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Medicine

Non-invasive Assessment of Microvascular and Endothelial Function

Published: January 29th, 2013

DOI:

10.3791/50008

1Department of Family and Community Medicine, Thomas Jefferson University , 2Department of Pharmacology and Experimental Therapeutics, Biostatistics Division, Thomas Jefferson University, 3Department of Internal Medicine, Thomas Jefferson University

Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. The forearm blood flow technique provides accepted non-invasive measures of endothelial function.

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of cardiovascular disease. Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. Percent capillary recruitment is assessed by dividing the increase in capillary density induced by postocclusive reactive hyperemia (postocclusive reactive hyperemia capillary density minus baseline capillary density), by the maximal capillary density (observed during passive venous occlusion). Percent perfused capillaries represents the proportion of all capillaries present that are perfused (functionally active), and is calculated by dividing postocclusive reactive hyperemia capillary density by the maximal capillary density. Both percent capillary recruitment and percent perfused capillaries reflect the number of functional capillaries. The forearm blood flow (FBF) technique provides accepted non-invasive measures of endothelial function: The ratio FBFmax/FBFbase is computed as an estimate of vasodilation, by dividing the mean of the four FBFmax values by the mean of the four FBFbase values. Forearm vascular resistance at maximal vasodilation (FVRmax) is calculated as the mean arterial pressure (MAP) divided by FBFmax. Both the capillaroscopy and forearm techniques are readily acceptable to patients and can be learned quickly.

The microvascular and endothelial function measures obtained using the methodologies described in this paper may have future utility in clinical patient cardiovascular risk-reduction strategies. As we have published reports demonstrating that microvascular and endothelial dysfunction are found in initial stages of hypertension including prehypertension, microvascular and endothelial function measures may eventually aid in early identification, risk-stratification and prevention of end-stage vascular pathology, with its potentially fatal consequences.

Case Presentation (required, if applicable): N.A.; this is still an experimental research procedure, not yet used clinically.

Diagnosis, Assessment, and Plan (required, if applicable): N.A.; this is still an experimental research procedure, not yet used clinically.

Procedure (required): This part should include a step-by-step description of relevant procedures, meeting the guidelines below.

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Differences in the appearance of the microvasculature between normotensive and hypertensive individuals are readily apparent by comparing Figures 4 and 5. Figure 4 shows the typical network of straight capillaries in well organized rows in a normotensive individual. In contrast, Figure 5 demonstrates a more disarranged pattern of shrunken, coiled capillaries.

The authors have an ongoing interest in the role of microvascular dy.......

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Capillaroscopy (capillary microscopy) is a non-standard measure of capillary structure. However, currently, there are no standard methods for direct assessment of capillary structure.Furthermore, capillary microscopy has been widely used for the direct evaluation of capillarydensity in a large and growing body of published work 12, 13, 10, 11, 14-18. Additionally, we have validated the capillary microscopy technique by correlating capillaroscopy findings with forearm blood flow, a well-established measure of v.......

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This work was supported by Grant Award Numbers R01HL096593 and K23HL72825 from the National Heart, Lung, and Blood Institute. The content is solely the responsibility of Thomas Jefferson University and does not necessarily represent the official views of the National Heart, Lung, and Blood Institute or the National Institutes of Health.

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