The Effect of Acute Hypoxemia on Coronary Arterial Dimensions in Patients with Coronary Artery Disease

Abstract

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.

Ectatic Coronary Vasculopathy in Homocygous Alpha-1 Antitrypsin Deficiency

“…Alternatively, constant hypoxemia due to the patient´s lung disease might have caused aneurysm formation: Firstly, coronary dilation is regulated independent from the endothelium by arterial pressure, myocardial metabolism and the autonomic nervous system as well as by arterial oxygen-saturation [4]. Secondly, low blood oxygen saturation stimulates coronary vasodilatation in angiographically normal coronary arterial segments, whereas it does not affect vascular diameters in atherosclerotic segments [5]. In our patient, chronic hypoxemia might have boosted the rapid development of ectatic coronary angiopathy in a setting of increased proteolytic elastase-activity due to AAT deficiency.…”

The Effect of Hypoxia on Cardiovascular Disease: Friend or Foe?

“…In terms of coronary blood flow, hypoxia results in increased levels of coronary blood flow to accommodate the reduction in arterial O 2 content, although ultimate values in the chronic state can vary between the right and left coronary arteries and depend on both the supply side (restoration of arterial oxygen content from acclimatization) and the demand side (myocardial oxygen demands based on HR and ventricular loading conditions) (Moret et al, 1972;Grover et al, 1976). Coronary flow reserve is preserved in healthy individuals at altitude, but decreases in those with known coronary artery disease (CAD) during exercise (Wyss et al, 2003;Arbab-Zadeh et al, 2009).…”

Going High with Heart Disease: The Effect of High Altitude Exposure in Older Individuals and Patients with Coronary Artery Disease

“…Perhaps less well appreciated is the fact that atherosclerosis can lead to paradoxical vasoconstriction in the face of stresses like exercise (Gordon et al, 1989). Hypoxia may have similar effects (Arbab-Zadeh et al, 2009), particularly in the setting of marked sympathetic activation, thereby exacerbating the reduction in oxygen supply to the heart during hypoxic exposure. Figure 3 shows quantitative coronary angiograms from a patient with normal coronary anatomy demonstrating appropriate vasodilation in response to severe hypoxia; in contrast, a patient with coronary atherosclerosis demonstrates paradoxical vasoconstriction in response to the same degree of hypoxia.…”