The effect of acute hypoxemia on coronary arterial dimensions in patients with coronary artery disease.

OBJECTIVES

To assess the influence of acute hypoxemia on the dimensions of diseased and nondiseased coronary arterial segments in humans.

METHODS

In 18 subjects (age 53 +/- 8 years) with known or suspected coronary artery disease, quantitative coronary angiography was performed before and after being randomly assigned to breathing (1) an inspired oxygen concentration (fraction of inspired oxygen, FIO2) of 21% (room air, RA) for 20 min (n = 4, controls) or (2) an FIO2 of 15 and 10% for 10 min each (corresponding to altitudes of 2,500 and 5,500 m, respectively; n = 14).

RESULTS

In the control subjects, no hemodynamic, oximetric or angiographic variable changed. In the 14 study subjects, the arterial partial pressure of oxygen averaged 85 +/- 13 mm Hg on RA, 65 +/- 15 mm Hg on 15% FIO2 and 44 +/- 13 mm Hg on 10% FIO2. Average arterial segment diameter was 2.52 +/- 0.63 mm on RA, 2.55 +/- 0.62 mm on 15% FIO2 (not significant vs. RA) and 2.66 +/- 0.66 mm on 10% FIO2 (p < 0.001 vs. RA). The increase in coronary arterial diameter with 10% FIO2 occurred only in normal segments (2.74 +/- 0.64 vs. 2.97 +/- 0.64 mm; p < 0.001), but not in diseased segments (2.34 +/- 0.57 vs. 2.38 +/- 0.55 mm; not significant).

CONCLUSIONS

In humans, severe hypoxemia induces vasodilation of angiographically normal coronary arterial segments, whereas it causes no change in diseased segments.