Study On Short-time Cardiovascular Time Series Analysis In Patients With Coronary Artery Disease

Coronary artery disease(CAD)has growing incidence rate and fatality rate year by year,shows the trend of younger,and brings aggressively harmful impact upon society and family.Early warning is a fundamental way to reduce the morbidity,mortality and disability rate of CAD.For this reason,it is of great significance to study the non-invasive and non-destructive identification of high-risk individuals with CAD.Nonlinear analysis of cardiovascular time series provides the possibility to solve the above problems.This dissertation aimed to investigate the potential value of non-invasive CAD detection using short-term(5 min)cardiovascular time series.For this purpose,three clinical trials were systematically designed and performed firstly.Then this dissertation investigated the univariate variability and bivariate coupling characteristics of cardiovascular time series in healthy volunteers,patients with mild coronary artery stenosis and CAD patients under the resting state and the state with changed peripheral vascular resistance,respectively.Finally,the nonlinear characteristics of cardiovascular time series in the recovery period after percutaneous coronary intervention(PCI)were studied.These studies provide a potential standardized method to identify high-risk individuals with CAD by short-term cardiovascular time series analysis.The main work and innovations includes the following aspects.(1)The development of the fuzzy entropy algorithm.Traditional fuzzy entropy neglects the influence of sampling errors and system disturbances.In this dissertation,a physical fuzzy membership function was defined,then a refined fuzzy entropy and a refined cross fuzzy entropy were developed.Simulation results indicated that the refined algorithms had significantly improved statistical stability and robustness against additive noise in comparison with the original fuzzy entropy and sample entropy.The statistical advantages of the improved algorithms are more obvious when the short time series is analyzed.(2)This dissertation investigated the changes of the univariate variability and bivariate coupling characteristics of cardiovascular time series in patients with coronary artery patients by expanding the scope of cardiovascular time series analysis,which reveals the changes of cardiac autonomic control and mechanic function in coronary artery stenosis.Results showed that the short-term heart rate variability(HRV),diastolic time interval variability(DTIV),heart rate-diastolic time interval(HRV-DTIV)coupling,heart rate-systolic time interval(HRV-STIV)coupling and diastolic time interval-systolic time interval(DTIV-STIV)coupling were significantly decreased(p<0.05 or p<0.01)in CAD patients,compared with healthy volunteers and patients with mild coronary artery stenosis.At the same time,diastolic time interval variability,heart rate-systolic time interval coupling and diastolic-systolic time interval coupling also declined significantly(p<0.05)in patients with mild coronary artery stenosis.Those results suggested the decline of cardiac autonomic control and mechanical function,as well as their interrelation induced by coronary artery stenosis.Furthermore,cardiac mechanical function might be more sensitive to coronary artery stenosis.(3)This dissertation had explored,for the first time,the effects of changed peripheral vascular resistance introduced by the external cuff inflation and deflation on heart rate variability,which should provide valuable tools for the non-destructive detection of coronary artery disease.The clinical trials showed that all the indices of heart rate variability in healthy elderly volunteers were lower than those of healthy young volunteers,but they both were hardly influenced by the external cuff inflation and deflation process(p>0.05).Nevertheless,the heart rate variability was significantly changed during the upper progress in both patients with mild coronary artery stenosis and CAD patients.It is suggested that coronary artery stenosis may decrease the adaptability of the cardiovascular system to the changes of external environment,and the heart rate variability analysis under the condition of cuff change of peripheral vascular resistance can further assist the non-destructive testing of coronary heart disease.(4)The dynamic changes of cardiovascular time series features in CAD patients after percutaneous coronary intervention were explored,which should provide potential valuable tools for intraoperative detection and prognosis analysis.Results showed that refined fuzzy entropy of heart rate variability and diastolic time interval variability had no significant changes on the first day after percutaneous coronary intervention,but they significantly increased on the 14th day after the operation.Besides,the coupling of heart rate-diastolic time interval,diastolic time interval-systolic time interval and heart rate-pulse transit time exhibited the same changes.Nevertheless,pulse transit time significantly increased short after the surgery.Those results indicated that the arterial elasticity and left ventricular function could have a quick improvement by successful percutaneous coronary intervention,while the improvement of autonomic nervous function needs a longer time.These findings further highlighted the value of cardiovascular time series analysis in evaluation of cardiovascular function after percutaneous coronary intervention.