Young African-American men have altered macrovascular and microvascular function.

In this cross-sectional study, we tested the hypothesis that vascular dysfunction in young African-American men would contribute to greater central blood pressure (BP) compared with young white men.

Fifty-five young (23 yr), healthy men (25 African-American and 30 white) underwent measures of vascular structure and function, including carotid artery intima-media thickness (IMT) and carotid artery β-stiffness via ultrasonography, aortic pulse wave velocity, aortic augmentation index (AIx), and wave reflection travel time (Tr) via radial artery tonometery and a generalized transfer function, and microvascular vasodilatory capacity of forearm resistance arteries with strain-gauge plethysmography.

African-American men had similar brachial systolic BP (SBP) but greater aortic SBP (P < 0.05) and carotid SBP (P < 0.05). African-American men also had greater carotid IMT, greater carotid β-stiffness, greater aortic stiffness and AIx, reduced aortic Tr and reduced peak hyperemic, and total hyperemic forearm blood flow compared with white men (P < 0.05). In conclusion, young African-American men have greater central BP, despite comparable brachial BP, compared with young white men. Diffuse macrovascular and microvascular dysfunction manifesting as carotid hypertrophy, increased stiffness of central elastic arteries, heightened resistance artery constriction/blunted resistance artery dilation, and greater arterial wave reflection are present at a young age in apparently healthy African-American men, and conventional brachial BP measurement does not reflect this vascular burden.

augmentation index; arterial stiffness

African-American men develop high blood pressure (BP) sooner, and this may manifest as early as their second decade of life (23).

Measurement of central BP has been suggested to hold greater prognostic capability than conventional brachial BP (40). In end-stage renal disease, carotid BP is a stronger predictor of all-cause mortality than brachial BP (65).

Recent findings from the Strong Heart Study have confirmed that central BP is more strongly related to vascular hypertrophy, extent of atherosclerosis, and cardiovascular events than brachial BP (63).

Moreover, central BP is a better predictor of coronary artery disease severity and adverse cardiovascular events than brachial pressure (14, 70).

Increases in carotid BP directly contribute to increases in carotid intima-media thickness (IMT) (69), a reflection of subclinical vascular target-organ damage and an independent risk factor for cardiovascular disease (34, 55).

At present, no study has examined central BP in young African-American males.

One consequence and/or potential mechanism of hypertension is detrimental alterations in vascular structure and function.

Arterial compliance reflects the ability of an artery to expand and recoil in response to cardiac systole and diastole, allowing blood flow to be converted from an intermittent, pulsatile flow to a more steady and laminar flow.

Increases in arterial stiffness and loss of this dampening effect may cause microvascular damage (49, 57) and hasten the atherosclerotic process, regardless of age (38, 58). Consequently, increased arterial stiffness (41, 47), reduced microvascular reactivity (32), and increased subclinical atherosclerosis (34) have been identified as risk factors for future cardiovascular events, as well as the development of hypertension (47).

African-Americans have diffuse macrovascular and microvascular dysfunction manifesting as increased stiffness (reduced compliance) of elastic central arteries, such as the carotid artery and aorta (19, 21, 30), heightened resistance artery constriction, and blunted resistance artery dilation (67).

The greater vascular stiffness and microvascular dysfunction seen in African-Americans are directly related to target organ damage (12, 68).

Carotid IMT is greater in African-Americans compared with white Americans (16, 43). Although vascular dysfunction is considered a function of the aging process, "premature arterial senility" (56) has been reported in normotensive African-American men as young as 21 yr of age (30, 75).

Central BP is influenced by arterial stiffness and microvascular function. Given the known vascular dysfunction in young African-American men, it is possible that central BP may be greater in African-American men, and changes in central BP may precede changes in peripheral (i.e., brachial) BP in this cohort.

Therefore, the primary purpose of this study was to examine racial differences in central BP in young African-American and white men.

A secondary purpose was to examine macrovascular and microvascular variables related to central hemodynamics.

Several methods were employed in an attempt to provide a comprehensive view of racial differences in vascular structure and function as it relates to central and peripheral hemodynamics.

Am J Physiol Heart Circ Physiol 295: H2380-H2387

doi:10.1152/ajpheart.00902.

Kevin S. Heffernan,¹ Sae Young Jae,^1,2 Kenneth R. Wilund,¹ Jeffrey A. Woods,¹ and Bo Fernhall¹

^{1The Exercise and Cardiovascular Research Laboratory, Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Champaign, Illinois; and 2Department of Sports Informatics, University of Seoul, Seoul, Korea}