Interrelationships among noninvasive measures of postischemic macro- and microvascular reactivity

Abstract

The clinical importance of vascular reactivity as an early marker of atherosclerosis has been well established, and a number of established and emerging techniques have been employed to provide measurements of peripheral vascular reactivity. However, relations between these methodologies are unclear as each technique evaluates different physiological aspects related to micro- and macrovascular reactive hyperemia. To address this question, a total of 40 apparently healthy normotensive adults, 19-68 yr old, underwent 5 min of forearm suprasystolic cuff-induced ischemia followed by postischemic measurements. Measurements of vascular reactivity included 1) flow-mediated dilatation (FMD), 2) changes in pulse wave velocity between the brachial and radial artery (DeltaPWV), 3) hyperemic shear stress, 4) reactive hyperemic flow, 5) reactive hyperemia index (RHI) assessed by fingertip arterial tonometry, 6) fingertip temperature rebound (TR), and 7) skin reactive hyperemia. FMD was significantly and positively associated with RHI (r=0.47) and TR (r=0.45) (both P<0.01) but not with reactive hyperemic flow or hyperemic shear stress. There was no correlation between two measures of macrovascular reactivity (FMD and DeltaPWV). Skin reactive hyperemia was significantly associated with RHI (r=0.55) and reactive hyperemic flow (r=0.35) (both P<0.05). There was a significant association between reactive hyperemia and RHI (r=0.30; P<0.05). In more than 75% of cases, vascular reactivity measures were not significantly associated. We concluded that associations among different measures of peripheral micro- and macrovascular reactivity were modest at best. These results suggest that different physiological mechanisms may be involved in changing different measures of vascular reactivity.

Endothelial dysfunction in cardiovascular disease and Flammer syndrome—similarities and differences

“…It comes to no surprise that in two large crosssectional cohort studies [44,45], non-invasive FMD of the brachial conduit artery and digital vascular dysfunction only modestly correlated and differed in their relation to traditional cardiovascular risk factors [46]. Thus, they might reflect different aspects of vascular biology [47].…”

“…In peripheral pneumatic arterial tonometry (PAT), digital pulse wave amplitude at baseline (preocclusion) and changes during reactive hyperemia are recorded and the reactive hyperemia-PAT index (RHI) is calculated as a standardized post-/preocclusion ratio [47,48]. RHI is correlated with coronary [49] endothelial dysfunction.…”

Impact of blood pressure cuff inflation rates on flow-mediated dilatation and contralateral arm response

“…24 Digital thermal monitoring Alterations in fingertip temperature in response to blood flow changes were assessed noninvasively by using the digital thermal monitoring technology (Vendys, Endothelix Inc., Houston, TX, USA) as previously described. 3 This system consists of a computer-based thermometry system, and two fingertip thermocouple probes. Fingertip skin temperature was measured by probes placed on the middle finger of both hands (occluded and non-occluded sides).…”

“…The increase in fingertip temperature above baseline temperature value after cuff deflation is the TR, which has been used as an index of vascular reactivity. 3 Neurovascular reactivity (NVR) was also obtained in the contralateral arm by calculating area under temperature curve during and after the occlusion. 16,17 Infrared thermography An infrared thermography camera (Ti45, Fluke Inc., Everett, WA, USA) was used to obtain images at baseline (1 min before occlusion), during occlusion (2 and 4 min), and deflation (immediately, 30 s, 60 s and 90 s) from both hands.…”

“…1,2 Assessment of reactive hyperaemia in macrovasculature and microvasculature following limb ischaemia provides early detection of impaired endothelial function. 3 Brachial flowmediated dilatation (FMD) is a widely used research tool and considered a biomarker of endothelial function. FMD has been associated with the presence of coronary artery disease.…”