Patients with obstructive sleep apnea exhibit impaired endothelial function after myocardial infarction

Impaired brachial flow-mediated dilation (FMD) is associated with risk for subsequent cardiovascular events in patients after myocardial infarction (MI). These patients often have obstructive sleep apnea (OSA). We tested the hypothesis that patients with OSA post MI will exhibit more severe impairment in FMD.

We studied 64 patients with MI admitted to our hospital. OSA was determined using polysomnography. FMD was measured using high-resolution ultrasonography, with researchers blind to the OSA diagnosis.

The mean age was 60 ± 11 years, and the mean BMI was 29 (26, 32 kg/m(2)), 84% of patients were men, 39% had moderate to severe OSA (apnea-hypopnea index [AHI] > 15), and 31% of the patients had mild OSA (5 ≤ AHI < 15). FMD was severely impaired in patients with moderate to severe OSA (0.8% ± 0.7%) as compared with patients without OSA (4.7% ± 0.8%, P = .001) and with mild OSA (3.9% ± 0.8%, P = .015). Linear regression showed that FMD was associated with log nocturnal nadir oxygen saturation (minSaO(2)) (β = 31.17, P = .0001), age (β = -0.11, P = .006). MinSaO(2) was an independent predictor of FMD after adjustment for possible confounders (β = 26.15, P = .001).

FMD is severely impaired in patients with moderate to severe OSA post MI, which may be partially related to nocturnal hypoxemia. Patients with OSA may, therefore, be at higher risk for subsequent cardiovascular events after an MI. Identifying and treating OSA may have important implications in the long-term prognosis of patients post MI. Further studies are necessary to determine if the presence of OSA would affect the long-term occurrence of cardiovascular events after an MI.