Qualitative coronary flow evaluation of a pre-clinical percutaneous temporary aortic valve

Abstract

A published balloon-based percutaneous temporary aortic valve (TAV), with a specific fixed gap-to-aorta cross-sectional area ratio, was shown to provide haemodynamic support in acute aortic regurgitation (AR). The fixed gap of the balloon-TAV, however, limits the ability to optimize the gap size balancing coronary flow vs AR protection. Hence, a reduced diastolic gap may improve AR protection, but could reduce coronary flow and increase systolic TAV flow resistance. A new membrane-based TAV, which avoids these design limitations, could guide gap size optimization and advance the development into a pre-clinical tool. The re-designed TAV prototype has a membrane-cone collapsible in systole to reduce flow resistance and expands in diastole with a gap-to-aorta cross-sectional area ratio that can be tailored to optimize AR protection and coronary flow. Without the concern for systolic TAV flow resistance, a lower limit of the gap:aorta cross-sectional area ratio could be determined. The ability of the membrane-TAV design in determining an optimal gap:aorta ratio is tested in an in vitro flow chamber. Three prototypes with reducing gap:aorta cross-sectional area ratios (35%, 15%, 0%) were tested in a flow chamber of simulated acute severe AR. Correspondingly, increasing in forward cardiac output volumes, coronary flow:aortic regurgitant volume ratios and reduction in aortic regurgitant volumes were observed (p?<?0.001) in the three models. The membrane-TAV concept contains a design feature for optimization of LV protection from acute AR and coronary perfusion by defining an optimal gap:aorta ratio. Along with the results from the balloon-TAV, a clinically useful percutaneous device for the management of acute severe aortic regurgitation is becoming possible.     

基于小波包变换的癫痫脑电棘波检测

为了能够较好地实现癫痫患者脑电的棘波检测,提出一种将棘波物理特征（幅度、频率）和小波包变换结合的算法,用于癫痫患者脑电信号的棘波检测。首先利用小波包变换对癫痫脑电信号进行小波包分解,将脑电波频率（0~30 Hz）划分为3层;其次根据脑电波的频率范围重构第三层节点频率S（3, 0）（0~10.85 Hz）、S（3, 1）（10.85~21.7 Hz）、S（3, 2）（21.7~32.55 Hz）的脑电信号;最后取棘波的幅度作为检测阈值分别提取癫痫患者健康期、癫痫发作间期及癫痫发作期的棘波。实验结果证明,当数据的采样频率为173.61 Hz、信号长度为23.6 s时,该算法能够提取不同癫痫患者在不同时期的棘波信号,该算法棘波的误检率为12.02%、漏检率为11.70%。因此,本文所采用的算法在癫痫棘波检测中具有良好的效果。     

基于小波系数熵的表面肌电信号识别

目的:对表面肌电信号进行分类识别。方法:30名健康的志愿者参加数据采集。每名志愿者用右手臂完成两个动作:前臂内旋和前臂外旋。在每个动作中,采集一组表面EMG信号。总共获得30组内旋和30组外旋的表面EMG信号。然后,运用小波包系数熵构成特征向量,用Bayes决策对两种模式信号进行分类识别。结果:当信号长度达350ms后,正确识别率达到100%。结论:采用小波包系数熵可以有效地提取表面EMG信号的特征信息,达到控制前臂假肢的目的。     

Estimation of arterial compliance in aortic regurgitation: three methods evaluated in pigs

Three methods for measuring arterial compliance when aortic regurgitation is present are examined. The first two methods are based on a Windkessel model composed of two elements, compliance C and resistance R. Arterial compliance was estimated from diastolic pressure waveforms and diastolic regurgitant flow for one method, and from systolic aortic pressure waveforms and systolic flow for the other method. The third method was based on a three-element Windkessel model, composed of characteristic resistance r, compliance C and resistance R. In this method arterial compliance was calculated by adjusting the model to the modulus and phase of the first harmonic term of the aortic input impedance. The three methods were compared and validated in six anaesthetised pigs over a broad range of aortic pressures. The three methods were found to give quantitatively similar estimates of arterial compliance at mean aortic pressures above 60 mm Hg. Below 60 mm Hg, estimates of arterial compliance varied widely, probably because of poor validity of the Windkessel models in the low pressure range.     

Analog simulation of aortic and of mitral regurgitation

By using an equivalent electronic circuit either mitral or aortic regurgitation was simulated. Simulation allowed not only a measurement of various pressures within the cardiovascular system and cardiac output, but also mitral and aortic flow.In normal conditions mitral and aortic flows were monophasic, anterograde. In valve regurgitation mitral and aortic flows were, as expected, biphasic.In mitral regurgitation, during systole and diastole the valve flow was retrograde and anterograde, respectively.In aortic regurgitation, during systole and diastole the valve flow was anterograde and retrograde, respectively.The magnitude of the regurgitant valve flow was measured by time-integration and compared to the net flow, i.e. cardiac output. Valve flow was determined not only by the magnitude of valve dysfunction, but also by the resistive/capacitive characteristics of the “falsely” attached regurgitant circuit. If the regurgitant valve flow was large enough, it in turn affected the function of the left ventricle.The present investigation suggests that many features observed in patients with mitral or aortic regurgitation can be qualitatively satisfactorily simulated. In some respects even quantitative simulation is possible. However, for simulation of chronic mitral or aortic regurgitation, in the analog electronic circuit additional adjustments—in capacitance of the left ventricle and pulmonary system—would be required.     

不同钙化模式对经导管主动脉瓣膜植入效果影响的数值模拟研究

目的通过有限元方法评估不同钙化模式对经导管主动脉瓣膜植入效果的影响。方法根据钙化斑块在主动脉瓣叶上的位置不同,建立对合线钙化模型、附着线钙化模型和圆圈钙化模型3种不同钙化形式的主动脉根部模型。使用ABAQUS软件仿真自膨胀经导管主动脉瓣膜植入3个钙化模型中的过程,分析不同钙化模型对主动脉根部应力、瓣架变形以及瓣周间隙的影响。结果圆圈钙化模型中钙化斑块的最大主应力最大,为18.42 MPa,可能导致假体植入后发生脑卒中的风险更高;圆圈钙化模型的瓣架变形程度也最大,可能导致更差的假体耐久性;附着线钙化模型的瓣周间隙面积为37.2 mm~2,超过其他模型的2倍,植入后出现严重瓣周返流的风险可能性更高。结论不同的主动脉瓣叶钙化模式与经导管主动脉瓣膜植入后的主动脉根部应力、瓣架变形以及瓣周间隙有关,对术后并发症和假体耐久性产生影响。研究结果为临床上经导管主动脉瓣膜植入术术后效果的预测提供参考。     

ECG beat classification using empirical mode decomposition and mixture of features

Computer-aided analysis is useful in predicting arrhythmia conditions of the heart by analysing the recorded ECG signals. In this work, we proposed a method to detect, extract informative features to classify six types of heartbeat of ECG signals obtained from the MIT-BIH Arrhythmia database. The powerful discrete wavelet transform (DWT) is used to eliminate different sources of noises. Empirical mode decomposition (EMD) with adaptive thresholding has been used to detect precise R-peaks and QRS complex. The significant features consists of temporal, morphological and statistical were extracted from the processed ECG signals and combined to form a set of features. This feature set is classified with probabilistic neural network (PNN) and radial basis function neural network (RBF-NN) to recognise the arrhythmia beats. The process achieved better result with sensitivity of 99.96%, and positive predictivity of 99.81 with error rate of 0.23% in detecting the QRS complex. In class-oriented scheme, the arrhythmia conditions are classified with accuracy of 99.54%, 99.89% using PNN and RBF-NN classifier respectively. The obtained result confirms the superiority of the proposed scheme compared to other published results cited in literature.     

David手术在主动脉根部瘤合并主动脉瓣二叶畸形治疗中的应用

目的 探讨David手术在治疗主动脉根部瘤合并主动脉瓣二叶畸形中应用的临床效果。方法 回顾性研究。纳入南京大学医学院附属鼓楼医院心胸外科2016年1月—2019年1月行David手术治疗主动脉根部瘤合并主动脉瓣二叶畸形的11例患者临床资料。其中男8例、女3例,年龄18～60(35±13)岁;主动脉瓣轻度反流7例、轻中度反流4例,心功能Ⅱ级5例、Ⅲ级5例、Ⅳ级1例。观察患者围术期指标;术后定期复查心脏超声,观察人工血管通畅情况及主动脉瓣反流情况,包括左室射血分数、主动脉瓣反流程度、平均跨瓣压差、峰值跨瓣压差及最大血流速度。结果 11例患者均成功实施手术。围术期观察指标:体外循环时间(246.1±27.2)min,主动脉阻断时间(207.5±21.5)min,术后机械通气时间4.5(3.25,9.25)h,重症监护时间(2.8±1.5)d,术后24 h引流量(418.2±299.0)mL。所有患者术后随访18~30个月,平均22.5个月,未见死亡及二次手术病例。随访期间心脏超声显示患者人工血管血流均通畅,主动脉瓣轻微反流8例、轻度反流3例,平均跨瓣压差均＜10 mmHg(1 mmHg=0.133 kPa),末次随访时,患者心功能Ⅰ级8例、Ⅱ级3例,较术前明显改善。结论 采用David手术结合主动脉瓣修复技术治疗主动脉根部瘤合并中度以下反流的主动脉瓣二叶畸形,其临床疗效满意。     

经心尖主动脉瓣置换术治疗高危单纯无钙化主动脉瓣关闭不全的手术配合

目的探讨国产J-Valve?支架瓣膜行经心尖主动脉瓣置换(TAVR)术治疗高危单纯无钙化主动脉瓣关闭不全的手术配合方法。 方法收集2017年3月至2018年3月在首都医科大学附属北京安贞医院高危单纯无钙化主动脉瓣关闭不全患者资料,共15例。所有患者均使用国产J-Valve?系统为患者行TAVR术。经过细致的术前评估(包括术前访视、熟悉仪器设备、介入耗材设备等)、术中流畅的手术配合[包括严格遵循无菌原则、术中患者体温保护、X线防护、激活全血凝固时间(ACT)的监测以及支架瓣膜的装配等]和术中安全管理(包括防止输送器移位和动脉置管的护理等)。观测患者术中是否使用心肺转流、发生心室快速起搏、中转行常规体外循环下TAVR术,是否有冠状动脉阻塞、植入瓣膜是否有移位,有无瓣膜内狭窄及瓣周漏等情况发生,观测术后即刻平均主动脉瓣跨瓣压差;患者在ICU是否顺利脱离呼吸机拔除气管插管,术中平均出血量、患者在ICU时间和呼吸机辅助通气时间、射血分数以及是否存在瓣周漏等;了解患者心功能分级、活动耐量以及是否存在胸闷、心绞痛等症状。 结果本研究中所有患者均成功完成TAVR术,未使用心肺转流、未发生心室快速起搏,无中转行常规体外循环下TAVR术,未发生冠状动脉阻塞或植入瓣膜移位,未见瓣膜内狭窄及瓣周漏等情况。术后即刻平均主动脉跨瓣压差为[5.8(4.9,12.9)] mmHg(1 mmHg＝0.133 kPa)。所有患者在ICU均顺利脱离呼吸机拔除气管插管,术中平均出血量为[200.0 (100.0, 500.0)]mL,患者在ICU时间为(1.2±0.4) d,呼吸机辅助通气时间为[19.0 (8.5, 23.5)] h,平均射血分数为(56.2±15.6)%,仅有2例患者存在微量瓣周漏。末次随访中,10例患者心功能Ⅰ级,4例为Ⅱ级,1例为Ⅲ级;患者的活动耐量都较术前明显改善;患者术后胸闷、心绞痛等症状较术前明显改善。 结论手术室护士正确掌握TAVR术的手术配合方法,术前做好患者的心理护理以及各项术前准备,手术过程中与外科医师密切配合,是患者手术成功的保证。     

Partial aortic root remodeling for root reconstruction in patients with acute type A dissection

In the present study, we reported our experience with partial aortic root remodeling for root reconstruction in patients with acute type A dissection, which involves in non-coronary sinus and/or the right coronary sinus with just one trimmed Dacron graft. Between February 2001 and May 2010, we performed partial aortic root remode-ling in 40 patients, who underwent emergency surgical intervention. The dissected sinuses were excised leaving a 3-5 mm rim of the aortic wall from the attached aortic valve cusps. A short piece (4-5 cm) of collagen coated woven polyester vascular prosthesis was trimmed with one or two "tongues" to reconstruct the non-coronary sinus and/ or the right coronary sinus, but without using separated patches. Additional procedures were including hemi-arch replacement in 11 patients, and total arch replacement plus stent-elephant trunk in 20 patients. The mean follow-up time was 36.4±3.6 months. In-hospital mortality was only 5.0% (2/40); furthermore, 3 (8.6%) patients underwent re-operation of the aortic valve and 2 (5.7%) patients died during follow-up. At the end of follow-up, trivial or no aortic regurgitation was found in 33 patients, but mild aortic regurgitation was found in 2 patients. Our data suggest that the early and mid-term results of partial aortic root remodeling were favorable, and it restored valve durability and function. Thus, the use of technique for root reconstruction in patients with acute type A dissection should be vigorously encouraged.     

Computational simulations of mitral regurgitation quantification using the flow convergence method: Comparison of hemispheric and hemielliptic formulae

Mitral regurgitation results from the incomplete closure of the mitral valve, and the noninvasive diagnosis of this disease remains an important clinical goal. In this study, steady flow computer simulations were used to evaluate flow convergence method for flow rate estimation. The hemispheric and hemielliptic formulae were compared for accuracy in the presence of complicating factors such, as ventricular confinement, orifice shape, and aortic outflow. Results showed that in the absence of aortic outflow and ventricular confinement, there was a plateau zone where the hemispheric formula approximated the true flow rate, independent of orifice shape. However, in the presence of complicating factors such as aortic outflow and ventricular confinement, there was no clear zone where the hemispheric formula could be applied. The hemielliptic formula, however, worked in, all cases, regardless of chamber size or magnitude of aortic outflow. Therefore, application of the hemielliptic formula shold be considered in future clinical studies.     

Different approaches for identifying important concepts in probabilistic biomedical text summarization

Automatic text summarization tools help users in the biomedical domain to acquire their intended information from various textual resources more efficiently. Some of biomedical text summarization systems put the basis of their sentence selection approach on the frequency of concepts extracted from the input text. However, it seems that exploring other measures rather than the raw frequency for identifying valuable contents within an input document, or considering correlations existing between concepts, may be more useful for this type of summarization. In this paper, we describe a Bayesian summarization method for biomedical text documents. The Bayesian summarizer initially maps the input text to the Unified Medical Language System (UMLS) concepts; then it selects the important ones to be used as classification features. We introduce six different feature selection approaches to identify the most important concepts of the text and select the most informative contents according to the distribution of these concepts. We show that with the use of an appropriate feature selection approach, the Bayesian summarizer can improve the performance of biomedical summarization. Using the Recall-Oriented Understudy for Gisting Evaluation (ROUGE) toolkit, we perform extensive evaluations on a corpus of scientific papers in the biomedical domain. The results show that when the Bayesian summarizer utilizes the feature selection methods that do not use the raw frequency, it can outperform the biomedical summarizers that rely on the frequency of concepts, domain-independent and baseline methods.     

基于功率谱信息熵的异常心音识别

目的：异常心音识别是心血管疾病检测的一种重要手段,为了探究异常心音频域的有用信息,提出了将不同频段的功率谱作为一个独立信源计算其信息熵,从而对房室瓣和动脉瓣异常信号进行判别的一种新方法。方法：实验先将心音信号进行小波包分解,然后利用改进的Welch方法计算信号的功率谱,进而求各频段的功率谱信息熵,再建立支持向量机预测模型来对两种异常心音进行识别。结果：选取二尖瓣狭窄、二尖瓣关闭不全、主动脉瓣狭窄、主动脉瓣关闭不全共27例心音信号进行算法仿真,其中房室瓣异常能够全部检测出来,动脉异常有3例被误判,正确率达到77％;在原有27例信号的基础上,增加3例房室瓣异常和3例动脉异常信号进行算法验证,房室瓣异常信号仍然能够全部被检测出来．动脉异常信号2例被误判。结论：从仿真结果可以看出,该算法对房室瓣异常和动脉异常两种心音信号有较高的识别率。尤其对房室瓣杂音能够完全识别,也表明功率谱信息熵在异常心音的识别中具有重要意义。     

Die Doppler-echokardiographische Quantifizierung des regurgitierenden Blutvolumens bei Patienten mit Mitralinsuffizienz

Summary The purpose of this study was to assess the accuracy and clinical utility of pulsed Doppler echocardiography in determining the regurgitant fraction in patients with pure mitral regurgitation. In 30 unselected consecutive patients with mitral regurgitation and in 20 patients without valvular heart disease pulsed Doppler echocardiography was performed to measure blood flow at the mitral and aortic valve. The regurgitant blood volume was calculated as the difference of the stroke volumes measured at the mitral and aortic valve. The regurgitant fraction was computed as regurgitant blood volume/mitral flow. By cardiac catheterization regurgitant blood volume and regurgitant fraction were obtained from the left ventricular angiographic stroke volume and the stroke volume measured by thermodilution. Five patients were excluded because of technically poor left ventricular angiograms. In 4 patients with mitral regurgitation measurement of the regurgitant blood volume and regurgitant fraction was impossible by Doppler because of poor ultrasound signal quality. In 21 patients with mitral regurgitation the correlations between the invasive and the Doppler measurements were significant (regurgitant blood volume:r=0.89, SEE=20.9 ml; regurgitant fraction:r=0.91, SEE=7.1%). However, the mean percent error of the regurgitant fraction measurement (12.0±11.6%) was smaller than of the regurgitant blood volume measurement (24.9±17.0%). In the control group the regurgitant blood volume ranged between –25.1 ml and 11.6 ml and the regurgitant fraction between –17.7% and 12.4%.Thus, pulsed Doppler echocardiography is clinically useful in determination of the regurgitant fraction in 84% of unselected adult patients with pure mitral regurgitation. The Doppler method is limited in the diagnosis and quantification of mild regurgitation. However, the method is more accurate in determining the regurgitant fraction than measuring the regurgitant blood volume.

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Abkürzungsverzeichnis MI Mitralinsuffizienz - RBV regurgitierendes Blutvolumen - RF Regurgitationsfraktion - SV_Angio angiographisch berechnetes Schlagvolumen - SV_Ao Doppler-echokardiographisch an der Aortenklappe gemessenes Schlagvolumen - SV_Mi Doppler-echokardiographisch an der Mitralklappe gemessenes Schlagvolumen - SV_Thermo mittels Thermodilution bestimmtes Schlagvolumen     

Qualitative haemodynamic validation of a percutaneous temporary aortic valve: a proof of concept study

The concept of temporary aortic valves has been suggested in the clinical settings of acute aortic regurgitation and transcatheter aortic valve replacement procedure (TAVR). In TAVR, suggestions have been made to pre-treat or remove the diseased aortic valve prior to implantation of the replacement valve. A successful temporary aortic valve must demonstrate the ability to prevent life-threatening haemodynamics of massive aortic regurgitation. A novel temporary aortic valve (TAV) design, comprised of inflatable balloon elements as a check-valve, can readily be deployed and retrieved via a catheter-system. A simple flow model is set up to test the TAV's performance in severe aortic regurgitation. With induced aortic regurgitation, placement of the TAV is found to increase the distal aortic diastolic pressure, to reduce the widened pulse pressure, to protect proximal aorta-left ventricle from diastolic pressure elevation and to reduce the aortic regurgitant volume. In conclusion, continued development of the TAV system can lead to a successful temporary aortic valve to be used in various appropriate clinical settings.     

基于小波包-交叉频率相干性的肌间耦合特性

人体运动控制系统具有高度的非线性特性,通过量化评价表面肌电(sEMG)信号间的非线性耦合强度,可以得到运动相关肌肉的功能状态,进而探究人体运动控制的机制。本文将小波包分解和n∶m相干性分析相结合,构建基于小波包-n∶m相干性的肌间交叉频率耦合分析模型,探究肌电信号间的非线性耦合关系。在维持30%最大自主收缩力(MVC)的肘部屈伸状态下,采集20名健康成年人的sEMG信号,首先基于小波包分解获取子带分量,然后将子带信号进行n∶m相干性计算,分析肌间耦合特征。结果表明:30%MVC的肘部屈曲运动下,协同肌对和拮抗肌对的线性耦合(频率比为1∶1时)强度高于非线性耦合(频率比为1∶2、2∶1和1∶3、3∶1时);对于肌间非线性耦合,随着频率比的增大,耦合强度随之降低,且频率比为n∶m和m∶n之间没有明显的耦合强度差异;beta和gamma频段内的肌间耦合主要体现在协同肌对之间的线性耦合(1∶1)和低频率比的非线性耦合(1∶2、2∶1)以及拮抗肌对之间的线性耦合上。以上说明:小波包-n∶m相干性方法可以定性、定量地描述肌间非线性耦合强度,为深入揭示人体运动控制机制和运动功能障碍患者的康复评价提供理论参考。     

基于功率谱密度相似性的最佳心音信号选择

心音采集过程中混入的干扰噪声影响着心音诊断,目前多通过手动方式选择干扰较少的信号段做后续分析。为从采集信号中筛选出干扰最少、稳定性最强的最佳心音信号,提出一种最佳心音信号的自动选择方法。对采集的25例正常和119例患先天性心脏病儿童的心音信号,基于离散小波变换与哈达玛积相结合定位心动周期。根据心动周期信号的周期稳定性及功率谱密度相似性计算质量因子,将质量因子最大的连续3个心动周期信号作为最佳心音信号。由心脏病专家通过音频回放对信号选择的成功率和有效性进行评估。结果表明,最佳心音信号自动选择的成功率为95.83%,选择成功信号均包含对应疾病的典型听诊特点。该方法选择性能良好且自动执行,为心音信号的全自动分析提供参考。     

基于小波包变换的癫痫心电信号特征提取

目的:针对癫痫病的检测,从脑电中获取癫痫特征是传统的方法,但是,心电与脑电相结合的诊断方式是未来医疗卫生事业的重要发展方向,所以利用心电信号表征癫痫信息是一个值得研究的课题。方法:小波包变换为心电信号提供了一种十分精细的分析方法,它实现了信号能量在等宽频带上的分解。首先对单周期样本心电信号进行多层小波包分解,重构各个结点的分解系数并提取结点的能量;然后运用最小二乘法对结点能量值进行十次曲线拟合,并提取曲线中的能量极大值点。结果:在0 Hz到0.65 Hz频带内,癫痫心电样本的能量极大值点的频率位置集中在四个特征频带内,而其它心电样本的能量极大值点大部分分布在这四个频带范围以外,这为癫痫病的检测提供了良好的分类特征,实验结果表明本文算法对癫痫病具有较高的识别率。结论:心电信号易于检测且硬件成本低,在医疗中的应用十分频繁,本文算法能够方便的从心电信号中获取癫痫信息,这为癫痫病的检测与诊断提供了一条十分实用的途径。     

An automatic analysis method for detecting and eliminating ECG artifacts in EEG

An automated method for detecting and eliminating electrocardiograph (ECG) artifacts from electroencephalography (EEG) without an additional synchronous ECG channel is proposed in this paper. Considering the properties of wavelet filters and the relationship between wavelet basis and characteristics of ECG artifacts, the concepts for selecting a suitable wavelet basis and scales used in the process are developed. The analysis via the selected basis is without suffering time shift for decomposition and detection/elimination procedures after wavelet transformation. The detection rates, above 97.5% for MIT/BIH and NTUH recordings, show a pretty good performance in ECG artifact detection and elimination.     

The Change of Spectral Energy Distribution of Surface EMG Signal During Forearm Action Process

Spectral energy distribution of surface EMG signal is often used but difficultly and effectively control artificial limb, because the spectral energy distribution changes in the process of limb actions. In this paper, the general characteristics of surface EMG signal patterns were firstly characterized by spectral energy change. 13 healthy subjects were instructed to execute forearm supination （FS） and forearm pronation （FP） with their right foreanns when their forearm muscles were ＂fatigue＂ or ＂relaxed＂. All surface EMG signals were recorded from their right forearm flexor during their right forearm actions. Two sets of surface EMG signals were segmented from every surface EMG signal appropriately at preparing stage and acting stage. Relative wavelet packet energy （symbolized by pnp and pna respectively at preparing stage and acting stage, n denotes the nth frequency band） of surface EMG signal firstly was calculated and then, the difference （Pn = Pna-Pnp） were gained. The results showed that Pn from some frequency bands can effectively characterize the general characteristics of surface EMG signal patterns. Compared with Pn in other frequency bands, P4, the spectral energy change from 93.75 to 125 Hz, was more appropriately regarded as the features.