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Ethnic differences in arterial wave reflections and normative equations for augmentation index.

ABSTRACT: Data regarding ethnic differences in wave reflections, which markedly affect the central pressure profile, are very limited. Furthermore, because age, heart rate, and body height are strong determinants of augmentation index, relating single measurements to normative data (in which augmentation index values correspond with average population values of its determinants) is challenging. We studied subject-level data from 10 550 adults enrolled in large population-based studies. In a healthy reference sample (n=3497), we assessed ethnic differences in augmentation index (ratio of second/first systolic peaks) and generated equations for adjusted z scores, allowing for a standardized comparison between individual augmentation index measurements and the normative population mean from subjects of the same age, sex, ethnic population, body height, and heart rate. After adjustment for age, body height, heart rate, and mean arterial pressure, African blacks (women: 154%; men: 138%) and Andean Hispanics (women: 152%; men: 133%) demonstrated higher central (aortic) augmentation index values than British whites (women: 140%; men: 128%), whereas American Indians (women: 133%; men: 122%) demonstrated lower augmentation index (all P<0.0001), without significant differences between Chinese and British whites. Similar results were found for radial augmentation index. Nonlinear ethnic/sex-specific equations for z scores were successfully generated to adjust individual augmentation index values for age, body height, and heart rate. Marked ethnic differences in augmentation index exist, which may contribute to ethnic differences in hypertensive organ damage. Our study provides normative data that can be used to complement the interpretation of individual hemodynamic assessments among men and women of various ethnic populations, after removing the effect of various physiological determinants.

SUBMITTER: Chirinos JA

PROVIDER: S-EPMC3151727 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Ethnic differences in arterial wave reflections and normative equations for augmentation index.

Chirinos Julio A JA Kips Jan G JG Roman Mary J MJ Medina-Lezama Josefina J Li Yan Y Woodiwiss Angela J AJ Norton Gavin R GR Yasmin Van Bortel Luc L Wang Ji-Guang JG Cockcroft John R JR Devereux Richard B RB Wilkinson Ian B IB Segers Patrick P McEniery Carmel M CM

Hypertension (Dallas, Tex. : 1979) 20110502 6

Data regarding ethnic differences in wave reflections, which markedly affect the central pressure profile, are very limited. Furthermore, because age, heart rate, and body height are strong determinants of augmentation index, relating single measurements to normative data (in which augmentation index values correspond with average population values of its determinants) is challenging. We studied subject-level data from 10 550 adults enrolled in large population-based studies. In a healthy refere ...[more]

PMID: 21536986

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Project description:ObjectivesThis study sought to assess the relationship between central pressure profiles and cardiovascular events (CVEs) in a large community-based sample.BackgroundExperimental and physiologic data mechanistically implicate wave reflections in the pathogenesis of left ventricular failure and cardiovascular disease, but their association with these outcomes in the general population is unclear.MethodsAortic pressure waveforms were derived from a generalized transfer function applied to the radial pressure waveform recorded noninvasively from 5,960 participants in the Multiethnic Study of Atherosclerosis. The central pressure waveform was separated into forward and reflected waves using a physiologic flow waveform. Reflection magnitude (RM = [Reflected/Forward wave amplitude] × 100), augmentation index ([Second/First systolic peak] × 100) and pulse pressure amplification ([Radial/aortic pulse pressure] × 100) were assessed as predictors of CVEs and congestive heart failure (CHF) during a median follow-up of 7.61 years.ResultsAfter adjustment for established risk factors, aortic AIx independently predicted hard CVEs (hazard ratio [HR] per 10% increase: 1.08; 95% confidence interval [CI]: 1.01 to 1.14; p = 0.016), whereas PPA independently predicted all CVEs (HR per 10% increase: 0.82; 95% CI: 0.70 to 0.96; p = 0.012). RM was independently predictive of all CVEs (HR per 10% increase: 1.34; 95% CI: 1.08 to 1.67; p = 0.009) and hard CVEs (HR per 10% increase: 1.46; 95% CI: 1.12 to 1.90; p = 0.006) and was strongly predictive of new-onset CHF (HR per 10% increase: 2.69; 95% CI: 1.79 to 4.04; p < 0.0001), comparing favorably to other risk factors for CHF as per various measures of model performance, reclassification, and discrimination. In a fully adjusted model, compared to nonhypertensive subjects with low RM, the HRs (95% CI) for hypertensive subjects with low RM, nonhypertensive subjects with high RM, and hypertensive subjects with high RM were 1.81 (0.85 to 3.86), 2.16 (1.07 to 5.01), and 3.98 (1.96 to 8.05), respectively.ConclusionsArterial wave reflections represent a novel strong risk factor for CHF in the general population.

Project description:Background Arterial stiffness and earlier wave reflections can increase afterload and impair cardiovascular function. Most prior studies have been performed in patients with preserved left ventricular function. We describe novel measures of pulsatile arterial hemodynamics and their association with clinical outcomes in patients with heart failure with reduced ejection fraction. Methods and Results Participants with heart failure with reduced ejection fraction (n=137, median age 56 years, 49% women, 58% Black) and age-matched healthy controls (n=124) underwent measurements of large artery stiffness and pulsatile arterial hemodynamics. Carotid-femoral pulse wave velocity and augmentation index were assessed using radial applanation tonometry. Pressure-flow analyses derived reflected wave transit time, the systolic pressure-time integral imposed by proximal aortic characteristic impedance, and the pressure-time integral from wave reflection (wasted pressure effort). Cox proportional hazards models defined associations between hemodynamic measures and (1) all-cause death and (2) a combined end point of left ventricular assist device implant, heart transplant, and death, at 2 years adjusted for race, BNP (B-type natriuretic peptide), and the Meta-Analysis Global Group in Chronic Heart Failure Risk Score. Compared with controls, participants with heart failure with reduced ejection fraction exhibited similar carotid-femoral pulse wave velocity (6.8±1.6 versus 7.0±1.6 m/s, P=0.40) but higher augmentation index normalized to a heart rate of 75 bpm (13±2% versus 22±2%, P<0.001). Shorter reflected wave transit time (ie, earlier wave reflection arrival to the proximal aorta) was associated with an increased risk of death (adjusted hazard ratio [aHR] 1.67 [95% CI 1.03-1.63]) and the combined end point of death/left ventricular assist device/heart transplant (aHR, 1.61 [95% CI, 1.06-2.44]) at 2 years. Wasted pressure effort/proximal aortic characteristic impedance, representing the proportion of systolic load from wave reflection versus aortic root characteristic impedance, was univariately associated with death (hazard ratio (HR), 1.44 [95% CI, 1.05-1.97]) and with death/left ventricular assist device/heart transplant on univariate (HR, 1.42 [95% CI, 1.07-1.88]) and multivariable (aHR, 1.40 [95% CI, 1.02-1.93]) analysis. Conclusions Increased left ventricular systolic load from premature wave reflections is associated with adverse clinical outcomes in patients with heart failure with reduced ejection fraction.

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Ethnic differences in arterial wave reflections and normative equations for augmentation index.

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Ethnic differences in arterial wave reflections and normative equations for augmentation index.

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