Assessment of the humane aspects of electric lancing of whales by measurement of current densities in the brain and heart of dead animals

The potential physiological effects of the electric lance are assessed, as used in Japanese whaling operations. Current densities are measured in the brains and hearts of six whales to which a controlled current of 5 A is applied by two electrodes inserted at various sites in the carcasses. The whales vary in size from 1.8 m (200 kg) to 16 m (40 t). The minimum current density in the brain necessary to cause depolarisation of neurones is estimated to be 10 mA cm⁻² and to cause ventricular fibrillation is estimated to be 0.5 mA cm⁻². No current densities exceeding 4.8 mA cm⁻² are recorded in the brain. Very few recordings of current density from the heart are above 0.5 mA cm⁻², and they occurr only when electrodes are in optimal positions. When electrodes are placed as in whaling operations, no whale over 3 m in length would receive current densities in the heart or brain sufficient to cause permanent dysfunction. It is concluded that electric lancing is ineffective as a secondary method of killing whales and that the current densities recorded could cause pain and suffering to an already distressed animal.     

基于心磁信号的电流密度分析方法研究

电流密度向量分析是心磁图仪临床应用中的关键诊断技术,其重构与分类效果将直接影响心脏疾病筛查的准确度。研究一种电流密度分析方法,包括电流密度重构逆向算法,并提出一种电流密度自动分类新算法。将该电流密度分析方法应用于27例健康志愿者和75例心肌缺血患者的临床验证:首先,使用四通道心磁图仪SQUID传感器采集36个测量点位心磁信号源数据,采用标准Ⅱ导联心电数据同步化心磁信号源数据;其次,应用基于傅里叶变换的逆向求解算法,重构每例受试者电流密度分布,自动计算3项电流密度分类参数CDI、IPCD、E_RT,并通过多元线性回归模型确定自动分类算法中健康组和心肌缺血组的线性判别函数;最后,借助基于KL熵值计算和线性判别函数的自动分类新算法,对重构后的电流密度进行自动分类。结果表明:健康组与心肌缺血组间3项分类参数CDI、IPCD、E_RT显著性差异分别为2.0×10^-11、2.7×10^-5和3.0×10^-4;CDI、IPCD、E_RT诊断心肌缺血的敏感性分别为73%、81%和60%,特异性分别为100%、65%和73%;自动分类结果的敏感性、真阳性率、特异性、假阳性率和真阴性率分别为89.33%、100%、100%、0%和76.47%。实验说明,所述电流密度分析方法可靠、准确度高,可用于临床心肌缺血诊断。     

INDUCTION OF SIALYL LEWISX ON THE SURFACE OF CULTURED RAT VASCULAR ENDOTHELIAL CELLS AND CARDIAC MYOCYTES BY HYPOXIA/REOXYGENATION IN VITRO

Neutrophils adhere to and roll on vascular endothelial cells (VECs) through interaction of selectins and their carbohydrate ligands in the early stages of inflammation; this adhesion is then later strengthened through interaction of integrins on neutrophils with intercellular adhesion molecule-1 (ICAM-1) on endothelial cells. Recent, as yet unpublished studies showed that myocardial ischaemia/reperfusion caused rapid expression of sialyl Lewis^X (SLe^X), one of the carbohydrate ligands of selectins, on VECs and cardiac myocytes and that an anti-SLe^X monoclonal antibody (MAb) significantly reduced myocardial reperfusion injury in vivo . In the present study, to investigate whether or not ischaemia/reperfusion itself can induce the expression of SLe^X on VECs and cardiac myocytes, the expression of SLe^X on cultured rat VECs and cardiac myocytes was examined by treatment with hypoxia/reoxygenation in vitro , because ischaemia/reperfusion stimuli may partly be due to hypoxia/reoxygenation. The expression of SLe^X was induced rapidly and temporarily on the surface of cultured rat cardiac myocytes and VECs by hypoxia/reoxygenation in vitro . This strongly suggests that the expression of SLe^X on the surface of myocardial cells is induced initially and directly by ischaemia/reperfusion, which results in the rolling attachment of neutrophils in the early stages of myocardial reperfusion injury.     

Delay of development of transmural irreversible ischaemic injury in canine myocardium

Summary During the course of experimentally induced myocardial ischaemia affected tissue initially suffers reversible ischaemic injury or, if ischaemia persists, injury of increasing severity before becoming irreversibly damaged. This state is characterized by tissue necrosis and referred to as myocardial infarction. The purpose of this study was to investigate whether it is possible to delay or perhaps even prevent the development of irreversible ischaemic injury. Ischaemia was induced by coronary artery occlusion (CAO) in canine hearts for 90 min or 24 h. The drug used for intervention was hyaluronidase. Ischaemic damage was assessed by p-NBT staining and ultrastructural evaluation of tissue biopsies. Development of irreversible ischaemic damage was prevented during 90 min of CAO. However, progression of reversible to irreversible ischaemic injury could not be prevented during 24 h of CAO. In conclusion, it is possible to prevent the development of irreversible ischaemic injury by a suitable intervention during the early stages of ischaemia in the canine heart and thus to gain time for additional intervention in the early treatment of myocardial infarction.     

Diagnosis of the acute ischaemic heart by ion elution from myocardium.

The post-mortem diagnosis of acute myocardial ischaemia may be difficult to establish in the absence of morphological changes in the myocardium or recent coronary thrombosis. Ischaemic cell injury leads to potassium (K) efflux and sodium (Na) influx and, if the blood is still circulating, the K:Na ratio of the tissue falls. In this study, the K:Na ratio was measured by eluting the ions from samples of myocardium and assaying the eluate. The method yields similar results to those obtained by a previous method, in which myocardial samples were homogenized. The K:Na ratios on samples of horizontal slices through the heart were plotted on maps of the slices. A low K:Na ratio corresponded to, but extended beyond, areas where there was morphological evidence of ischaemia. The method is simple and may be of use in routine practice.     

从CT数据到带纤维走向的全心脏有限元模型的建立

心脏计算机模型是研究生理/病理心脏功能及心律失常治疗方法的有力工具,心脏有限元解剖模型是构建各种心脏模型的基础。从病人的临床影像数据建立个性化的心脏有限元模型,可为临床诊断治疗提供极大便利。研究一种由人体胸腔CT影像数据建立全心脏有限元模型的方法,具体步骤包括:基于胸腔CT影像,通过MIMICS建立心脏解剖面片模型;根据HyperMesh修复面片模型,得到心脏实体有限元模型。由于心肌纤维走向与心脏的电/机械活动密切相关,在从影像数据重建心脏解剖结构之后,又特别研究心肌纤维走向确定方法。首先,利用规则库方法(rule-based approach)确定心室肌纤维走向;之后,在使用规则库方法的基础上,利用结构张量分析(structure tensor analysis)进行平滑滤波,得到心房肌纤维走向。为验证心肌纤维走向的正确性,分析使用该方法计算得到的巴克曼束、左心房后部、左上心房后部、房间沟等几个典型部位处心肌纤维方向与X轴的夹角,分别为4.97°±4.84°(均值±标准差)、111.99°±3.72°、178.89°±3.73°、86.48°±4.01°,符合文献报道的心肌纤维走向的观测结果。所提出的方法可从心脏影像数据构建包含心肌纤维走向的心脏有限元模型,为各类心脏建模仿真研究打下基础。     

Estimation of the tissue damage after MI through time-frequency analysis of the electromechanical signals

Abstract

Coronary congestion is a heart disease that puts many lives at risk each year. The task of coronary arteries is to distribute blood to the heart tissue and any blockage in them can cause the tissue to absorb less oxygen and nutrients than needed (ischaemia disease). This imbalance will continue until the first cell is destroyed (myocardial infarction). Simulating the myocardial infarction in the laboratory rats, this study tries to determine the extent of tissue damage through the electrocardiogram (ECG) and atrial blood pressure (ABP) synchronic signals. The signals of 50 wistar rats with a weight range of 200–300?g were recorded at 30?min in the normal case and 30?min in the ischaemia and myocardial infarction (MI) case (the artificial complete blockage was in the left anterior descending coronary artery (LAD)). For a different injury in the rats’ heart, the vasopressin (AVP) with different doses was injected to 40 rats. After that the images of the heart sections and the data were extracted, the 50-dimensional feature vector was generated by using the wavelet packet transform (WPT) on the ECG and ABP signals and also by obtaining the entropy of the wavelet coefficients. The extent of tissue damage on the images of the heart tissue was extracted by using the image processing method. Finally, the amount of the damaged tissue was estimated by four artificial neural networks (ANN) (with different structures) with an averaging criterion. The intelligent machine estimated the ischaemia and normal tissues with the average error of 2.91% for all the AVP doses and control cases.     

Regional myocardial heat-shock protein (HSP70) concentrations under different blood flow conditions

 The concentration of heat-shock proteins of 70 kD (HSP70) in heart tissue has been shown to increase during transient myocardial ischaemia and to persist during several hours of reperfusion. In this study the relationship between the local myocardial HSP70 concentration and blood flow was addressed for control physiological conditions and acute myocardial ischaemia. A specific aim of this study was to address the question of whether low flow areas under control physiological conditions have undergone a transient ischaemia during the preceding hours and thus may be in a state of hibernation or stunning. In 12 anaesthetized, open-chest beagle dogs (6 control and 6 with 60-min coronary artery stenosis) heart rate, mean aortic pressure, mean arterial partial pressure of O₂ and partial pressure of CO₂ averaged 85±16 beats/min, 94±14 mmHg, 102±17 mmHg and 39±6 mmHg, respectively. Regional HSP70 and myocardial blood flow (RMBF) were measured using an HSP70-enzyme-linked immunosorbent assay and the tracer microsphere technique, respectively, in samples of 250 mg wet mass. In the control group the mean RMBF was 1.06±0.59 ml·min^–1·g^–1 and the local HSP70 concentration was 7.08±1.03 μg/mg cytosolic protein. Myocardial HSP70 showed a blood flow-independent regional biological heterogeneity, equivalent to a coefficient of variation of 0.31. Local HSP70 concentrations did not differ (P>0.05) between control low and high flow samples, 6.16±1.0 vs 6.08±0.75 μg/mg cytosolic protein, respectively. However, after 60 min of coronary artery occlusion the local HSP70 concentration increased from 7.08 ±1.03 to 13.43±3.19 μg/mg cytosolic protein (P<0.001). There was a significant inverse relationship between the percent reduction of local blood flow and HSP70 (r=–0.56, P<0.001). From these results it is concluded that: (1) low flow samples under control physiological conditions are unlikely to be in a state of hibernation or stunning since their HSP70 concentration is normal and (2) the increase in the local HSP70 concentration during myocardial ischaemia reflects the degree of impairment of O₂ delivery. Received: 29 May 1998 / Received after revision: 14 August 1998 / Accepted: 25 August 1998     

60 Hz ventricular fibrillation thresholds for large-surface-area electrodes

The paper describes a series of animal experiments in which large-surface-area disk electrodes were used to study the current density required for ventricular fibrillation. The electrical currents were introduced to the heart both by applying the electrodes directly to the heart and by applying the electrodes to the surface of the chest near the heart. The electrode areas studied ranged from 1000 to 30 000 mm². The results show that, for large-area electrodes, fibrillation thresholds are determined by current density. The thresholds approach a constant value of 3·5 μA mm⁻²     

Hyponatraemia aggravates cardiac susceptibility to ischaemia/reperfusion injury

Hyponatraemia is defined as a serum sodium concentration of <135 mEql/L and is the most common electrolyte disturbance in patients with chronic heart failure. We hypothesize that hyponatraemia may induce Ca²⁺ overload and enhance reactive oxygen species (ROS) production, which will exacerbate myocardial injury more than normonatraemia. We investigated the effect of hyponatraemia on the ability of the heart to recover from ischaemia/reperfusion episodes. Cardiomyocytes were obtained from 1‐ to 3‐day‐old Sprague Dawley rats. After isolation, cardiomyocytes were placed in Dulbecco's modified Eagle's medium (DMEM) containing low sodium concentration (110, 120, or 130 mEq/L) or normal sodium concentration (140 mEq/L) for 72 hours. Exposure of cardiomyocytes to each of the low‐sodium medium significantly increased both ROS and intracellular Ca²⁺ levels compared with the exposure to the normal‐sodium medium. In vivo, 8‐week‐old male Sprague Dawley rats were divided into four groups: control group (Con), furosemide group (Fur), low‐sodium diet group (Lsd) and both furosemide and low‐sodium diet group (Fur + Lsd). The hearts subjected to global ischaemia exhibited considerable decrease in left ventricular developed pressure during reperfusion, and the size of infarcts induced by ischaemia/reperfusion significantly increased in the Fur, Lsd and Fur + Lsd compared with that in the Con. Hyponatraemia aggravates cardiac susceptibility to ischaemia/reperfusion injury by Ca²⁺ overload and increasing in ROS levels.     

Relationship between ischaemic time and ischaemia/reperfusion injury in isolated Langendorff‐perfused mouse hearts

Myocardial functional recovery and creatine kinase (CK) release following various periods of ischaemia were investigated in isolated mouse hearts. The hearts were perfused in the Langendorff mode with pyruvate‐containing Krebs–Hensleit (KH) buffer under a constant perfusion pressure of 80 mmHg, and were subjected to either continuous perfusion or to 5, 15, 20, 25, 30, 45 or 60 min of global ischaemia followed by 45 min of reperfusion. In hearts subjected to ischaemic periods of 5, 15 or 20 min, there was a transient reduction in the left ventricular (LV) dP/dt max during the early phase of reperfusion, while the recovery at the end of reperfusion reached a level similar to that in hearts subjected to continuous perfusion. In hearts subjected to longer ischaemic periods, i.e. 25, 30, 45 or 60 min, the decrease in the cardiac performance was more pronounced and persistent, with significantly lower recovery in LV dP/dt max and higher LV end diastolic pressure (LVEDP) at the end of reperfusion than in the non‐ischaemic hearts. There were no significant differences in the recoveries in coronary flow or in heart rate (HR) between groups. Similarly to the functional recovery, the release of CK showed a clear ischaemic length‐related increase. In conclusion, the Langendorff‐perfused isolated mouse heart could be a valuable model for studies of myocardial ischaemia/reperfusion injury. Future studies using gene‐targeted mice would add valuable knowledge to the understanding of myocardial ischaemia/reperfusion injury.     

Wavelet transform analysis of heart rate variability during myocardial ischaemia

Analysis of heart rate variability (HRV) is a valuable, non-invasive method for quantifying autonomic cardiac control in humans. Frequency-domain analysis of HRV involving myocardial ischaemic episodes should take into account its non-stationary behaviour. The wavelet transform is an alternative tool for the analysis of non-stationary signals. Fourteen patients have been analysed, ranging from 40 to 64 years old and selected from the European Electrocardiographic ST-T Database (ESDB). These records contain 33 ST episodes, according to the notation of the ESDB, with durations of between 40s and 12min. A method for analysing HRV signals using the wavelet transform was applied to obtain a time-scale representation for very low-frequency (VLF), low-frequency (LF) and high-frequency (HF) bands using the orthogonal multiresolution pyramidal algorithm. The design and implementation using fast algorithms included a specially adapted decomposition quadrature mirror filter bank for the frequency bands of interest. Comparing a normality zone against the ischaemic episode in the same record, increases in LF (0.0112±0.0101 against 0.0175±0.0208s²Hz⁻¹; p<0.1) and HF (0.0011±0.0008 against 0.0017±0.0020s²Hz⁻¹; p<0.05) were obtained. The possibility of using these indexes to develop an ischaemic-episode classifier was also tested. Results suggest that wavelet analysis provides useful information for the assessment of dynamic changes and patterns of HRV during myocardial ischaemia.     

Remote vs. local ischaemic preconditioning in the rat heart: infarct limitation,suppression of ischaemic arrhythmia and the role of reactive oxygen species

The unmet clinical need for myocardial salvage during ischaemia–reperfusion injury requires the development of new techniques for myocardial protection. In this study the protective effect of different local ischaemic preconditioning (LIPC) and remote ischaemic preconditioning (RIPC) protocols was compared in the rat model of myocardial ischaemia–reperfusion, using infarct size and ischaemic tachyarrhythmias as end‐points. In addition, the hypothesis that there is involvement of reactive oxygen species (ROS) in the protective signalling by RIPC was tested, again in comparison with LIPC. The animals were subjected to 30‐min coronary occlusion and 90‐min reperfusion. RIPC protocol included either transient infrarenal aortic occlusion (for 5, 15 and 30 min followed by 15‐min reperfusion) or 15‐min mesenteric artery occlusion with 15‐min reperfusion. Ventricular tachyarrhythmias during test ischaemia were quantified according to Lambeth Conventions. It was found that the infarct‐limiting effect of RIPC critically depends on the duration of a single episode of remote ischaemia, which fails to protect the heart from infarction when it is too short or, instead, too prolonged. It was also shown that RIPC is ineffective in reducing the incidence and severity of ischaemia‐induced ventricular tachyarrhythmias. According to our data, the infarct‐limiting effect of LIPC could be partially eliminated by the administration of ROS scavenger N‐2‐mercaptopropionylglycine (90 mg/kg), whereas the same effect of RIPC seems to be independent of ROS signalling.     

The time factor in relation to the pattern,progress and prognosis of coronary atherosclerosis

A hypothesis is presented to explain the bewildering sequence of signs and symptoms in ischaemic heart attacks. Based on current knowledge of the pathophysiology of myocardial ischaemia, it is suggested that symptoms depend mainly on the acuteness of the ischaemia and pathological changes on the length of time it persists.     

Fundamental criteria underlying the efficacy and safety of defibrillating current waveforms

The efficacy (threshold average current density) and safety factor (overdose current density for a 50 per cent decrease in myocardial contractility) were determined for the rectangular, trapezoidal and damped sine wave defibrillating current waveforms using a new blood-perfused, isolated, working canine heart in an isoresistive and isotonic volume conductor. This preparation permits the achievement of defibrillation with the heart in as uniform a current density field as possible and eliminates myocardial deterioration due to the traditional loss of coronary perfusion during ventricular fibrillation. Since the heart is isolated, it is not subject to any neural influences. It was found that, for a given pulse duration, the threshold average current density (efficacy) values were very similar among the three current waveforms. It was also found that the safety factors for the three current waveforms ranged from 3·2 to 5·3, the conventional 4–6 ms damped sine wave having a safety factor of 5·0±0·9 (1SD).     

Relationship between ischaemic time and ischaemia/reperfusion injury in isolated Langendorff-perfused mouse hearts

Myocardial functional recovery and creatine kinase (CK) release following various periods of ischaemia were investigated in isolated mouse hearts. The hearts were perfused in the Langendorff mode with pyruvate-containing Krebs-Hensleit (KH) buffer under a constant perfusion pressure of 80 mmHg, and were subjected to either continuous perfusion or to 5, 15, 20, 25, 30, 45 or 60 min of global ischaemia followed by 45 min of reperfusion. In hearts subjected to ischaemic periods of 5, 15 or 20 min, there was a transient reduction in the left ventricular (LV) dP/dt max during the early phase of reperfusion, while the recovery at the end of reperfusion reached a level similar to that in hearts subjected to continuous perfusion. In hearts subjected to longer ischaemic periods, i.e. 25, 30, 45 or 60 min, the decrease in the cardiac performance was more pronounced and persistent, with significantly lower recovery in LV dP/dt max and higher LV end diastolic pressure (LVEDP) at the end of reperfusion than in the non-ischaemic hearts. There were no significant differences in the recoveries in coronary flow or in heart rate (HR) between groups. Similarly to the functional recovery, the release of CK showed a clear ischaemic length-related increase. In conclusion, the Langendorff-perfused isolated mouse heart could be a valuable model for studies of myocardial ischaemia/reperfusion injury. Future studies using gene-targeted mice would add valuable knowledge to the understanding of myocardial ischaemia/reperfusion injury.     

Cholinergic agonists may produce preservation of myocardial ischaemia/reperfusion injury

The best treatment for myocardial infarction is to restore blood flow in the ischaemic region, though it will bring new myocardial damage known as myocardial ischaemia/reperfusion (I/R) injury. Both the ischaemia preconditioning and the ischaemia postcondioning have been shown to reduce the myocardial I/R injury, but their deficits restrict wide clinical availability. It has been demonstrated that inflammation plays a critical role in the I/R injury process. Also plasma levels of cytokines and inflammation response can be regulated by specifically augmenting cholinergic signaling via the efferent vagus nerve and α7 subunit-containing nicotinic acetylcholine receptor (α7nAChR). Because cholinergic modalities, acting through vagus nerve- and/or α7nAChR-mediated mechanism, have been confirmed to suppress excessive inflammation during the I/R injury in kidney, liver, lung and intestine, therefore, we hypothesize that cholinergic agonists may also provide a protection for the myocardial I/R injury.     

Validity of the microdialysis technique for experimental in vivo studies of myocardial energy metabolism

OBJECTIVES: The validity of the microdialysis technique for experimental in vivo studies of myocardial energy metabolism is not known. To address this question interstitial levels of energy-related metabolites (lactate, adenosine, inosine and hypoxanthine) obtained by the microdialysis technique were compared with corresponding metabolites from myocardial biopsies at given intervals in a porcine heart model using different protocols of ischaemia and reperfusion. METHODS: In an open chest porcine heart model, interstitial levels of energy-related metabolites were monitored using the microdialysis technique. All animals (n = 23) were subjected to 120-min pretreatment followed by 40 min of regional ischaemia and 120 min of reperfusion. Tissue biopsies were obtained in the beginning, middle and at the end of the 40-min ischaemic period and at the end of the reperfusion period. Pretreatment consisted of either rest (group 1, n = 7), or rest for 90 min and one ischaemia/reperfusion (10 + 20 min) cycle (group 2, n = 9), or four ischaemia/reperfusion cycles (10 + 20 min each) (group 3, n = 7). RESULTS: Interstitial levels of energy-related metabolites monitored by the microdialysis technique correlated with tissue biopsy levels of lactate (r = 0.90, P < 0.001), adenosine (r = 0.89, P < 0.001), inosine (r = 0.88, P < 0.001) and hypoxanthine (r = 0.91, P < 0.001), respectively, which were obtained by tissue biopsies at given time intervals. These significant correlations were valid regardless of the functional state of the myocardium. CONCLUSION: We observed significant correlations between microdialysis probe levels and tissue biopsy levels of energy-related metabolites in both ischaemic and non-ischaemic tissue. These data assess the validity of the microdialysis technique (in the current setting) for studying dynamic changes of myocardial energy metabolism.     

Cardiovascular haemodynamics and ventriculo-arterial coupling in an acute pig model of coronary ischaemia–reperfusion

Although reperfusion after coronary occlusion is mandatory for myocardial salvage, reperfusion may trigger a cascade of harmful events (reperfusion injury) adding to myocardial injury. We investigated effects of reperfusion on left ventricular (LV) haemodynamics and ventriculo-arterial (VA) coupling in pigs following acute myocardial ischaemia induced by coronary artery occlusion. Experiments were performed in six animals, with measurements of cardiac and arterial function at baseline, after 60 min of ischaemia (T60) and after 2 (T180) and 4 h of reperfusion (T300). Ventriculo-arterial coupling was assessed using the ventriculo-arterial elastance ratio of paper, as well as using a 'stiffness coupling' and 'temporal coupling' index. Reperfusion following ischaemia (T180 versus T60) induced a progressive decline in cardiovascular function, evidenced by a decrease in mean arterial blood pressure, cardiac output and ejection fraction which was not restored at T300. Although reperfusion also induced an increase in slope of the end-systolic pressure-volume relationship (ESPVR), the ESPVR curve shifted to the right, associated with a depression of contractile function. Histology demonstrated irreversible myocardial damage at T300. The ventriculo-arterial elastance ratio and the 'stiffness coupling' index were unaffected throughout the protocol, but the 'temporal coupling' parameter indicated a relative shift between heart period and the time constant of the arterial system. It is unlikely that these alterations are attributable to ischaemic injury alone. The combination of both the stiffness and temporal coupling index may provide more information when studying ventriculo-arterial coupling than the more commonly used ventricular end-systolic stiffness/effection arterial elastance (E(es)/E(a)) ratio.     

Topical cardiac cooling--computer simulation of myocardial temperature changes

Topical cardiac cooling (TC) is often used in cardiac surgery. We used a computer simulation to study temperature changes in the heart, especially in the right ventricular wall. A three-dimensional computer heart model, derived from Visible Human Data set, National Library of Medicine was used. The model is made from cubes, with spatial resolution of 1mm. Explicit Finite Different method and temperature diffusion equation were used to calculate new temperatures. Three different simulations were performed and simulated temperatures were drawn on a cross-section of heart model in different colors. The results show that areas not immersed into TC solution are less protected against ischemia. It is important not to rely solely on topical cooling but use appropriate method of myocardial protection technique.