Interindividual differences in the ischemic stimulus and other technical considerations when assessing reactive hyperemia

Reactive hyperemia is an established, noninvasive technique to assess microvascular function and a powerful predictor of all-cause and cardiovascular morbidity and mortality. Emerging evidence from our laboratory suggests a close link between reactive hyperemia and the metabolic rate of the ischemic...

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Published in:American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2019-10, Vol.317 (4), p.R530-R538
Main Authors: Rosenberry, Ryan, Trojacek, Darian, Chung, Susie, Cipher, Daisha J, Nelson, Michael D
Format: Article
Language:English
Subjects:
Adult
Aged
Aged, 80 and over
Aging
Average velocity
Cardiovascular diseases
Dependence
Desaturation
Female
Forearm
Geriatrics
Humans
Hyperemia
Hyperemia - physiopathology
Infrared spectra
Infrared spectroscopy
Ischemia
Ischemia - physiopathology
Male
Metabolic rate
Microvasculature
Morbidity
Near infrared radiation
Occlusion
Older people
Stimuli
Time Factors
Tissues
Ultrasound
Velocity
Young Adult
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Summary:Reactive hyperemia is an established, noninvasive technique to assess microvascular function and a powerful predictor of all-cause and cardiovascular morbidity and mortality. Emerging evidence from our laboratory suggests a close link between reactive hyperemia and the metabolic rate of the ischemic limb and the existence of large interindividual differences contributing to markedly different stimuli to vasodilate. Here we relate forearm tissue desaturation (i.e., the ischemic stimulus to vasodilate, measured by near-infrared spectroscopy) to brachial artery hyperemic velocity and flow (measured using duplex ultrasound) across a wide range of ischemic stimuli. Twelve young and 11 elderly individuals were prospectively studied. To recapitulate conventional vascular occlusion testing, reactive hyperemia was first assessed using a standard 5-min occlusion period. Then, to evaluate the dose dependence of tissue ischemia on reactive hyperemia, we randomly performed 4-, 6-, and 8-min cuff occlusions in both groups. In all cases, peak velocity, as well as the 5-s average velocity, immediately after the cuff occlusion was significantly higher in the young than the elderly group; however, tissue desaturation was also much more pronounced in the young group ( < 0.05), representing a greater ischemic stimulus. Remarkably, when reactive hyperemia was adjusted for the ischemic vasodilatory stimulus, group differences in reactive hyperemia were abrogated. Together, these data challenge conventional interpretations of reactive hyperemia and show that the ischemic stimulus to vasodilate varies across individuals and that the level of reactive hyperemia is often coupled to the magnitude of tissue desaturation.
ISSN:0363-6119
1522-1490
DOI:10.1152/AJPREGU.00157.2019