Impact of Obstructive Sleep Apnea on Outcomes in Acute Coronary Syndrome

Obstructive sleep apnea (OSA) is very common in middle aged adults. Using a polysomnography (PSG) derived definition, defined as an apnea hypopnea index (AHI) of >5, it occurs in 20-30 % of males and 10-15 % of females in North America. Various large epidemiological studies have established a close relationship between OSA and cardiovascular disease including coronary heart disease (CHD), heart failure, atrial fibrillation, and stroke. Potential mechanisms including endothelial dysfunction/ systemic inflammation, sympathetic activation, metabolic dysregulation, and mechanical load effects during respiratory events have been implicated for this relationship. However, in contrast to previous literature, more recent studies have also explored a cardio protective role of OSA. Repetitive hypoxemic episodes noted in OSA may lead to myocardial ischemic preconditioning, conferring protection in the form of a smaller myocardial infarct size, lower rates of cardiac arrhythmias, heart failure, and thereby, cardiovascular mortality. Animals exposed to intermittent hypoxia prior to ischemic insult experience significantly reduced infarct sizes when compared to animals not exposed to intermittent hypoxemia. Whether a similar effect exists in humans is still unclear. Recent research indicates better coronary collateral flow in OSA compared to control subjects presenting with acute coronary syndrome (ACS), which potentially could explain a cardioprotective role. Others have reported variable outcomes of coronary plaque burden and lesion complexity, restenosis and target vessel revascularization, serological markers such as troponin T, high sensitivity-C reactive protein (hs-CRP) and N-terminal pro brain natriuretic peptide (NT-proBNP), and major adverse cardiovascular events (MACE) in OSA vs. control subjects. Further, some of these early reports were limited by available devices, technology and methodology of the era. The objective of this study is to examine the prognostic role of OSA in patients with acute coronary syndrome (ACS). We tested the hypothesis whether OSA predicts subsequent MACE in patients undergoing percutaneous coronary intervention.

Methods This is a prospective, single center, observational study of patients presenting with ACS, including ST segment elevation (STEMI), non-ST segment elevation (NSTEMI) and unstable angina who undergo coronary revascularization at our tertiary care center. A total of 160 adult patients above age 18 years who meet our inclusion/ exclusion criteria will be enrolled. The estimated duration for this study is 2017-2018.

Prospective eligible patients who present for treatment for ACS at our institution in the study period will be approached for recruitment. Exclusion criteria for the study include: pregnancy, post-cardiac arrest patients, diagnosis of medical conditions associated with predicted survival of < 6 months, need for tracheostomy and prolonged mechanical ventilation, prior treatment for sleep disordered breathing and unavailable sleep data (due to death, no informed consent, uncooperative subject, technical difficulties, miscellaneous).

All subjects or their legally authorized representatives must provide written informed consent before any study-related procedure can be conducted. All recruited patients will undergo a level III sleep study within 48 to 72 hours prior to discharge. The patients will then be separated into OSA (AHI≥15 events/ h) and non-OSA (AHI<15) groups based on AHI.

There will be no financial incentive offered to patients. All recruited patients will be treated according to Declaration of Helsinki and amendments, World Medical Association Declaration of Helsinki - Ethical Principles for Medical Research Involving Human Subjects and standard clinical guidelines.