Model of reentrant ventricular tachycardia based on infarct border zone geometry predicts reentrant circuit features as determined by activation mapping

BACKGROUND: Infarct border zone (IBZ) geometry likely affects inducibility and characteristics of postinfarction reentrant ventricular tachycardia, but the connection has not been established. OBJECTIVE: The purpose of this study was to determine characteristics of postinfarction ventricular tachycardia in the IBZ. METHODS: A geometric model describing the relationship between IBZ geometry and wavefront propagation in reentrant circuits was developed. Based on the formulation, slow conduction and block were expected to coincide with areas where IBZ thickness (T) is minimal and the local spatial gradient in thickness (DeltaT) is maximal, so that the degree of wavefront curvature rho proportional, variant DeltaT/T is maximal. Regions of fastest conduction velocity were predicted to coincide with areas of minimum DeltaT. In seven arrhythmogenic postinfarction canine heart experiments, tachycardia was induced by programmed stimulation, and activation maps were constructed from multichannel recordings. IBZ thickness was measured in excised hearts from histologic analysis or magnetic resonance imaging. Reentrant circuit properties were predicted from IBZ geometry and compared with ventricular activation maps after tachycardia induction. RESULTS: Mean IBZ thickness was 231 +/- 140 microm at the reentry isthmus and 1440 +/- 770 microm in the outer pathway (P <0.001). Mean curvature rho was 1.63 +/- 0.45 mm(-1) at functional block line locations, 0.71 +/- 0.18 mm(-1) at isthmus entrance-exit points, and 0.33 +/- 0.13 mm(-1) in the outer reentrant circuit pathway. The mean conduction velocity about the circuit during reentrant tachycardia was 0.32 +/- 0.04 mm/ms at entrance-exit points, 0.42 +/- 0.13 mm/ms for the entire outer pathway, and 0.64 +/- 0.16 mm/ms at outer pathway regions with minimum DeltaT. Model sensitivity and specificity to detect isthmus location was 75.0% and 97.2%. CONCLUSIONS: Reentrant circuit features as determined by activation mapping can be predicted on the basis of IBZ geometrical relationships.     

Effect of resistive discontinuities on waveshape and velocity in a single cardiac fibre

A computer model of a one-dimensional cardiac fibre of resistively coupled cells is used to investigate the influence of the junction resistance on the nature of conduction. The results of the simulations are presented and indicate that the effect of the junction on both intracellular and extracellular waveshape and on the velocity of propagation depends on the size and frequency of the coupling resistance and the kinetics of the active membrane. Significant changes in these factors are not observed without the generation of prepotentials in the action potential upstroke. The absence of this ‘signature’ in microelectrode recordings of activity in ventricular muscle suggests that under normal conditions cardiac tissue behaves as a functional syncytium.     

Disturbance caused by varying propagation delay in non-occluding hearing aid fittings

The disturbance caused by various short propagation delays to the perception of external sounds and own voice for a non-occluding hearing aid was investigated. Ten normal-hearing and 10 mildly hearing-impaired individuals listened to external sounds and their own voice while wearing non-occluding devices providing 10dB of linear gain. Participants rated the disturbance caused by delays of 2, 4 and 10ms to music, running speech, and their own voices. The results indicated greater disturbance for the longest delay for both subject groups when judging own voice, with the ratings of the hearing-impaired participants being lowest. Normal-hearing participants also judged the 10-ms delay as more disturbing for the external sounds. Owing to the listening conditions with constant gain from 800Hz and above, the results apply directly only to this experiment. Disturbance ratings for all delays were low, which suggests that any of those tested would be acceptable for this application.     

基于机器学习的新型冠状病毒(COVID-19)疫情分析及预测

本研究采用数学建模的方式,在有限的数据下,通过机器学习对近期爆发的新型冠状病毒(COVID-19)肺炎确诊人数趋势进行了预测,根据有关部门发布的信息,预测了疫情拐点出现的时间,并对比了各省预计最终确诊人数所占的比例,以此为依据,大致划分了疫情的严重程度,对各省市人民防护工作有指导意义。     

三级公立医院微信公众平台建设与运营现状研究

调研分析厦门市12家三级公立医院微信公众平台基本情况、功能设置、信息发布与阅读情况以及微信传播指数,讨论其建设现状并提出相关建议,包括加强宣传、管理以及医院与用户的互动等。     

人-鼠抗CD4嵌合抗体的生物学效应研究

目的 探讨人－鼠抗ＣＤ４嵌合抗体的生物学效应,方法 观察ＣＤ４人－鼠嵌合抗体和鼠源性单抗对ＣＤ３,植物血凝素（ＰＨＡ）,白细胞－２（ＩＬ－２）及同种异体细胞诱导增殖的影响,以及介导的抗体依赖性细胞介导的细胞毒性（ＡＤＣＣ）作用。结果 提示ＣＤ４嵌合抗体和鼠源性ＣＤ４抗体对以上几种诱导剂诱导的增殖均有抑制作用,且抗体剂量越大,抑制作用越强。     

CD4细胞显微图像的分析与识别研究

介绍了CD4细胞的自动识别技术,利用图像处理技术实现了目标区域的分割,分析了形态、光密度、色彩、纹理四个方面的特征;采用主成分分析法提取特征,构建了BP网络分类器,较好的实现了CD4细胞的识别.     

Power spectra of single infinite fibre extracellular potentials recorded by a bipolar electrode

The power spectra of bipolarly recorded extracellular action potentials (EAPs) generated by an infinite, homogeneous, excitable fibre in an infinite, resistive, isotropic and homogeneous volume conductor were theoretically analysed. The changes in the power spectrum of EAP, which occurred as a result of alterations in the propagation velocity v and duration T_in of the intracellular action potential IAP, were analytically determined for bipolar parallel and radial electrodes with a small interpole distance. It was found that the sensitivity of the spectral characteristics to alteration in v, T_in and/or the IAP asymmetry substantially depends on the fibre-electrode distance; information on the IAP fast changes, that seems to be lost in unipolar recording as a result of the filtering effect of the fibre-electrode distance, can be restored. The orientation of the recording electrode need not be taken into account when a qualitative analysis is carried out, but when a quantitative analysis has to be performed, then the electrode orientation has a significant influence. A method is suggested for determination of the fibres' orientation by means of the spectrum of EAPs recorded bipolarly. The selectivity of the bipolar electrodes is analysed.     

猴痘病毒人类传播及其检测方法研究进展

猴痘是一种由猴痘病毒引起的人畜共患的新发病毒性疾病。1970年在非洲首次发现人感染猴痘病毒。2003年通过国境口岸将患病动物传入美国,并发生美国人类猴痘暴发流行。本文就近年来对猴痘病毒人间传播病例的回顾性研究及检测方法进展作一综述。     

Imaging onset and propagation of ECT-induced seizures

PURPOSE: Regions of seizure onset and propagation in human generalized tonic-clonic seizures are not well understood. Cerebral blood flow (CBF) measurements with single photon emission computed tomography (SPECT) during electroconvulsive therapy (ECT)-induced seizures provide a unique opportunity to investigate seizure onset and propagation under controlled conditions. METHODS: ECT stimulation induces a typical generalized tonic-clonic seizure, resembling spontaneous generalized seizures in both clinical and electroencephalogram (EEG) manifestations. Patients were divided into two groups based on timing of ictal (during seizure) SPECT tracer injections: 0 s after ECT stimulation (early group), and 30 s after ECT (late group). Statistical parametric mapping (SPM) was used to determine regions of significant CBF changes between ictal and interictal scans on a voxel-by-voxel basis. RESULTS: In the early injection group, we saw increases near the regions of the bitemporal stimulating electrodes as well as some thalamic and basal ganglia activation. With late injections, we observed increases mainly in the parietal and occipital lobes, regions that were quiescent 30 s prior. Significant decreases occurred only at the later injection time, and these were localized to the bilateral cingulate gyrus and left dorsolateral frontal cortex. CONCLUSIONS: Activations in distinct regions at the two time points, as well as sparing of intermediary brain structures, suggest that ECT-induced seizures propagate from the site of initiation to other specific brain regions. Further work will be needed to determine if this propagation occurs through cortical-cortical or cortico-thalamo-cortical networks. A better understanding of seizure propagation mechanisms may lead to improved treatments aimed at preventing seizure generalization.