Noninvasive Assessment of Arterial Stiffness Should Discriminate Between Systolic and Diastolic Pressure Ranges

Abstract

Abstract-Arterial stiffening plays an important role in the development of hypertension and cardiovascular diseases. The intrinsically nonlinear (ie, pressure-dependent) elastic behavior of arteries may have serious consequences for the accuracy and interpretation of arterial stiffness measurements and, ultimately, for individual patient management. We determined aortic pressure and common carotid artery diameter waveforms in 21 patients undergoing cardiac catheterization. The individual pressure-area curves were described using a dual exponential analytic model facilitating noise-free calculation of incremental pulse wave velocity. In addition, compliance coefficients were calculated separately in the diastolic and systolic pressure ranges, only using diastolic, dicrotic notch, and systolic data points, which can be determined noninvasively. Pulse wave velocity at systolic pressure exhibited a much stronger positive correlation with pulse pressure (PϽ0.001) and age (Pϭ0.012) than pulse wave velocity at diastolic pressure. Patients with an elevated systolic blood pressure (Ͼ140 mm Hg) had a 2.5-times lower compliance coefficient in the systolic pressure range than patients with systolic blood pressures Ͻ140 mm Hg (Pϭ0.002). Most importantly, some individuals, with comparable age or pulse pressure, had similar diastolic but discriminately different systolic pulse wave velocities and compliance coefficients. We conclude that noninvasive assessment of arterial stiffness could and should discriminate between systolic and diastolic pressure ranges to more precisely characterize arterial function in individual patients. Key Words: arterial structure and compliance Ⅲ pulse wave velocity Ⅲ blood pressure measurement Ⅲ systolic hypertension Ⅲ carotid arteries D ecreased elasticity of the arterial wall plays an important role in the development of hypertension and related cardiovascular complications, such as heart failure, stroke, and renal failure. 1-4 Therefore, noninvasive assessment of arterial stiffness has recently entered the European Society of Hypertension/European Society of Cardiology guidelines for the management of hypertension. 5 Basic studies have shown that the elastic behavior of the arterial system is nonlinear, that is, arterial stiffness is pressure dependent. 6 -11 This intrinsic property of the arterial system may have serious consequences for the quantitative assessment of arterial stiffness, and changes therein, in response to age, 12,13 physiological stress, 7 and possibly antihypertensive treatment. 14,15 Currently, arterial stiffness is assessed noninvasively either at the diastolic pressure level (aortic or carotid-femoral pulse wave velocity [PWV]) or estimated as an average over the diastolic-systolic pressure range. In the latter case, distensibility and compliance coefficients are calculated as, respectively, the relative and absolute changes in the cross-sectional area normalized to pulse pressure from diastolic minimum to systolic peak, 16 tacitly assuming a linear pressure-area relatio...

Aortic-Brachial Pulse Wave Velocity Ratio: A Measure of Arterial Stiffness Gradient Not Affected by Mean Arterial Pressure

“…For example, the increase in pressure from diastolic pressure to systolic pressure during a single cardiac cycle could result in a variation of 0.7-4 m/s of PWV (i.e., without any change in vascular wall property) [9,10]. This variability is mainly caused by the organization of elastin, collagen, and vascular smooth muscle cells of the media.…”

“…1). Indeed, a steeper slope in pressure-diameter relationship is observed in the elderly compared to younger individuals as pressure dependence varies with age, due partly to the age-related material fatigue, fractures in the elastin lamella, and vascular fibrosis [9,10,15]. …”

The change in arterial stiffness over the cardiac cycle rather than diastolic stiffness is independently associated with left ventricular mass index in healthy middle-aged individuals

“…Arterial elastic behavior, however, is pressure dependent [8][9][10], which may render aPWV, as estimate of diastolic stiffness, less suitable to reflect effective cardiac afterload. Moreover, we previously demonstrated that the degree of the pressure dependency of arterial stiffness may vary considerably between individuals [11], illustrating the need for individualized assessment of this property.…”

Vascular Smooth Muscle Activation Improves Aortic Compliance with Respect to Mechanical Loading

“…The relationship between aortic pressure and size is known to be non-linear and single or dual exponential functions were employed elsewhere. 19,22 However, our choice allows the separation between elastin and collagen regions that is consistent with the structural elements of the wall reflected in serial or parallel hook-on arrangement models. 2,27 The linear regression models for the elastin and collagen regions were adjusted to the pressure-diameter curves with high correlation coefficients (always above 0.9).…”