Accuracy of Monitoring for Sleep- Related Breathing Disorders in the Coronary Care Unit* Margot A. Skinner, MPhEd; Mahbubur S. Choudhury, MB ChB; Sean D.R. Homan, MSc; Jan O. Cowan, MB ChB; Gerard T. Wilkins, MB ChB; and D. Robin Taylor, MD Study objectives: To evaluate the frequency of sleep-disordered breathing (SDB) in patients presenting with acute cardiovascular events. Design: Repeat observational study. Setting: Coronary care unit of a university hospital. Patients: A total of 26 patients presenting with unstable angina, myocardial infarction, or left ventricular failure. Measurements: Level 3 portable sleep study performed at the time of acute presentation (study 1; 26 patients) and again > 6 weeks later (study 2; 18 patients). Results: SDB (apnea-hypopnea index > 15) was identified in 13 of 26 patients (50%) during study 1. One patient had central sleep apnea. Of the 18 who completed the two studies, SDB was confirmed in 10 of 18 patients (56%) during study 1 but in only 5 of 18 patients (28%) during study 2. All five of those patients had obstructive sleep apnea (OSA). Six patients were deemed to have false-positive results for SDB at follow-up, and one patient was deemed to have a false-negative result. Detailed analysis suggested that supine posture during study 1 may have contributed to the high false-positive rate, even though only three of six patients fulfilled the criteria for positional OSA. Conclusions: SDB occurs commonly in patients presenting with an acute cardiovascular event. Consideration of the diagnosis of SDB is an important strategy for secondary prevention. However, our findings indicate that SDB abnormalities may be transient. Sleep studies to investigate SDB as a potential risk factor for cardiovascular morbidity should be carried out when the patient is clinically stable. (CHEST 2005; 127:66 –71) Key words: cardiovascular risk; portable sleep monitoring; sleep apnea; sleep-disordered breathing Abbreviations: AHI = apnea-hypopnea index; CCU = coronary care unit; CSA = central sleep apnea; ESS = Epworth sleepiness scale; MI = myocardial infarction; OSA = obstructive sleep apnea; SDB = sleep-disordered breathing T he relationship between obstructive sleep apnea (OSA) and cardiovascular disease is complex. Epidemiologic evidence indicates that OSA is an independent risk factor for cardiovascular morbidi- ty. 1 The prevalence of hypertension is increased in subjects with OSA in a dose-dependent manner. 2–4 Similarly, the incidence of ischemic heart disease is increased with OSA, although the effect is more modest. 5 Conversely, OSA is more common in stable patients presenting with ischemic heart disease 6 and For editorial comment see page 4 acute myocardial infarction (MI). 7 More impor- tantly, long-term outcomes following MI are worse in those who have OSA. 7,8 For all of these reasons, making the diagnosis of OSA in patients with cardio- vascular disease is important, particularly given that adequate management improves the control of BP, 9,10 the prognosis for patients with congestive cardiac failure, 11,12 and the overall long-term mortal- ity rate. 13 In the acute clinical setting, there is a dynamic interaction between sleep-disordered breathing *From the Department of Medical and Surgical Sciences, Dun- edin School of Medicine, University of Otago, Dunedin, New Zealand. The study was supported by the Otago Respiratory Research Trust and the Dunedin Heart Unit Trust. Manuscript received March 11, 2004; revision accepted July 22, 2004. Reproduction of this article is prohibited without written permis- sion from the American College of Chest Physicians (e-mail: permissions@chestnet.org). Correspondence to: D. Robin Taylor, MD, Department of Medi- cine, Dunedin School of Medicine, PO Box 913, Dunedin, New Zealand; e-mail: robin.taylor@stonebow.otago.ac.nz 66 Clinical Investigations Downloaded From: http://journal.publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/22020/ on 06/27/2017