Key result
In response to increased blood flow, patients with normal coronary arteries showed a 23.2% dilation in cross-sectional area, whereas those with atherosclerosis showed a 7.4% constriction.
Why the study?
The study was motivated by the need to understand how large human coronary arteries respond to changes in blood flow and how this mechanism is altered in patients with atherosclerosis.
Does the presence of coronary atherosclerosis alter the endothelium-dependent vasomotor response of large coronary arteries to increased blood flow?
Observational (n=24)
Does the presence of coronary atherosclerosis alter the endothelium-dependent vasomotor response of large coronary arteries to increased blood flow?
Flow-mediated, endothelium-dependent vasodilation is intact in normal human coronary arteries but is lost in those with atherosclerosis, resulting in paradoxical vasoconstriction.
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
“Several studies, including the one by Nabel et al. (1) in this issue of the Journal, underscore a more dynamic paradigm to describe the behavior of healthy and diseased coronary arteries. In the study by Nabel et al. angiographically normal segments of mildly atherosclerotic coronary arteries failed to dilate as they should in response to increased blood flow induced by papavarine; moreover, the majority of vessels constricted paradoxically and inappropriately. The pathologic response of these mildly diseased arteries is probably due to endothelial cell dysfunction because acetylcholine (which induces endothelium-dependent relaxation) also failed to cause dilation in these patients, whereas nitrates (which cause smooth muscle relaxation) caused dilation.”
Flow-induced paradoxical constriction signals endothelial dysfunction in atherosclerosis; extends prior observations but leaves open prognostic value.
Changes in blood flow can alter vasomotion of conduit arteries. This study examined vasomotor responses to incremental blood flow induced by papaverine in the epicardial arteries of 10 patients with angiographically normal coronary arteries (group 1) and in 14 patients with arterial irregularities (group 2) using quantitative angiography and Doppler ultrasound flow velocity measurements. An increase in coronary blood flow of 384.3 +/- 32.8% (p less than 0.001) in group 1 patients was associated with dilation of the proximal coronary artery segment and a 23.2 +/- 4.6% increase in cross-sectional area (p less than 0.001). In contrast, in group 2 patients a similar increase in coronary blood flow of 339.3 +/- 18.7% (p less than 0.001) was associated with mixed responses and a modest net constriction in cross-sectional area of -7.4 +/- 2.8% (p less than 0.05). The dilation response to nitroglycerin was intact in group 1 (31.7 +/- 4.2%, p less than 0.001) and in group 2 (26.4 +/- 3.2%, p less than 0.001). In five patients from group 1 acetylcholine, an endothelium-dependent dilator, produced an increase in cross-sectional area of 20.7 +/- 4.6% (p less than 0.05) that paralleled the response to an increase in flow in the same segment (a 24.3 +/- 6.1% increase in cross-sectional area, p less than 0.05). Five group 2 patients demonstrated a vasoconstrictor response to acetylcholine (a -22.8 +/- 3.4% decrease in cross-sectional area, p less than 0.05) together with an impaired dilation response to incremental flow (a -6.4 +/- 3.2% decrease in cross-sectional area).(ABSTRACT TRUNCATED AT 250 WORDS)
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Nabel et al. (1990) conducted an observational in Atherosclerosis (n=24). Arterial irregularities (atherosclerosis) vs. Angiographically normal coronary arteries was evaluated on Change in cross-sectional area in response to increased blood flow. In response to increased blood flow, patients with normal coronary arteries showed a 23.2% dilation in cross-sectional area, whereas those with atherosclerosis showed a 7.4% constriction.
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