Relationship between obstructive sleep apnea and coronary microcirculatory function among patients with cardiac syndrome X.

OBJECTIVES: Obstructive sleep apnea (OSA) is an emerging risk factor for cardiovascular disease. Microcirculatory dysfunction has been proposed as a potential mechanism in the pathogenesis of cardiovascular disease in OSA. This study aims to investigate the relationship between OSA and coronary microcirculatory function.

PATIENTS AND METHODS: One thousand and thirty-eight patients (598 female, mean age 60±9 years) with angiographically normal coronary arteries were divided into three groups with non-OSA of apnea-hypopnea index (AHI) less than 5 (n=403), mild-to-moderate OSA of AHI 5-30 (n=386), and severe OSA of AHI more than 30 (n=249).

RESULTS: The prevalence of OSA was very high in patients with syndrome X (635/1038). Patients with higher AHI values had a lower coronary flow reserve, were more likely to have a higher total cholesterol, low-density lipoprotein cholesterol, and high sensitive C-reactive protein, and were more likely to be obese. Compared with the non-OSA group, the multivariable-adjusted odds ratio of coronary microcirculatory function for an AHI of 5-30 events/h was 1.93, 95% confidence interval 1.66-3.47, P=0.038, and for an AHI of more than 30 events/h was 2.18, 95% confidence interval 1.62-4.23, P=0.024, in model 1; and coronary microcirculatory function for an AHI of 5-30 events/h and more than 30 events/h odds ratio 1.31, 95% confidence interval 1.06-2.88, P=0.043, versus odds ratio 2.08, 95% confidence interval 1.03-2.16, P=0.036, in model 2.

CONCLUSION: As compared with having no sleep apnea, categories with higher AHI were associated with increased odds of lower coronary flow reserve. The data suggested a close relationship between OSA and coronary microcirculatory function in atherosclerosis.