SESSION TITLE: Obstructive Sleep Apnea: Insights & Management SESSION TYPE: Original Investigation Slide PRESENTED ON: Sunday, October 29, 2017 at 01:30 PM - 03:00 PM PURPOSE: Endothelial dysfunction is an important phenomenon implicated in cardiovascular morbidity in obstructive sleep apnea (OSA) patients. While it has been demonstrated that continuous positive airway pressure (CPAP) therapy improves endothelial function, our understanding of the pathophysiologic links between CPAP therapy and cardiovascular outcomes remains limited. We further explored endothelial function in OSA patients before and after CPAP therapy. In addition, we studied relationship between endothelial function and aspirin responsiveness, as platelet hyperactivity has been suggested as another cardiovascular risk factor in OSA patients. METHODS: In this prospective cohort study, patients with newly diagnosed moderate-to-severe OSA (apnea-hypopnea index ≥ 15) underwent modified peripheral artery tonometry and platelet aggregometry before and after initiating CPAP therapy; the results were compared using paired samples t-test. Endothelial dysfunction was defined by a reactive hyperemia index (RHI) ≤ 1.67, and aspirin resistance as ≥ 550 ARU (aspirin reaction units). RESULTS: Of the 18 patients included in this study, 94% were male. The median age was 50 (32 to 64) years. At baseline, mean RHI was 1.79 (SD = 0.3); endothelial dysfunction was present in 8/18 patients (44%). After CPAP therapy (median length - 37 days), mean RHI increased to 1.94 (SD = 0.36), one-sided p = 0.015; endothelial dysfunction was found in 5/18 patients (28%). Most patients (14/18 or 78%) were classified as aspirin resistant at baseline. Among patients with endothelial dysfunction at baseline, CPAP therapy was associated with an increase in aspirin responsiveness that trended towards significance: mean ARU decreased from 563 (SD = 73) pre-CPAP to 520 (SD = 82) post-CPAP, one-sided p = 0.09. However, this trend was absent in patients with normal endothelial function: mean ARU decreased from 574 (SD = 80) to 566 (SD = 87), one-sided p = 0.4. CONCLUSIONS: CPAP therapy is associated with improvement in endothelial function in OSA patients. Larger studies are needed to confirm the correlation between CPAP therapy and improvement in aspirin responsiveness among patients with endothelial dysfunction, suggested by our results. CLINICAL IMPLICATIONS: Patients with untreated OSA have higher risk for cardivascular events. Majority of these patients are on aspirin therapy for primary or secondary prevention. Endothelial dysfunction and aspirin resistance may be prevalent among patients with OSA. CPAP therapy has potential to improve aspirin responsiveness in those patients that also have endothelial dysfunction. DISCLOSURE: The following authors have nothing to disclose: Lirim Krveshi, Oleg Sostin, Amber Butler, Cesar Artiles, Alan Sequieros, Joann Petrini, Jose Mendez No Product/Research Disclosure Information