tipped probe and from the ascen ding aorta by a micromanometer-tipped catheter at baseline (n=62), aft er handgrip (n=36), or after sublingual nitroglycerin administration ( n=17). The Al (expressed as percentage values) was calculated as the r atio of amplitude of the pressure wave above its systolic shoulder to the total pulse pressure. The carotid AI was consistently lower than t he aortic AI, but the two were highly correlated at baseline and after both handgrip and nitroglycerin. Mean+/-SD and correlation coefficien ts 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 Al with appropriate regression equat ions. The high correlations and predictable changes after intervention s between the central AI and those estimated from noninvasive carotid tonometry suggest that this technique may have wide applicability for many cardiovascular studies.