心肌电兴奋传导速度对心律失常影响的仿真研究

心电场是由心肌的电活动产生的。心肌细胞的电特性及心肌细胞间的传导关系决定了体表电位的分布及心电图的变化。心肌电兴奋传导速度则是影响心肌间兴奋传导关系的重要参数之一。由于很难通过实验方法来人为改变电兴奋传导速度,因而临床上有关该参数对心律影响的定量知识相当缺乏。本文采用真实三雏躯干模型及心脏模型,对心肌电兴奋传导速度与心律变化的关系进行定量仿真研究。结果表明,兴奋传导速度决定了整个心电图的变化,而局部普通心肌的传导速度在相当范围内变化似乎对心电图影响不明显,但传导速度超过一定范围后可能产生突变。     

心率变异性信号的分析处理:现状与展望

一、概述 从1903年Einthoven第一次记录下人体的心电图至今已近一百年。这期间心电信号的分析处理取得了长足进展,已由对常规心电图的自动分析发展到体表多导心电图的描记及其逆向求解以及心电图中微小电位变化(如希氏束图、晚电位、高频变化等)的分析。近年来心率变异性Heart Rate Variability(HRV)成为心电信号处理中又一个前沿热点。 HRV是指连续心跳间瞬时心率的微小涨落或逐拍心跳R-R间期的微小涨落。人们发现,健康人的心率即使在静息状态下也非恒定不变,而是有起伏的。心率变异过小反而     

基于相关分析方法的非稳态心电T波交替检测研究

目的：研究T波段幅度、形态逐拍交替变化的心电变异现象检测。方法：本研究首先使用Mexican．hat小波检测R峰并对心电信号进行预处理;在提取T波矩阵方面为减少心拍间内差,采用点乘最大法,最大程度地对齐T波;最后基于时域相关分析方法检测T波交替幅度、交替心拍,追踪非稳态心电信号中短暂的交替数据段。结果：利用相关分析法对样本数据所测交替幅度与谱分析法相比更加显著,并且可以检测出谱分析方法无法检测的交替心拍。结论：时域相关分析方法能够更精确地追踪T波交替随时间变化的现象,但其对输入数据要求较高,因此在检测中可以先通过谱分析方法检测为阳性TWA的基础上,再对心电信号进行相关分析,从而确定非稳态交替时间段和更加准确的交替幅度。     

除草剂草甘膦异丙胺盐水剂对中华大蟾蜍心电活动的影响

采用生物信号采集处理系统对草甘膦异丙胺盐胁迫条件下中华大蟾蜍(BufogargarizansCantor)的心率和心电活动的相关指标进行了测定和分析。不同浓度的草甘膦异丙胺盐溶液被喷施到中华大蟾蜍的体表,由皮肤进入体内而作用于心脏。试验结果表明:随着草甘膦异丙胺盐处理浓度的增大,中华大蟾蜍的心率减慢,心电图中P波、R波和T波的电压峰值降低,而P-R间期、QRS期和Q-T间期的时值延长。草甘膦异丙胺盐胁迫条件下,蟾蜍心率与心电图的各项指标有显著相关性,可用多元线性回归模型分别对蟾蜍心率与心电图中P、R、T波和P-R、QRS、Q-T间期的相关关系进行拟合。多元回归分析结果表明,蟾蜍心电图中Q-T间期值对心率的影响最大,可以推断草甘膦异丙胺盐主要是通过延长蟾蜍心电活动周期中Q-T间期时值即心室收缩期而延长心动周期,导致蟾蜍心率减慢。由此可见草甘膦异丙胺盐水剂的喷施对中华大蟾蜍心脏的电活动周期和机械活动周期均造成了一定影响。     

心电数据压缩方法的新进展

一、引言 心电图(ECG)是心脏细胞电生理活动在体表的总体反应。1895年荷兰生理学家爱因妥芬(W.Einthoven)首次从体表记录到代表心脏完整的除、复极过程的心电波形,并以P、Q、R、S、T来标志不同的、可区分的波段,还给这类心脏电活动命名为心电图。从此开始了心电图的研究。并于在40、50年代建立了一套成熟的理论描述心脏活动的规律。     

替加色罗对内脏高敏感大鼠结肠电及运动的恢复

目的：探讨内脏高敏感大鼠结肠电活动和结肠运动的特点以及替加色罗治疗的疗效。方法：实验分对照组、模型组和替加色罗组,后两组腹腔注射鸡卵清蛋白使大鼠内脏致敏。记录结肠快波、慢波及收缩波,观察消化间期复合肌电及结肠收缩波数目、指数。结果：模型组消化间期复合肌电及结肠收缩波数目、指数均有明显变化。经替加色罗治疗后,各数据均有显著恢复。结论：内脏高敏感大鼠结肠电及运动有明显的异常,替加色罗治疗后能恢复被改变的电及运动。     

肾上腺素、乙酰胆碱对蟾蜍心电图的影响

本实验用肾上腺素和乙酰胆碱分别对蟾蜍的心电图变化进行了分析。实验同结果表明,注入肾上腺素和乙酰胆碱后出现明显的心电图各波段的变化,有的变化是相同的,提示这两种药物对蟾蜍心脏的电活动变化有一定的影响。     

P物质尾核微量注射抑制小鼠胃肌电活动和胃运动

本文观察了小鼠尾核微量注射Ｐ物质或乙酰胆碱对胃肌电和胃运动的ｍ影响;并初步探讨了两者作用的关系。用双极康铜导线引导胃窦部肌电;用水囊连接压力换能器记录胃窦部运动。上述信息经生物电放大器和载波放大器放大后,由四道记录仪描记曲线,同时输入微机进行采集、贮存和处理。计算出注药前后每分钟胃肌电快波、慢波和胃运动波的频率和总幅度的变化百分数。结果如下：尾核注射ＳＰ或ＡＣｈ胃电快波和胃运动呈明显的抑制效应。用     

心电图U波的临床意义综述

心电图Ｕ波的临床意义综述李玉冰广西中医学院一附院功能科５３００２３自１９２１年Ｅｍｔｈｏｕｅｎ描述心电图Ｕ波以来,Ｕ波近来越来越受到临床的重视,但对Ｕ波的正常形态、波幅大小和方向的变化,与临床疾病的内在联系,及Ｕ波产生的机理仍无统一认识,现综述如下。...     

封闭繁殖的成年东方田鼠心电图分析

记录并分析24例麻醉东方田鼠体表心电图。结果表明,（1）Ⅰ、Ⅱ、Ⅲ、aVF导联波形较稳定,主波向上,各波较明显;（2）aVR及部分aVL导联主波向下多见,QRS波群形态多样复杂;（3）各导联T波不对称,无明显S－T段,且不在等电位线上;（4）与大鼠相比各导联波幅值均低较,心率较快。     

TEMPERATURE CHARACTERISTIC FOR HEART BEAT FREQUENCY IN LIMAX

The temperature characteristic for the frequency of the heart beat in quiescent Limax maximus is µ = 16,300 calories. This value agrees well with that obtained for certain neurogenic activities of the parietal musculature of this gastropod.     

Spatiotemporal correlation analyses: a new procedure for standardisation of DC magnetocardiograms.

There is a lack of standard methods for the analysis of magnetocardiograms (MCGs). MCG signals have a shape similar to the ECG (P wave, QRS complex, T wave). High-quality multichannel recordings can indicate even slight disturbances of de- and repolarisation. The purpose of our study was to apply a new approach in the analysis of signal-averaged DC-MCGs. DC-MCGs (31-channel) were recorded in 182 subjects: 110 patients after myocardial infarction and 72 controls. Spatiotemporal correlation analysis of the QRS complex and T wave patterns throughout the entire heart cycle was used to analyse homogeneity of de- and repolarisation. These plots were compared to standard ECG analyses (electrical axis, Q wave, ST deviation, T polarity and shape). Spatiotemporal correlation analyses seem to be applicable in assessing the course of electrical repolarisation with respect to homogeneity. MCG provided all diagnostic information contained in common ECG recordings at high significance levels. The ECG patterns were included in 5/8 of our parameters for electrical axis, 6/8 for Q-wave, 7/8 for ST deviation and 5/8 for T-polarity based on two time series of correlation coefficients. We conclude that our spatiotemporal correlation approach provides a new tool for standardised analysis of cardiac mapping data such as MCG.     

Further studies on preservation of the beating rhythm of myocardial cells in culture

1. 1. Single myocardial cells from fetal mouse heart beat spontaneously in monolayer culture. In standard medium they maintained a constant beating rate for at least 5 h. After the beating rate of individual cells had been accelerated for a short time by electrical stimulation, the original beating rate could be immediately restored by interrupting the stimulation. Quiescent myocardial cells from neonatal mouse atrium could be induced to beat by electrical stimulation and most of them ceased to beat again immediately by interrupting the stimulation.

2. 2. After the spontaneous beating of individual myocardial cells had been stopped or slowed down for a short time by incubation in medium of low temperature or high potassium or low calcium concentration, the original beating rate could be restored by replacing the cells in the original, normal medium.

3. 3. After the spontaneous beating of individual myocardial cells had been stopped by adding a metabolic inhibitor, such as 2,4-dinitrophenol or 2-deoxyglucose, the original beating rate could be restored by replacing the cells in the original, normal medium.

4. 4. Both single myocardial cells and cell clusters showed arrhythmia, including flutter and fibrillation, in medium of low potassium or high calcium concentration. After a short period of arrhythmia, the original beating rate could be restored by replacing the cells in the original, normal medium. The arrhythmia of cell clusters produced in either low potassium or high calcium medium was also corrected immediately by addition of quinidine sulfate.

     

Machine Learning Approach to Detect Cardiac Arrhythmias in ECG Signals: A Survey

Cardiac arrhythmia is a condition when the heart rate is irregular either the beat is too slow or too fast. It occurs due to improper electrical impulses that coordinates the heart beats. Sudden cardiac death may occurs due to some dangerous arrhythmias conditions. Hence the main objective of the electrocardiogram (ECG) analysis is to detect the life-threatening arrhythmias accurately for appropriate treatment in order to save life. Since the last decades, several methods were reported for automatic ECG beat classifications. In this work, we present a systematic review of the current state-of-the-art methods used to detect cardiac arrhythmia using on ECG signals. It includes the signal decomposition, feature extraction and machine learning approaches used for automatic detection and decision making process. The articles covers the pre-processing, detection of QRS complex, feature extraction and classification of ECG beats. Based on the past studies, it is understood that the automated approach using computer-aided decision making process is highly required for real-time detection of cardiac arrhythmias. The advantages and limitations of different methods are discussed and also the future scopes is highlighted in the process of effective detection of cardiac arrhythmias. This study could be beneficial for researchers to analyze the existing state-of-art techniques used in detection of arrhythmia conditions.     

An interdisciplinary approach to certain fundamental issues in the fields of physics and biology: towards a unified theory

Recent experiments appear to have revealed the possibility of the existence of quantum entanglement between spatially separated human subjects. In addition, a similar condition might exist between basins containing human neurons adhering to printed circuit boards. In both instances, preliminary data indicates what appear to be non-local correlations between brain electrical activities in the case of the human subjects and also non-local correlations between neuronal basin electrical activities, implying entanglement at the macroscopic level. If the ongoing expanded research and the analysis of same continues to support this hypothesis, it may then make it possible to simultaneously address some of the fundamental problems facing us in both physics and biology through the adoption of an interdisciplinary empirical approach based on Bell's experimental philosophy, with the goal of unifying these two fields.     

THE RELATIONSHIP BETWEEN THE FINE STRUCTURE AND DIRECTION OF BEAT IN GILL CILIA OF A LAMELLIBRANCH MOLLUSC

This paper describes the fine structure and its relationship to the direction of beat in four types of cilia on the gill of the fresh-water mussel Anodonta cataracta. The cilia contain nine outer, nine secondary, and two central fibers, such as have been described previously in other material. Each outer fiber is a doublet with one subfiber bearing arms. One particular pair of outer fibers (numbers 5 and 6) are joined together by a bridge. The two central fibers are enclosed by a central sheath; also present in this region is a single, small mid-fiber. The different groups of fibers are connected together by radial links that extend from the outer to the secondary fibers, and from the secondary fibers to the central sheath. The basal body consists of a cylinder of nine triplet fibers. Projecting from it on one side is a dense conical structure called the basal foot. The cylinder of outer fibers continues from the basal body into the cilium, passing through a complex transitional region in which five distinct changes of structure occur at different levels. There are two sets of fibers associated with the basal bodies: a pair of striated rootlets that extends from each basal body down into the cell, and a system of fine tubular fibers that runs parallel to the cell surface. The relationship between fine structure and direction of beat is the same in all four types of cilia examined. The plane of beat is perpendicular to the plane of the central fibers, with the effective stroke toward the bridge between outer fibers 5 and 6, and toward the foot on the basal body.     

TEMPERATURE CHARACTERISTICS FOR HEART BEAT FREQUENCY IN MICE

An apparatus is described which permits the simultaneous recording of body temperature and heart beat frequency in young mice. When heart beat frequency is related to body temperature the values of the temperature characteristic for the inbred albino strain used are 22,400– calories over the range 15 to 20°+, 16,000± calories from 20+ to 27°, and 11,000± calories from 27 to 35°+.     

Automatic estimation of the correlation dimension for the analysis of electrocardiograms

The main purpose of the present work is the definition of a fully automatic procedure for correlation dimension (D₂) estimation. In the first part, the procedure for the estimation of the correlation dimension (D₂) is proposed and tested on various types of mathematical models: chaotic (Lorenz and Henon models), periodical (sinusoidal waves) and stochastic (Gaussian and uniform noise). In all cases, accurate D₂ estimates were obtained. The procedure can detect the presence of multiple scaling regions in the correlation integral function. The connection between the presence of multiple scaling regions and multiple dynamic activities cooperating in a system is investigated through the study of composite time series. In the second part of the paper, the proposed algorithm is applied to the study of cardiac electrical activity through the analysis of electrocardiographic signals (ECG) obtained from the commercially available MIT-BIH ECG arrhythmia database. Three groups of ECG signals have been considered: the ECGs of normal subjects and ECGs of subjects with atrial fibrillation and with premature ventricular contraction. D₂ estimates are computed on single ECG intervals (static analysis) of appropriate duration, striking a balance between stationarity requisites and accurate computation requirements. In addition, D₂ temporal variability is studied by analyzing consecutive intervals of ECG tracings (dynamic analysis). The procedure reveals the presence of multiple scaling regions in many ECG signals, and the D₂ temporal variability differs in the three ECG groups considered; it is greater in the case of atrial fibrillation than in normal sinus rhythms. This study points out the importance of considering both the static and dynamic D₂ analysis for a more complete study of the system under analysis. While the static analysis visualizes the underlying heart activity, dynamic D₂ analysis insights the time evolution of the underlying system. Received: 11 April 1997 / Accepted in revised form: 19 March 1999     

Electrophysiological control of ciliary motor responses in the ctenophorePleurobrachia

Prey capture by a tentacle of the ctenophore Pleurobrachia elicits a reversal of beat direction and increase in beat frequency of comb plates in rows adjacent to the catching tentacle (Tamm and Moss 1985). These ciliary motor responses were elicited in intact animals by repetitive electrical stimulation of a tentacle or the midsubtentacular body surface with a suction electrode. An isolated split-comb row preparation allowed stable intracellular recording from comb plate cells during electrically stimulated motor responses of the comb plates, which were imaged by high-speed video microscopy. During normal beating in the absence of electrical stimulation, comb plate cells showed no changes in the resting membrane potential, which was typically about -60 mV. Trains of electrical impulses (5/s, 5 ms duration, at 5-15 V) delivered by an extracellular suction electrode elicited summing facilitating synaptic potentials which gave rise to graded regenerative responses. High K+ artificial seawater caused progressive depolarization of the polster cells which led to volleys of action potentials. Current injection (depolarizing or release from hyperpolarizing current) also elicited regenerative responses; the rate of rise and the peak amplitude were graded with intensity of stimulus current beyond a threshold value of about -40 mV. Increasing levels of subthreshold depolarization were correlated with increasing rates of beating in the normal direction. Action potentials were accompanied by laydown (upward curvature of nonbeating plates), reversed beating at high frequency, and intermediate beat patterns. TEA increased the summed depolarization elicited by pulse train stimulation, as well as the size and duration of the action potentials. TEA-enhanced single action potentials evoked a sudden arrest, laydown and brief bout of reversed beating. Dual electrode impalements showed that cells in the same comb plate ridge experienced similar but not identical electrical activity, even though all of their cilia beat synchronously. The large number of cells making up a comb plate, their highly asymmetric shape, and their complex innervation and electrical characteristics present interesting features of bioelectric control not found in other cilia.     

A New Algorithm to Diagnose Atrial Ectopic Origin from Multi Lead ECG Systems - Insights from 3D Virtual Human Atria and Torso

Rapid atrial arrhythmias such as atrial fibrillation (AF) predispose to ventricular arrhythmias, sudden cardiac death and stroke. Identifying the origin of atrial ectopic activity from the electrocardiogram (ECG) can help to diagnose the early onset of AF in a cost-effective manner. The complex and rapid atrial electrical activity during AF makes it difficult to obtain detailed information on atrial activation using the standard 12-lead ECG alone. Compared to conventional 12-lead ECG, more detailed ECG lead configurations may provide further information about spatio-temporal dynamics of the body surface potential (BSP) during atrial excitation. We apply a recently developed 3D human atrial model to simulate electrical activity during normal sinus rhythm and ectopic pacing. The atrial model is placed into a newly developed torso model which considers the presence of the lungs, liver and spinal cord. A boundary element method is used to compute the BSP resulting from atrial excitation. Elements of the torso mesh corresponding to the locations of the placement of the electrodes in the standard 12-lead and a more detailed 64-lead ECG configuration were selected. The ectopic focal activity was simulated at various origins across all the different regions of the atria. Simulated BSP maps during normal atrial excitation (i.e. sinoatrial node excitation) were compared to those observed experimentally (obtained from the 64-lead ECG system), showing a strong agreement between the evolution in time of the simulated and experimental data in the P-wave morphology of the ECG and dipole evolution. An algorithm to obtain the location of the stimulus from a 64-lead ECG system was developed. The algorithm presented had a success rate of 93%, meaning that it correctly identified the origin of atrial focus in 75/80 simulations, and involved a general approach relevant to any multi-lead ECG system. This represents a significant improvement over previously developed algorithms.