Chest
Volume 127, Issue 1, January 2005, Pages 66-71
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Clinical Investigations: Sleep and Breathing
Accuracy of Monitoring for Sleep-Related Breathing Disorders in the Coronary Care Unit

https://doi.org/10.1378/chest.127.1.66Get rights and content

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.

Section snippets

Patients and Methods

Consecutive patients admitted to the Coronary Care Unit of Dunedin Hospital between April 1 and May 31, 2003, were invited to participate as soon as their clinical status had been satisfactorily stabilized. Inclusion criteria were as follows: diagnosis of unstable angina; acute MI; and left ventricular or congestive cardiac failure. Exclusion criteria were as follows: known diagnosis of OSA or other sleep-related disorder; or requiring ongoing supplementary oxygen therapy at the time of the

Results

There were 101 admissions to the CCU during the designated study period, of which 41 met the diagnostic criteria for inclusion in the study. Twelve patients declined to participate. Twenty-nine patients underwent the first sleep study (study 1), but complete data were available for only 26 patients. The remaining three patients were either intolerant of monitoring procedures2 or experienced chest pain during the study night.1 The final CCU admission diagnosis was MI in 14 patients (complicated

Discussion

The results of this observational study confirm that SDB is common in a highly selected group of at-risk patients who are admitted to the CCU. Using very conservative criteria for diagnosis, 12 patients (46%) were shown to have OSA and 1 had CSA at the time of their acute presentation. However, the results of the follow-up investigation showed that in a significant number of patients, the findings were transient and could not be repeated. A final diagnosis of SDB was confirmed in 5 of 26

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      The timing of the sleep diagnostic test could also be a concern since previous studies indicated that SDB is temporarily worsened in the acute phase after an MI and may be transient. However, some data suggest that the prevalence of SA shortly after an MI is the same as that recorded six months later [4,5,6]. In our study every subject underwent sleep monitoring at least 48 h after admission, and all were in stable condition.

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    The study was supported by the Otago Respiratory Research Trust and the Dunedin Heart Unit Trust.

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (e-mail: [email protected]).

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