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(Hypertension. 2007;49:e8.)
© 2007 American Heart Association, Inc.

Letters to the Editor

Letter to the Editor

Response to Arterial Stiffness Index Is Not a Stiffness Parameter But a Ventriculo-Arterial Coupling Factor

Shanghai Institute of Hypertension, Shanghai Jiaotong University Medical School, Shanghai, China

Eamon Dolan

Cambridge University Hospital, Addenbrooke’s Hospital, Cambridge, United Kingdom

Eoin O’Brien

Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland

Tine W. Hansen; Hans Ibsen

Copenhagen University Hospital, Copenhagen, Denmark

Masahiro Kikuya; Yutuka Imai

Tohoku University Graduate School of Pharmaceutical Science and Medicine, Sendai, Japan

Tom Richart; Lutgarde Thijs; Jan A. Staessen

Division of Hypertension and Cardiovascular Rehabilitation, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium

An extract of the first 250 words of the full text is provided, because this article has no abstract.

We defined the ambulatory arterial stiffness index (AASI) as unity minus the regression slope of the brachial diastolic on systolic blood pressure.^1,2 AASI, therefore, models the dynamic relation between diastolic and systolic pressure throughout the day. We concur with Westerhof et al³ that AASI is an indirect measure of arterial stiffness. Several hemodynamic factors influence AASI, including ventriculo-arterial coupling. In this regard, AASI does not differ from other measures of arterial stiffness, including pulse wave velocity, which many experts consider as the gold standard.

To further assess the physiological meaning of AASI, we partially implemented the proposal of Westerhof et al.³ We computed in our 348 Chinese subjects¹ the decay time of aortic pressure during diastole (). We rewrote as [(60xmean arterial pressure)/(heart ratexpulse pressure). We averaged the values obtained from the blood pressure readings in each 24-hour ambulatory recording. Across our study sample,¹ was normally distributed (Shapiro–Wilk’s W, 0.995; P=0.34), averaging (SD) 1.84 (0.29) seconds. We found an inverse association (r=–0.21; P<0.0001) between and AASI (Figure), which strengthens the concept that AASI is a measure of arterial stiffness. In the final formula, Westerhof et al³ defined the slope of diastolic on systolic blood pressure as the ratio of diastolic to systolic blood pressure and, therefore, assumed an intercept of 0. We did not force the regression line through the origin,^1,2 because during diastole, when blood flow drops to 0, this is not the case for blood pressure.

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