Cardiovascular Engineering

Impedance cardiography (IC) has been used to monitor the pumping function of the heart in terms of stroke volume or cardiac output. We explored the extent to which IC can be used for monitoring transient effects of cardiac alterations on a beat-to-beat basis. A four-spot-electrode configuration was used in the present design. The spatial arrangement of the four electrodes was carefully selected to obtain an optimal result. A constant current source provided a 4 mA, 20 kHz sinusoidal excitation current. Analog signal processing was developed to demodulate and amplify the resultant impedance information, eliminate low frequency motion artifacts and incidental breathing artifacts. Experiments were performed on normal healthy volunteers. Impedance waveforms were recorded from each subject beginning from a supine position then moving to an upright position. Breath holding was maintained throughout the procedure. The impedance waveform, Z, its first derivative dZ/dt, the DC component, Z(0), and electrocardiogram were recorded simultaneously and continuously. The results showed a significant increase in the relative impedance levels from supine to transient state and then decreased during the upright position. Additionally, the supine position had a higher (dZ/dt)(max) than sitting resulting in a reduction in stroke volume. The increased impedance from supine to sitting verified the physiological findings obtained by others. The results of this investigation illustrate the ability of impedance cardiography to effectively monitor the dynamic cardiovascular function under transient conditions.

Hongjun Zhang

John K-J. Li

Cardiovascular Engineering An International Journal

Cardiovasc Eng

Noninvasive Monitoring of Transient Cardiac Changes with Impedance Cardiography

无创监测瞬时心脏变化的心阻抗图技术

We have developed a novel non-invasive device for the measurement of one of the most sensitive indices of myocardial contractility as represented by the rate of increase of intraventricular pressure (left ventricular dP/dt and arterial dP/dt performance index (dP/dt(ejc)). Up till now, these parameters could be obtained only by invasive catheterization methods. The new technique is based on the concept of applying multiple successive occlusive pressures on the brachial artery from peak systole to diastole using a inflatable cuff and plotting the values against time intervals that leads to the reconstruction of the central aortic pressure noninvasively. The following describes the computer simulator developed for providing a mathematical foundation of the new sensor. At the core of the simulator lies a hemodynamic model of the blood flow on an artery under externally applied pressure. The purpose of the model is to reproduce the experimental results obtained in studies on patients (Gorenberg et al. in Cardiovasc Eng: 305-311, 2004; Gorenberg et al. in Emerg med J 22 (7): 486-489, 2005) and a animal model where ischemia resulted from balloon inflation during coronary catheterization (Gorenberg and Marmor in J Med Eng Technol, 2006) and to describe correlations between the dP/dt(ejc) and other hemodynamic variables. The model has successfully reproduced the trends observed experimentally, providing a solid in-depth understanding of the hemodynamics involved in the new measurement. A high correlation between the dP/dt(ejc) and the rate of pressure rise in the aorta during the ejection phase was observed. dP/dt(ejc) dependence on other hemodynamic parameters was also investigated.

Miguel Gorenberg

Hector Rotztein

Alon Marmor

A New Noninvasive Device for Measuring Central Ejection dP/dt Mathematical Foundation of Cardiac dP/dt Measurement Using a Model for a Collapsible Artery

一种用于测量中心射血dP/dt的新型无创设备：基于可塌陷动脉模型的dP/dt测量数学基础

An innovative method was proposed on the basis of vectorcardiography to characterize the location and extent of moderate to large, relatively compact infarcts using ECG evidence. It is assumed that heart vector is proportional to relevant active depolarization area(s). The normal VCG was then used to examine our ideas based on the information of location, amplitude, and direction of heart vector at any instant that is included in it. The model-based comparison of cases under study and relevant normal VCGs gives region and extent of myocardial infarction. Three criteria were finally defined to evaluate the presented method based on Physionet database. EPD, which is the percentage discrepancy between the extent of the infarct as estimated from our proposed method and as determined from the gold standard. SO, which was defined as the overlap between the sets of infarct segments as estimated and as determined from the gold standard. And CED, which is the distance between the centroid (geometrical center) of the infarct as estimated from our method and as determined from the gold standard. Finally, we gained the values of EPD equal to 32, SO equal to 0.933 and CED equal to 1. The presented method is not applicable in cases of hypertrophy, Bundle Branch Block (BBB) and arrhythmia which can be a plan for future work.

Ali Ghaffari

Mohammad Atarod

Masood Ghasemi

Characterization of the Location and Extent of Myocardial Infarction Using Heart Vector Analysis

利用心脏向量分析法对心肌梗死部位及范围的特征研究

This examination of brachial artery (BA) differential characteristic impedance, DeltaZ (c), illustrates that changes in Z (c) can occur from changes in either BA wall stiffness (Young's modulus, E) and/or its diameter, D. Furthermore, we assessed how changes in both E and D combine in either an isolated, synergistic, or antagonistic manner to yield the net change in BA Z (c). The basis of this analysis is a partial differential equation which approximates DeltaZ (c) as a total differential. The effects on BA DeltaZ (c) of acetylcholine, atenolol, fenoldapine, nitroglycerin, hydrochlorothiazide and other medications are examined using data from previously published studies. Clinical situations which alter BA Z (c), such as congestive heart failure, hypertension, and hyperemia, are also analyzed. Results illustrate the usefulness of the present approach in differentiating how medications, hyperemia, and pathological conditions affect BA DeltaZ (c) by causing independent changes to E and/or D.

Glen Atlas

Brachial Artery Differential Characteristic Impedance: Contributions from Changes in Young’s Modulus and Diameter

肱动脉差分特征阻抗：杨氏模量和直径变化的影响

Pulmonary dysfunction with impairment of lung function and oxygenation is one of the most serious problems in the early postoperative period after cardiac surgery. In this study we investigated the effect of alveolar recruitment strategy during cardiopulmonary bypass on postoperative gas exchange and lung function. This prospective randomized study included 32 patients undergoing elective myocardial revascularization with cardiopulmonary bypass. In 16 patients 5 cm H(2)O of positive end-expiratory pressure was applied after intubation and maintained until extubation (Group I). In the other 16 patients (group II) a positive end expiratory pressure (PEEP) of 5 cm H(2)O was maintained as well but was increased to 14 cm H(2)O every 20 min for 2 min during cross clamp. Measurements were taken preoperatively, before skin incision, before and after (3, 24, 48 h) cardiopulmonary bypass and before discharge (6th postoperative day). Postoperative gas exchange, extravascular lung water and lung function showed no significant difference between the groups. Postoperative pulmonary function variables were lower in both groups compared to baseline values. In patients with normal preoperative pulmonary function, application of an alveolar recruitment strategy during cardiopulmonary bypass does not improve postoperative gas exchange and lung function after cardiac surgery.

Mirela Scherer

Sebastian Dettmer

Dirk Meininger

Heinz Deschka

Galina Geyer

Caroline Regulla

Anton Moritz

Alveolar Recruitment Strategy During Cardiopulmonary Bypass Does Not Improve Postoperative Gas Exchange and Lung Function

心肺转流期间肺泡复张策略不能改善术后气体交换和肺功能

It was in the year 2000, at the turn of the 21st century, my original idea to establish a forum for cardiovascular engineering professionals finally came to fruition. On the invitation of Kluwer Academic Press, the first issue of Cardiovascular Engineering: an International Journal began exactly a decade ago and it was an exciting moment. It has been an endeavor that has taken considerable effort and energy in maintaining timely publications of high quality articles in my role as the Editor-in-chief and in the fulfillment of the many authors’ sense of accomplishment, seeing their research in print of a refereed journal. The Journal was aimed at providing a forum to promote an international scholarly exchange among scientists, clinicians and biomedical engineers with a common interest in the cardiovascular field and with a particular emphasis on the utilization of quantitative and technological methodologies. As such, the Editorial Board members were recommended from nations in North and South America, Asia and Europe. For any new journal to be longstanding and profitable for the publisher, a professional society affiliation is often necessary. Our Journal did not have this leisure. And it came half a decade later, after Springer took over Kluwer, to include the Journal in major citation bodies and providing us with paperless Electronic Manager for manuscript reviews. It has been the contributions from the many authors, as well as the capable effort of some of the editors, production editors and editorial assistants that made uninterrupted quarterly publication of the Journal possible over the decade. In my appreciation, and if I could name a few individual Editorial Board members of their contributions, the late Prof. Leslie Geddes, the Presidential Medal of Technology recipient, would be the first. Known as the ‘‘Father of Cardiovascular Engineering’’, he paved the growth of the field of cardiovascular engineering for several decades. He gave his best support to the Journal and consistently contributing articles of new advances in technology for combating heart disease. We should all marvel his high energy and achievement. Prof. Abraham Noordergraaf, known as the ‘‘Father of Cardiovascular System Dynamics’’ has energized his European collaborators in making contributions to the Journal. Prof. YC Fung, known as the ‘‘Father of Biomechanics’’, has been a kind supporter of the Journal in its inception. So are the continued support from Dr. Peter Kerkhof, Dr. Max Valentinuzzi and Dr. John Clark. Guest editors of the Special Issues which have received high marks were attributed to the wonderful work of Dr. Jerry Batzel and his colleagues from the University of Graz. I had planned to serve as the Editor-in-chief for just a few years, but it quickly turned into a decade. It is time for me to move on to publish my own research work in other highly ranked journals which have missed many of my publications in the past decade, as I chose to publish in Cardiovascular Engineering. I will also return to concentrate on my longneglected fondness of writing books. I will embark on new adventures of writing on exciting topics, and to continue to serve as World Scientific Publishers’ Editor-in-Chief of Bioengineering and Biomedical Engineering Book Series.

Cardiovascular Engineering in the First Decade of the 21st Century

21世纪头十年的心血管工程

A clinical comparison, of two methods of afterload assessment, has been made. The first method, systemic vascular resistance index (SVR(i)), is based upon the traditional formula for afterload which utilizes central venous pressure (CVP), as well as cardiac index (C(i)), and mean arterial blood pressure (MAP). The second method, total systemic vascular resistance index (TSVR(i)), also uses MAP and C(i). However, TSVR(i) ignores the contribution of CVP. This preliminary examination, of 10 randomly-selected ICU patients, has shown a high degree of correlation (ranging from 90 to 100%) between SVR(i) and TSVR(i) (P < 0.0001). Furthermore, there was also a high degree of correlation (ranging from 94 to 100%) noted between the hour-to-hour change in SVR(i) with the hour-to-hour change in TSVR(i) (P < 0.0001). The results, of this pilot study, support the premise that the use of CVP may not always be necessary for afterload evaluation in the clinical setting. Minimally-invasive means of measuring both C(i) and MAP, without CVP, may be adequate for use in assessing afterload.

Jay Berger

Sunil Dhar

Afterload Assessment With or Without Central Venous Pressure: A Preliminary Clinical Comparison

负荷评估有无中心静脉压：一项初步临床比较

The brain is most sensitively dependent on oxygen to maintain its normal function. Methods to assess the degree of its oxygenation have generally been invasive and indirect. Rapid assessment of brain oxygenation is particularly vital during cerebrospinal ischemia and hypoxia. We have developed a noninvasive electro-optical method using pulsed near-infrared (NIR) light to quantify brain oxygenation during ischemia and hypoxia in anesthetized rabbits. Cerebral ischemia was induced through 30-40 s of bi-lateral carotid artery occlusion. Cerebral hypoxia was induced by varying inspired oxygen levels. The NIR light response to the interventions was expressed in terms of relative absorption (RA). Results showed that our pulsed NIR system could rapidly detect sudden alterations in oxygenation and blood flow to the brain. The response patterns during cerebral ischemia and hypoxia were significantly different, although both decreased brain oxygenation. The overall RA response to ischemia was much faster (in seconds) than during hypoxia (in minutes). These different response patterns can serve as early warning signal of low brain oxygenation and to discriminate the cause of the diminished oxygenation. The present pulsed NIR system is capable to provide a rapid, noninvasive and continuous monitoring of such decreases in brain oxygenation.

John K-J Li

Tijun Wang

Rapid Noninvasive Continuous Monitoring of Oxygenation in Cerebral Ischemia and Hypoxia

快速无创连续监测脑缺血和缺氧中的氧合情况

Similar pulse pressure increases and flow reductions have been reported by many investigators, despite dissimilar forms of arterial loading applied. Increased vascular load is most commonly observed due to mechanical and vasoactive interventions. The present study intended to differentiate the hemodynamic contributions of these two forms of arterial loading at closely matched blood pressure levels. To accomplish this, proximal aortic characteristic impedance (Z(o)), total arterial compliance (C), peripheral vascular resistance (R(s)) and time-domain resolved forward (P(f)) and reflected (P(r)) waves were obtained in six anesthetized, thoracotomized and ventilated dogs. Acute loading was accomplished by brief descending thoracic aorta (DTA) occlusion or by intravenous bolus infusion of methoxamine (MTX:5 mg/ml) Systolic pressure increases were matched to a similar extent. Results showed that pulse pressures were drastically increased, reflecting large increases in wave reflections and decreases in arterial compliances. Changes in Z(o), R(s) and C were quantitatively different between the two forms of loading. DTA occlusion primarily increased Z(o) and R(s) with a concurrently large reduction in C. MTX infusion significantly increased small vessel R(s) to the same extent as DTA occlusion, but with a slight decrease in C secondary to an increase in pressure, with Z(o) unchanged. Examination of dynamic loading showed similar increases in reflection coefficients, but P(f) and P(r) were qualitatively different. We conclude that vasoactive methoxamine infusion provides primarily an increased resistive load, while mechanical DTA occlusion provides an increased complex load to the left ventricle. These loads also occur earlier and variably during ventricular ejection.

Ying Zhu

Pamela S. Geipel

Pulse Pressure, Arterial Compliance and Wave Reflection Under Differential Vasoactive and Mechanical Loading

脉压、动脉顺应性和波反射在不同血管活性和机械负荷下的变化

The aim of this study is to describe a robust unified framework for segmentation of the phonocardiogram (PCG) signal sounds based on the false-alarm probability (FAP) bounded segmentation of a properly calculated detection measure. To this end, first the original PCG signal is appropriately pre-processed and then, a fixed sample size sliding window is moved on the pre-processed signal. In each slid, the area under the excerpted segment is multiplied by its curve-length to generate the Area Curve Length (ACL) metric to be used as the segmentation decision statistic (DS). Afterwards, histogram parameters of the nonlinearly enhanced DS metric are used for regulation of the α-level Neyman-Pearson classifier for FAP-bounded delineation of the PCG events. The proposed method was applied to all 85 records of Nursing Student Heart Sounds database (NSHSDB) including stenosis, insufficiency, regurgitation, gallop, septal defect, split sound, rumble, murmur, clicks, friction rub and snap disorders with different sampling frequencies. Also, the method was applied to the records obtained from an electronic stethoscope board designed for fulfillment of this study in the presence of high-level power-line noise and external disturbing sounds and as the results, no false positive (FP) or false negative (FN) errors were detected. High noise robustness, acceptable detection-segmentation accuracy of PCG events in various cardiac system conditions, and having no parameters dependency to the acquisition sampling frequency can be mentioned as the principal virtues and abilities of the proposed ACL-based PCG events detection-segmentation algorithm.

M. R. Homaeinezhad

S. A. Atyabi

E. Daneshvar

A. Ghaffari

M. Tahmasebi

Discrete Wavelet-Aided Delineation of PCG Signal Events via Analysis of an Area Curve Length-Based Decision Statistic

基于面积曲线长度决策统计的离散小波辅助PCG信号事件划分

Publication Information	Publisher: Springer Science + Business Media，Publishing cycle: Bimonthly，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 2003，Proportion of original research papers: 0.00%，Self Citation Rate:N.A.， Gold OA Rate: 0.00%
Average recruitment ratio	网友分享经验：容易

Cardiovascular Engineering

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