HOME SUBSCRIPTIONS CURRENT ISSUE PAST ISSUES CARDIOSOURCE SEARCH HELP FEEDBACK		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Silber, H. A. Articles by Lima, J. A. C. Search for Related Content PubMed PubMed Citation Articles by Silber, H. A. Articles by Lima, J. A. C.

CLINICAL STUDY: ENDOTHELIAL FUNCTION

The relationship between vascular wall shear stress and flow-mediated dilation: endothelial function assessed by phase-contrast magnetic resonance angiography

^a Johns Hopkins Medical Institutions, Baltimore, Maryland, USA

Manuscript received October 23, 2000; revised manuscript received July 25, 2001, accepted August 20, 2001.

^* Reprint requests and correspondence: Dr. Joao A. C. Lima, Division of Cardiology, 568 Carnegie Building 410-614-1284, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, Maryland 21287 USA
jlima{at}mri.jhu.edu

OBJECTIVES

We sought: 1) to investigate the relationship between vascular wall shear stress and flow-mediated dilation (FMD) in humans, and 2) to investigate whether this relationship could explain why FMD is greater in small arteries.

BACKGROUND

Arterial wall shear stress (WSS) is considered to be the primary stimulus for the endothelial-dependent FMD response. However, the relationship between WSS and FMD has not been investigated in humans. Furthermore, FMD is greater in small arteries, though the reasons for this phenomenon are unclear.

METHODS

Using phase-contrast magnetic resonance angiography (PMRCA), we measured hyperemic WSS and FMD in 18 healthy volunteers. Peak systolic WSS was calculated assuming a blunted parabolic velocity profile. Diameter by PCMRA and by ultrasound was compared in nine subjects.

RESULTS

Flow-mediated dilation was linearly proportional to hyperemic peak systolic WSS (r = 0.79, p = 0.0001). Flow-mediated dilation was inversely related to baseline diameter (r = 0.62, p = 0.006), but the hyperemic peak WSS stimulus was also inversely related to baseline diameter (r = 0.47, p = 0.049). Phase-contrast magnetic resonance angiography and ultrasound diameters were compared in nine subjects and correlated well (r = 0.84, p < 0.0001), but diameter by PCMRA was greater (4.1 ± 0.7 mm vs. 3.7 ± 0.5 mm, p = 0.009).

CONCLUSIONS

Arterial FMD is linearly proportional to peak hyperemic WSS in normal subjects. Thus, the endothelial response is linearly proportional to the stimulus. Furthermore, the greater FMD response in small arteries is accounted for, at least partially, by a greater hyperemic WSS stimulus in small arteries. By allowing the calculation of vascular WSS, which is the stimulus for FMD, and by imaging a fixed arterial cross-section, thus reducing operator dependence, PCMRA enhances the assessment of vascular endothelial function.

Abbreviations and Acronyms   A = arterial cross-sectional area at peak systole   D = arterial lumen diameter at peak systole   FMD = flow-mediated dilation   MRI = magnetic resonance imaging   n = bluntness factor describing a paraboloid flow velocity profile, increasing n means a blunter profile   PCMRA = phase-contrast magnetic resonance angiography   VC = blood flow velocity in the center of the arterial cross-section during peak systolic flow   VSA = blood flow velocity, spatially averaged across the arterial cross-section at peak systole   WSR = wall shear rate at peak systole   WSS = wall shear stress at peak systole   µ = blood viscosity

This article has been cited by other articles:

				J. Schwitter Extending the Frontiers of Cardiac Magnetic Resonance Circulation, July 8, 2008; 118(2): 109 - 112. [Full Text] [PDF]

				S. Guthikonda, C. A. Sinkey, and W. G. Haynes What Is the Most Appropriate Methodology for Detection of Conduit Artery Endothelial Dysfunction? Arterioscler. Thromb. Vasc. Biol., May 1, 2007; 27(5): 1172 - 1176. [Abstract] [Full Text] [PDF]

				K. E. Pyke and M. E. Tschakovsky Peak vs. total reactive hyperemia: which determines the magnitude of flow-mediated dilation? J Appl Physiol, April 1, 2007; 102(4): 1510 - 1519. [Abstract] [Full Text] [PDF]

				H. A. Silber, J. A.C. Lima, D. A. Bluemke, B. C. Astor, S. N. Gupta, T. K. Foo, and P. Ouyang Arterial Reactivity in Lower Extremities Is Progressively Reduced as Cardiovascular Risk Factors Increase: Comparison With Upper Extremities Using Magnetic Resonance Imaging J. Am. Coll. Cardiol., March 6, 2007; 49(9): 939 - 945. [Abstract] [Full Text] [PDF]

				W. G. Hundley, E. Bayram, C. A. Hamilton, E. A. Hamilton, T. M. Morgan, S. N. Darty, K. P. Stewart, K. M. Link, D. M. Herrington, and D. W. Kitzman Leg flow-mediated arterial dilation in elderly patients with heart failure and normal left ventricular ejection fraction Am J Physiol Heart Circ Physiol, March 1, 2007; 292(3): H1427 - H1434. [Abstract] [Full Text] [PDF]

				B. A. Parker, S. J. Ridout, and D. N. Proctor Age and flow-mediated dilation: a comparison of dilatory responsiveness in the brachial and popliteal arteries Am J Physiol Heart Circ Physiol, December 1, 2006; 291(6): H3043 - H3049. [Abstract] [Full Text] [PDF]

				S. A. Wright, F. M. O'Prey, D. J. Rea, R. D. Plumb, A. J. Gamble, W. J. Leahey, A. B. Devine, R. C. McGivern, D. G. Johnston, M. B. Finch, et al. Microcirculatory Hemodynamics and Endothelial Dysfunction in Systemic Lupus Erythematosus Arterioscler. Thromb. Vasc. Biol., October 1, 2006; 26(10): 2281 - 2287. [Abstract] [Full Text] [PDF]

				D. Werner, P. Tragner, A. Wawer, H. Porst, W. G. Daniel, and P. Gross Enhanced external counterpulsation: a new technique to augment renal function in liver cirrhosis Nephrol. Dial. Transplant., May 1, 2005; 20(5): 920 - 926. [Abstract] [Full Text] [PDF]

				M. L. Bots, J. Westerink, T. J. Rabelink, and E. J.P. de Koning Assessment of flow-mediated vasodilatation (FMD) of the brachial artery: effects of technical aspects of the FMD measurement on the FMD response Eur. Heart J., February 2, 2005; 26(4): 363 - 368. [Abstract] [Full Text] [PDF]

				H. A. Silber, P. Ouyang, D. A. Bluemke, S. N. Gupta, T. K. Foo, and J. A. C. Lima Why is flow-mediated dilation dependent on arterial size? Assessment of the shear stimulus using phase-contrast magnetic resonance imaging Am J Physiol Heart Circ Physiol, February 1, 2005; 288(2): H822 - H828. [Abstract] [Full Text] [PDF]

				D. J. Pennell, U. P. Sechtem, C. B. Higgins, W. J. Manning, G. M. Pohost, F. E. Rademakers, A. C. van Rossum, L. J. Shaw, and E. K. Yucel Clinical indications for cardiovascular magnetic resonance (CMR): Consensus Panel report Eur. Heart J., November 1, 2004; 25(21): 1940 - 1965. [Full Text] [PDF]

				K. E. Pyke, E. M. Dwyer, and M. E. Tschakovsky Impact of controlling shear rate on flow-mediated dilation responses in the brachial artery of humans J Appl Physiol, August 1, 2004; 97(2): 499 - 508. [Abstract] [Full Text] [PDF]

				P. C. E. de Groot, F. Poelkens, M. Kooijman, and M. T. E. Hopman Preserved flow-mediated dilation in the inactive legs of spinal cord-injured individuals Am J Physiol Heart Circ Physiol, July 1, 2004; 287(1): H374 - H380. [Abstract] [Full Text] [PDF]

				L. Stoner, M. Sabatier, K. Edge, and K. McCully Relationship between blood velocity and conduit artery diameter and the effects of smoking on vascular responsiveness J Appl Physiol, June 1, 2004; 96(6): 2139 - 2145. [Abstract] [Full Text] [PDF]

				Y. H. Kao, E. R. Mohler, P. H. Arger, and C. M. Sehgal Brachial Artery: Measurement of Flow-mediated Dilatation with Cross-sectional US—Technical Validation Radiology, September 1, 2003; 228(3): 895 - 900. [Abstract] [Full Text] [PDF]

				A.-Y. Chong, A.D. Blann, and G.Y.H. Lip Assessment of endothelial damage and dysfunction: observations in relation to heart failure QJM, April 1, 2003; 96(4): 253 - 267. [Full Text] [PDF]