How does the severity of coronary-artery stenosis affect basal and hyperemic myocardial blood flow in humans?
Hyperemic myocardial blood flow begins to decline at 40% coronary stenosis and is completely blunted (equal to basal flow) at 80% stenosis, establishing the physiological threshold for ischemia.
In humans, basal myocardial blood flow remains constant regardless of the severity of coronary-artery stenosis. However, during hyperemia, flow progressively decreases when the degree of stenosis is about 40 percent or more and does not differ significantly from basal flow when stenosis is 80 percent or greater.
Uren et al. (1994) studied this question.
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