Sleep Quality Is Associated With Middle-term Prognosis Among Patients With Cardiac Syndrome X

Background:Cardiac syndrome X(CSX)is a clinical condition characterized by exertional angina,exercise induced myocardial ischemia,and normal coronary angiogram.A prior clinical study based on a small sample showed that the incidence of microvascular disease was about 45%?60%in patients with myocardial ischemia and nonobstructive coronary artery disease.Studies on the mechanism of CSX are mainly focused on coronary microvascular disease.Epidemiological studies find that traditional risk factors(hypertension,diabetes,smoking,etc.)and autonomic dysfunction are associated with the occurrence of CSX.Patients with CSX have fewer occurrence of major acute coronary events(cardiac death or acute myocardial infarction)than those with obstructive coronary artery disease at long-term follow up.However,they always have recurrent angina attacks and a significantly impaired quality of life because of recurrent medical visits,hospital admissions and coronary angiography,which could also increase the medicine costs and society burden.Nevertheless,we lack efficacious and practical screening tools to identify a population with worse prognosis.Sleep troubles are common complaints that can have a huge impact on folks' quality of life and ability to function.Short sleep duration and sleep disorders have emerged as being related to adverse cardiometabolic risk including obesity,hypertension,type 2 diabetes mellitus,and cardiovascular disease.The changes of autonomic nervous activity and the inhibition of respiratory regulation can lead to the changes of nervous,respiratory and hemodynamic systems,which are of great significance to the occurrence of cardiac events and cerebrovascular diseases.Sleep quality is a comprehensive evaluation of sleep duration and sleep quality.Clinical studies have found that sleep quality is closely related to metabolic syndrome and cardiovascular disease.It is not unreasonable to hypothesize that sleep quality might be associated with CSX.Objectives:This research is aimed to investigate the associations between sleep quality and middle-term clinical outcomes of CSX patients.Methods:All patients aged 18-75 referred for a clinically indicated diagnostic coronary angiography due to angina-like chest pain and suspected obstructive coronary artery disease(CAD)in Qilu Hospital of Shandong University between May 1,2012 and December 31,2015 were screened according to proposed definition of CSX.136 patients with CSX were included.Assessment included clinical data,lab tests.Pittsburgh Sleep Quality Index(scores greater than 5 indicate poor sleep quality)and TIMI Frame Count(TFC),which were then tested for prediction for clinical outcomes in a 4-year follow up(a median of 1.8 years).Results:62.5%patients reported poor sleep quality,female patients had a significant higher rate of poor sleep quality than male patients(73.3%and 44%,respectively).There was no statistically significant difference in age,BMI.resting heart rate,hypertension,diabetes,dyslipidemia,laboratory parameters,coronary blood flow and drug use between good sleep quality group and poor sleep quality group.However,participants with poor sleep quality were more likely to be female and patients without smoking history.During our follow up,no death or myocardial infarctions occurred and one participant had cerebral arterial thrombosis.26 patients were readmitted to the hospital at some stage of follow-up.The majority(66.9%)of our patients continued to have chest pain,of whom,2.2%developed worse symptoms with more frequent episodes or longer duration;19.1%suffered unchanged angina attacks.Patients with poor sleep quality had significantly lower probability of improvements in symptoms(disappeared or marked decreased angina attacks)when compared with those with good sleep quality.After elucidating the effects of traditional cardiovascular risk factors(age,diabetes,hypertension,and dyslipidemia),BMI and slow blood flow,poor sleep quality was associated with changes in angina symptoms(odds ratios 3.397;95%confidence interval 1.652-6.978;p=0.001).Cox proportional hazards model showed that poor sleep quality was an independent predictor of readmission(hazard ratio 3.094 95%confidence interval 1.161-8.245;p=0.024).Using the Kaplan-Meier survival analysis,patients with poor sleep quality were at an increased risk of readmission compared with patients with good sleep quality(p=0.033)Conclusion:Poor sleep quality is quite common among patients with CSX;female patients had a significant higher rate of poor sleep quality than male patients.Self-rated sleep quality was an independent predictor of changes in angina symptoms and readmission among CSX patients.As an economical,simple and practical screening method,sleep quality scale is of great significance for the detection of high-risk CSX patients.