Complex stenosis morphology and vasomotor responses to inhibition of nitric oxide synthesis

L-arginine preferentially dilates stenotic segments of coronary arteries thereby increasing coronary flow

BACKGROUND AND OBJECTIVES

Oxidized LDL cholesterol and cytokines increase arginase and decrease nitric oxide (NO) synthase expression in human endothelial cells, leading to a decrease in NO production. In arteriosclerotic plaques, characterized by increased oxidized LDL and cytokine levels, a sustained local NO reduction might enhance sensitivity of the downstream guanylyl cyclase system towards an acute NO increase. We tested whether application of the NO synthase substrate l-arginine (l-arg, 150 micromol min(-1)) or the NO donor isosorbide dinitrate (ISDN; 0.3 mg) preferentially dilates stenotic coronary artery segments (CS) subsequently increasing poststenotic coronary blood flow (CBF) in patients with coronary artery disease (CAD).

DESIGN, SETTING AND SUBJECTS

Changes in coronary diameter and circumferential surface area were assessed by quantitative coronary angiography (QCA) in a nonstenotic upstream segment, the CS, downstream the CS and in a reference vessel (n = 24). CBF was estimated in a subset of 13 patients by QCA and intracoronary Doppler.

RESULTS

CS ranged from 62% to 89% (77 +/- 5%). l-arg increased minimal luminal diameter of the stenotic segment from 0.98 +/- 0.06 to 1.14 +/- 0.07 mm (P < 0.05) without affecting other coronary segments. Poststenotic CBF increased by 24 +/- 3%. ISDN dilated all segments again with a predominance of CS (25 +/- 4%) and increased poststenotic CBF by 38 +/- 9%. In a multifactorial anova, a medication with an angiotensin-converting enzyme inhibitor (decreasing inflammation and radical formation) and a ratio of LDL/HDL <3.5 were predictive for an l-arg-induced dilation.

CONCLUSION

The increase in poststenotic CBF without affecting nondiseased arteries highlights the therapeutic potential of l-arg in patients with CAD.

Vasomotion and nitric oxide bioactivity in diseased coronary arteries

Atheromatous coronary stenoses are no longer considered to be passive structures, instead having the capacity for dynamic, often transient, change which may take the form of constriction or dilatation in response to either endogenous or external stimulation.

Vasomotor effects of L- and D-arginine in stenotic atheromatous coronary plaque

OBJECTIVE

To examine the effects of exogenous L- and D-arginine on coronary stenosis vasomotion in relation to stenosis morphology.

DESIGN

Intracoronary infusions of normal saline, L- and D-arginine (50 and 150 micromol/min), and glyceryl trinitrate (250 microg bolus) were given in 24 patients with coronary artery disease and stable angina. Coronary stenoses were classified as smooth or complex (irregular borders). The diameter of the coronary stenoses and their adjacent reference segments was measured by computed quantitative angiography.

RESULTS

During L-arginine infusion a larger proportion of complex stenoses than smooth stenoses dilated by >/= 10% (p < 0.01), and the magnitude of dilatation was greater at the site of complex stenoses (p < 0.05). Irrespective of the type of morphology there was a positive correlation (p < 0.01) between the severity of stenoses and the magnitude of vasodilatation to L-arginine. The response to glyceryl trinitrate was similar in the two groups. No significant change was found in either group in response to D-arginine.

CONCLUSIONS

In patients with coronary artery disease, coronary stenoses-particularly those of complex morphology-dilate in response to the administration of L-arginine but not D-arginine. This finding is consistent with partial deficiency of the substrate for nitric oxide synthesis, L-arginine, at the site of complex stenoses.