How is single level disease identified through Reactive Hyperemia?

Single level disease is typically identified through Reactive Hyperemia by observing a 50% drop in ankle pressure. This response occurs when there is a transient occlusion of blood flow, which leads to a compensatory increase in flow once the occlusion is removed. In patients with single level disease, the area of stenosis causes a significant reduction in pressure upstream, leading to a measurable decline in ankle pressure during the reactive hyperemia test.

When blood flow is obstructed due to a single lesion, the body responds by attempting to increase blood supply to the affected region upon the release of that obstruction. The threshold for recognizing significant arterial disease is generally set at this 50% decline in ankle pressure, as it indicates that the downstream blood flow is compromised but may still be adequate in some respects.

In contrast, a 75% drop in ankle pressure might indicate more extensive disease or multiple levels of compromise. No drop in ankle pressure would be suggestive of an absence of significant arterial disease, while a continuous drop in pressure could signify the presence of severe disease or vascular insufficiency. Thus, a 50% drop serves as a critical benchmark in diagnosing single level stenosis effectively.