Objective: Obstructive sleep apnea (OSA) has been associated with increased risk for cardiovascular events, possibly mediated by endothelial dysfunction. The current study evaluates the association between invasive coronary endothelial dysfunction and OSA in patients with nonobstructive coronary atherosclerosis.
Methods: All patients who had undergone both polysomnography and an invasive coronary vasomotor study at the Mayo Clinic, Rochester, Minnesota, from January 1997 to August 2011 were identified (n=143). OSA was defined as an apnea-hypopnea index of 5 or higher. Three endpoints of coronary endothelial function - percentage change in coronary artery diameter at the mid and distal left anterior descending artery to intracoronary acetylcholine and percentage change in coronary blood flow to intracoronary acetylcholine - were assessed. Differences between patients with OSA (n=102) and those without OSA (n=41) were evaluated using multivariate analysis of variance. Follow-up mortality data were collected and Kaplan-Meier curves were plotted to evaluate differences in mortality between patients with and without OSA.
Results: Patients with OSA were more likely to have hypertension compared with patients without OSA. OSA was not significantly associated with coronary endothelial dysfunction on univariate analysis (P=0.23) and after adjustment for hypertension (P=0.19). Similarly, there was no significant difference in coronary endothelial function in patients who had oxygen desaturation of less than 90% during polysomnography (P=0.42). There was a trend toward higher mortality in patients with OSA compared with those without OSA, but this did not reach statistical significance (5 vs. 0% at 10 years, P=0.25).
Conclusion: The current study suggests that OSA is not an independent risk factor for coronary endothelial dysfunction in patients with early coronary atherosclerosis. Adverse coronary outcomes in patients with OSA may be independent of coronary endothelial dysfunction.