Research On The Energy Analysis Of HCM Heart Sounds Signal In Time-Frequency Domain

The heart sound is a compound sound produced by the switch of the heart valve,the diastolic contraction of the tendons and muscles,the impact of the blood flow,and the vibration of the tube wall.In medical research,cardiovascular disease has always been a health killer that has plagued people all the time,heart sounds can reflect the state of the heart.The analysis of heart murmur before the patient has obvious clinical symptoms can provide important reference information for pathological diagnosis.So the heart sound is important for the clinical diagnosis of cardiovascular disease.Hypertrophic cardiomyopathy?HCM?is the current hot research trend in the world as a kind of cardiovascular disease.The research of HCM heart sound helps to a comprehensive understanding of cardiovascular disease.In the clinical,according to the left ventricle outflow tract gradient?LVOTG?value in resting state,HCM will be divided into hypertrophic obstructive type?LVOTG value ? 30 mm Hg?and hypertrophic non-obstructive type?LVOTG value?27?30mm Hg?.Hypertrophic non-obstructive type HCM can through the exercise experiment or drug inspire their hidden features.After excitation,some of them become hidden obstructive HCM?after exercise or drug stimulation,LVOTG value ? 30 mm Hg?,the other is still non-obstructive HCM?after exercise or drug stimulation,LVOTG value?27?30mm Hg?.In order to treat HCM in a better way,we should let the clinical diagnosis of non-obstructive HCM patients do exercise test in the medical.The prevention treatment of hidden obstructive HCM patients can help reduce the pain of patients,relieve the economic pressure and improve the cure rate.After comparing the energy characteristics in time-frequency domain of heart sound signals in normal,non-obstructive HCM and obstructive HCM patients,this article mainly analyzes the energy distribution characteristics in time-frequency domain of non-obstructive HCM?non-obstructive HCM after exercise test?and concealed obstructive HCM in resting,exercise,and recovery states.All of these are based on the pathological study of HCM in the Biomedical Information Research Laboratory.The severity of the disease will be judged by comparative analysis,which provide a reference for the clinical diagnosis.In order to accomplish the above objectives,this thesis will be researched from the following aspects:?1?The acquisition of clinical HCM heart sounds signalThe �digital auscultation device� has been used in the laboratory to collect the clinical HCM heart sounds signals,and the main acquisition parts are: Aortic?A?,Pulmonic?P?,Tricuspid?T?,Mitral?M?and Aortic₂?A2?,of which the heart sounds effect of Aortic₂?A2?is best.Based on the data of 30 normal people and 37 HCM patients,we applied 120 cases of normal heart sounds and 158 cases of heart sounds of HCM patients in this study.?2?Preprocessing of HCM heart sounds signalAffected by the noise in the actual acquisition process of clinical HCM heart sounds,the source of noise is analyzed first.And then conducts analysis of noise sources and analysis of mathematical modeling on HCM heart sounds acquired.Later,this paper applies three noise reduction algorithms,that is,wavelet filter,Kalman filtering and Wavelet based Kalman filter,to reduce the noise of clinical HCM heart sounds.The result of wavelet filter to preprocess noise reduction is the best after detailed comparing analysis.?3?Feature extraction of HCM signalIn order to facilitate the processing of data collected from the actual data,feature extraction is needed to be carried out after noise reduction preprocessing.In this research,the extraction effects of characteristic by four methods,that is,Hilbert transform?HT?,normalized average Shannon energy?NASE?,single degree of freedom model?SDOF?and frequency homomorphic filtering?FCHF?,have been discussed,and the results show that the effect by using frequency homomorphic filtering?FCHF?is the best.Time domain energy eight characteristic parameters of ES1?ESM1?ESM2?ESM3?ES2?EDM1?EDM2?EDM2 have been extracted.Two kinds of methods for frequency domain feature extraction have been discussed,namely,discrete fast Fourier transform?FFT?and normalized autoregressive power spectral density?NAR-PSD?.The frequency band range of HCM heart sounds is determined by NAR-PSD beause of NAR-PSD being more accurate.Frequency domain energy six characteristic parameters with wavelet coefficients of a5?d5?d4?d3?d2?d1 have been obtained.?4?Analysis of time-frequency domain energy characteristics of HCM heart soundsThis research analyzes the heart sounds signal energy characteristics in time-frequency domain of normal people,non-obstructive HCM patients and obstructive HCM?The severity of the disease increases successively?first.The energy distribution in patients with different conditions of HCM is preliminarily determined by energy distribution in time-frequency domain.And then this article mainly analyzes the energy distribution characteristics in time-frequency domain of non-obstructive HCM?non-obstructive HCM after exercise test?and hidden obstructive HCM in resting,exercise,and recovery states,non-obstructive HCM?non-obstructive HCM after exercise test?in resting,exercise,and recovery states,and hidden obstructive HCM in resting,exercise,and recovery states.According to mathematical statistics and analysis of extracted characteristic parameter values,we can find that energy distribution is consistent with the actual waveform distribution in time domain,and the more severe the condition,the wider the frequency distribution in frequency domain.This result can truly reflect the distribution of energy characteristic parameters in time-frequency domain,and provide a certain reference value for assisting judgment of disease condition.In this paper,we analyzed the heart sounds of HCM patients clinically acquired.The severity of the disease can be judged by analyzing the energy distribution characteristics of HCM heart sounds data under different types and states in time-frequency domain,which can truly reflect the distribution of HCM heart sounds,making HCM's auxiliary diagnosis has certain clinical reference value.