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Symptoms of Disturbed Sleep Predict Major Adverse Cardiac Events After Percutaneous Coronary Intervention
Study Questions:
What is the association between symptoms of disturbed sleep and adverse cardiovascular events after percutaneous coronary intervention (PCI)?
Methods:
This cross-sectional prospective cohort study was conducted at one tertiary hospital in Canada between August and November 2005. All patients in prearranged cardiology follow-up 1 month after PCI were assessed for symptoms of disturbed sleep with 10 questions. Patients were excluded if staged PCI were planned or if an adverse event was experienced between time of PCI and follow-up. Intermediate- and long-term follow-up were obtained by telephone between 7-10 months and at 4 years after PCI. The prespecified primary endpoint at long-term follow-up was a composite of death, myocardial infarction (MI), or need for repeat revascularization (PCI or bypass).
Results:
Of the 388 enrolled (total screened was not reported), 12 did not consent to follow-up and 38 could not be contacted, leaving 338 completing the study. The mean age was 66 ± 11 years. At baseline, 36 reported a diagnosis of sleep apnea and only 15 were compliant with positive airway therapy. The primary endpoint occurred in 89 patients (26%). In these patients, the average number of sleep symptoms was 3.8 ± 2.2 compared with 3.0 ± 2.0 for those in whom the primary endpoint did not occur (p = 0.001). Twenty-five patients had died on average 2.5 ± 1.3 years after the incident PCI. Patients with zero symptoms had a 4-year event rate of 12% compared with a 67% event rate for those with nine symptoms. On multivariable analysis, sleep symptoms, diabetes mellitus, and the number of diseased coronary vessels were independently associated with the primary endpoint. Each additional sleep symptom was associated with a hazard ratio (HR) of 1.2 (p = 0.001). The results were driven primarily by the association between symptoms of disturbed sleep and the need for repeated revascularization (repeated PCI hazard ratio, 1.9; p = 0.003; coronary artery bypass grafting hazard ratio, 1.5; p = 0.001).
Conclusions:
The authors concluded that symptoms of disturbed sleep were associated with increased risk of long-term adverse cardiovascular outcomes after successful PCI.
Perspective:
Although several mechanisms by which disturbed sleep can lead to adverse cardiac events have been proposed, there is yet a causal relationship. Endpoint data here are limited by accuracy of self reporting MI in follow-up. Additionally, disturbed sleep cannot be necessarily interchanged with sleep apnea or sleep disordered breathing. The questionnaire was not validated against polysomnography, which is considered the gold standard for diagnosing sleep disorders. Moreover, it is not clear how well questionnaires can predict cardiovascular events in a large population. Future studies may address whether interventions aimed at improving sleep can reduce cardiac events after PCI.
Keywords: Risk, Tertiary Care Centers, Myocardial Infarction, Follow-Up Studies, Cross-Sectional Studies, Sleep Wake Disorders, Canada, Angioplasty, Balloon, Coronary, Percutaneous Coronary Intervention, Polysomnography, Coronary Vessels, Coronary Artery Bypass, Diabetes Mellitus, Dyssomnias
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