Measurements of arterial stiffness: Are they ready for clinical use?
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Corresponding author Michel E. Safar, MD Paris Descartes University, Diagnosis Center, Hôtel-Dieu, 1, Place du parvis Notre-Dame, 75181 Paris Cedex 04, France. E-mail: [email protected] Current Cardiovascular Risk Reports 2008, 2:268 –273 Current Medicine Group LLC ISSN 1932-9520 Copyright © 2008 by Current Medicine Group LLC
For many years, the role of mechanical factors in cardiovascular (CV) epidemiology has been based on the description of linear relationships between CV events and the level of systolic and diastolic blood pressure. Systolic and diastolic blood pressure are simply the highest and lowest points of the cyclic blood pressure curve, which questions the validity of simple linear or semilogarithmic models for the statistical evaluations of CV risk. Recently, epidemiologic studies relating mean and pulse pressure to the occurrence of CV events have been proposed and applied to the understanding of pulse pressure, arterial stiffness, and wave reflections in the mechanisms of human hypertensive complications. This article underscores the deficiencies of auscultatory brachial artery pressure and describes the methodology of other newly developed hemodynamic models. It also describes their applications to CV risk prediction and attempts to place them in a clinical context.
Introduction Brachial artery (BA) pressure as measured by the auscultatory method has been of incalculable value in clinical medicine, initially providing numeric data for the diagnosis and screening of hypertension. More recently, the method has been used for the assessment of cardiovascular (CV) risk in therapeutic analyses and meta-analyses of large populations, but these studies have raised several major questions. First, for risk assessment especially in patients older than 55, diastolic blood pressure (DBP) is less useful because it falls with aging [1], leaving the systolic blood pressure (SBP), pulse pressure (PP), or the mean blood pressure (MBP) as remaining candidates for the evaluation of CV risk [2]. Second, because the conventional brachial SBP and PP often differ from aortic pressures due to pulse amplification, they are not reliable
surrogates for aortic or carotid pressures [3]. Finally, aortic pressures, not the BA pressures (against which the heart pumps), are best suited for cardiac risk assessment, and carotid arterial pressures (almost identical to aortic pressures) are best suited for stroke risk assessment. Together, these observations suggest that studies based on pulsatile arterial and aortic hemodynamics should be an improvement over BA pressure alone in assessing CV risk. We review the liabilities of the time-honored but limited auscultatory BP measurement, and we discuss the pathophysiology of the arterial tree and how it can be applied to improvements in the measurement of the systemic BP.
From BP to Pulsatile Arterial Hemodynamics The standard auscultatory method of measuring BP defi nes hypertension from only two points on the pulsatile pressure curve: peak SBP and end DBP [2 ,4, 5]. It now appea
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