利用Poincare散点图法检测t波交替的指标研究

A Study of Indexes of Poincare Scatter in the Detection of T-wave Alternans

目的:利用Poincare散点图进行t波交替检测,不仅从形态上找到检测标准,进一步研究散点中有效的定量指标。方法:以European ST-T Database标准心电数据库和MIT-BIH心律失常数据库的心电信号作为检测对象,以128个连续心拍的t波中的7个点为检测数据,相邻心拍t波差分后组成新序列,并由差分序列作出散点图,观察散点形态。根据形态区别和t波交替的幅值变化特点,利用个散点到x+y=0直线的距离均值作为定量检测指标D0,为避免不同心电信号幅值影响,D0除以RQ峰值差为最终指标D,找出合适阈值判定是否存在t波交替,并与谱分析法的检测结果比较分析。结果:①从Poincare散点图形态上,存在t波交替的散点图与正常t波存在明显区别,存在t波交替则散点集中在以x+y=0为轴线的附近,形成类似椭圆的狭长形状;而正常t波形成的散点会以原点为中心均匀分布,散点形态为圆形。②由t波交替的特点和散点图形态可知,定量检测指标D越小,就越有可能存在t波交替。经过大量仿真测试和谱分析法的比较,规定检测标准为,当D<=35uv时,存在t波交替;指标D与谱分析法的结论相吻合,并且两种方法的判定结果由kappa一致性检验,一致性程度好,进一步说明D指标具有优越的敏感性,是t波交替检测的有效指标。结论:Poincare散点图的散点分布形态和散点到x+y=0轴线的距离均值分别是是t波交替有效的定性和定量检测指标。

Objective： To research the effective indexes of Poincare scatter in the detection of T-wave alternans（TWA）,not only form the geometric pattern,but also from the quantitative index.Methods： Continuous 128 Beats electrocardiosignal（ECG） from MIT/BIH Arrhythmia database and European ECG ST-T database was read,and 7 sampling points from every t wave were selected to make a initial sample series.A new sequence with subtraction between adjacent beats of initial samples was used to draw a Poincare scatter.According to the different geometric patterns and the peculiarity of TWA,a new quantitative index was defined as D0 that was the mean distance from each point to the straight line x＋y=0.To avoid the influence made by amplitude from different ECG,the final index D was that D0 divided the difference between Q and R peaks.Then D was compared with the results of spectral method（SM）and appropriate threshold value was selected to recognize TWA.Results： ①The Poincare maps of ECG with TWA were greatly different from those of the normal.If there were TWA,the points mainly located in a long and narrow area which was near the straight line x＋y=0.While normal ECG would show us a evenly distributed round whit the origin as the center.② The likelihood of TWA existing increased with D value diminution.After abundant experiment,the standards were defined as follow： When mean distance D〈=35uv,there was TWA.A significant coherence was found between D the Stwa though kappa consistency test.Conclusion： Poincare scatter is a good method for the detection of TWA,and the geometric pattern and the mean distance D are effective qualitative and quantitative indexes.