What is the Origin of Reactive Hyperemia Index?

This clinical index originates from the field of vascular physiology and non-invasive cardiology, leveraging the body's natural homeostatic response to temporary blood flow occlusion. "Reactive Hyperemia" describes the transient, increased blood flow that occurs immediately after a period of ischemia, and "Index" refers to the standardized, calculated ratio of flow change. This diagnostic tool provides a functional window into the health of the systemic microvasculature.

What is the Mechanism of Reactive Hyperemia Index?

The measurement is based on the principle that temporary occlusion of arterial flow leads to the local accumulation of metabolic waste products and the release of potent endogenous vasodilators, primarily Nitric Oxide (NO) from healthy endothelial cells. Upon release of the occlusion cuff, the subsequent surge in blood flow (hyperemia) is directly proportional to the amount of NO released. A low index suggests impaired NO bioavailability and a reduced capacity for vasodilation, which are the fundamental hallmarks of early vascular disease.

Reactive Hyperemia Index

Meaning

The Reactive Hyperemia Index (RHI) is a non-invasive, quantitative diagnostic metric used to assess peripheral microvascular endothelial function, calculated from the change in digital blood flow following a brief, induced occlusion of blood supply. The index quantifies the magnitude of the maximal vasodilatory response (hyperemia) relative to the baseline flow. A lower RHI value is a robust indicator of endothelial dysfunction and serves as a significant, independent predictor of future cardiovascular events.

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Can You Measure Endothelial Function to Determine If Lifestyle Changes Are Sufficient for You?

Yes, measuring endothelial function provides an objective metric to determine if lifestyle changes have sufficiently improved vascular health.

∞ Nitric Oxide Synthase
∞ Nitric Oxide Production
∞ Endothelial Progenitor Cells

HRTioAugust 1, 2025

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Can Lifestyle Interventions Mitigate Anastrozole’s Vascular Effects?

Lifestyle interventions can mitigate Anastrozole's vascular effects by systematically supporting endothelial function through targeted diet and exercise.

∞ Endothelial Cells
∞ eNOS Activation
∞ Nitric Oxide

HRTioJuly 27, 2025