Kinetics of the electrocardiographic changes after permanent coronary occlusion in rats: Relationship with infarct size

The electrocardiogram (ECG) has been a useful tool to identify ischemia in humans and laboratory animals. Previous ECG studies showed that presence of pathological Q waves in lead DI in rats submitted to ligature of the left coronary artery (LCA) is a good predictor of successful myocardial infarction (MI). This study aimed to determine the sensitivity and the specificity of these ECG findings to predict successful MI. Male Wistar rats were submitted to surgical ligature of the LCA (N = 86) or sham-operation (SO, N = 16). ECG was recorded under halothane/ether anesthesia before surgery and 1, 3, 5, 7, and 15 days later. MI was determined by the presence of a transmural fibrous scar. Sixty-nine rats survived and 60 showed fibrous scar indicating a successful production of MI (18 and 42 animals were analyzed 1 or 15 days after MI, respectively). Twenty-four hours after, Q amplitude was linearly related to infarct size (r = ?0.778; P < 0.01), but not 15 days after (r = ?0.416; P > 0.05). In 53 out of 60 rats with transmural scar, Q wave in lead DI was identified in the ECG. Absence of Q wave occurred in 7 animals. The sensitivity was 88% (CI₉₅ = 83–93%). Nine animals submitted to coronary ligature did not show infarct scar. One of these animals, however, showed Q wave in DI, indicating a specificity of 77% (CI₉₅ = 65–104%). In conclusion, ECG can be used as a reliable tool to identify MI and can be used to predict the infarct size as earlier as 1 day after LCA ligation in rats.     

Identification of post-myocardial infarction patients with ventricular tachycardia by time-domain intra-QRS analysis of signal-averaged electrocardiogram and magnetocardiogram

A new time-domain analysis method, which quantifies ECG/MCG intra-ORS fragmentation, is applied to parts of the QRS complex to identify postmyocardial infarction patients with ventricular tachycardia. Three leads of signalaveraged electrocardiograms and nine leads of magnetocardiograms were band-pass filtered (74Hz to 180Hz). The filtered signals showed fragmentation in the QRS region, which was quantified by the number of peaks M and a score S, that is the product of M and the sum of the peak amplitudes. Both parameters were determined for the first 80 ms of the QRS complex and the total QRS complex in each channel. For classification, the mean-values of the parameters M and S of the three electrical leads and the nine magnetic leads were calculated. Late potential and late field analyses were performed for the same signals. 31 myocardial infarction patients were included, 20 of them with a history of documented ventricular tachycardia (VT). Identification of VT patients using the SAECG led to better results (sensitivity 95%, specificity 91%) considering the entire QRS complex than with the standard late potential analysis suggested by Simson (sensitivity 90%, specificity 73%). For the SAMCG and the entire QRS complex results using the parameters S and M are also better (sensitivity 95%, specificity 100%) than for the late field analysis (sensitivity 90% and specificity 100%). For the first 80 ms, the performance of the parameters M and S is only slightly decreased.     

Flexible microelectrode arrays to interface epicardial electrical signals with intracardial calcium transients in zebrafish hearts

The zebrafish (Danio rerio) is an emerging genetic model for regenerative medicine. In humans, myocardial infarction results in the irreversible loss of cardiomyocytes. However, zebrafish hearts fully regenerate after a 20% ventricular resection, without either scarring or arrhythmias. To study this cardiac regeneration, we developed implantable flexible multi-microelectrode membrane arrays that measure the epicardial electrocardiogram signals of zebrafish in real-time. The microelectrode electrical signals allowed for a high level of both temporal and spatial resolution (~20 μm), and the signal to noise ratio of the epicardial ECG was comparable to that of surface electrode ECG (7.1 dB vs. 7.4 dB, respectively). Processing and analysis of the signals from the microelectrode array demonstrated distinct ECG signals: namely, atrial conduction (P waves), ventricular contraction (QRS), and ventricular repolarization (QT interval). The electrical signals were in synchrony with optically measured Calcium concentration gradients in terms of d[Ca²⁺]/dt at both whole heart and tissue levels. These microelectrodes therefore provide a real-time analytical tool for monitoring conduction phenotypes of small vertebral animals with a high temporal and spatial resolution.     

Age and Sex Dependent Variations in the Normal Magnetocardiogram Compared with Changes Associated with Ischemia

Magnetocardiography is the measurement of the magnetic fields of the heart. Human studies performed in magnetically shielded laboratories have demonstrated that magnetocardiograms (MCGs) can detect ischemia. The aim of this study was to obtain clinically useful MCGs in an unshielded hospital room. Other objectives included understanding the normal variations in MCG during repolarization and determining the MCG parameters that best discriminate patients with ischemia from healthy controls. We measured 51 healthy volunteers of both sexes from 25 to 76 years of age and 11 patients with documented exercise-induced ischemia. Resting and postexercise measurements were taken, and several MCG parameters were defined. For 19 of 29 MCG parameters, there were significant differences between healthy females and males (p < or = 0.05). For nine MCG parameters, there were differences between older and younger healthy subjects (p < 0.01). Therefore the age and sex of a subject should be considered when evaluating the MCG. Thirteen parameters separated the patients from the controls (areas under the receiver operating characteristic curve >80%). The repolarization stabilization interval, a parameter based on the time-evolution of contour maps, performed the best. Magnetocardiography performed in clinical settings is a potential screening tool for ischemia that should be further explored.     

Magnetocardiographic and Electrocardiographic Exercise Mapping in Healthy Subjects

In 12-lead electrocardiography (ECG), detection of myocardial ischemia is based on ST-segment changes in exercise testing. Magnetocardiography (MCG) is a complementary method to the ECG for a noninvasive study of the electric activity of the heart. In the MCG, ST-segment changes due to stress have also been found in healthy subjects. To further study the normal response to exercise, we performed MCG mappings in 12 healthy volunteers during supine bicycle ergometry. We also recorded body surface potential mappings (BSPM) with 123 channels using the same protocol. In this paper we compare, for the first time, multichannel MCG recorded in bicycle exercise testing with BSPM over the whole thorax in middle-aged healthy subjects. We quantified changes induced by the exercise in the MCG and BSPM with parameters based on signal amplitude, and correlation between signal distributions at rest and after exercise. At the ST-segment and T-wave apex, the exercise induced a magnetic field component outward the precordium and the minimum value of the MCG signal over the mapped area was found to be amplified. The response to exercise was smaller in the BSPM than in the MCG. A negative component in the MCG signal at the repolarization period of the cardiac cycle should be considered as a normal response to exercise. Therefore, maximum ST-segment depression over the mapped area in the MCG may not be an eligible parameter when evaluating the presence of ischemia. © 2001 Biomedical Engineering Society. PAC01: 8719Nn, 8719Hh, 8780Tq     

The study of position of antilingula, midwaist of mandibular ramus and midpoint between coronoid process and gonion in relation to lingula of 92 Thai dried mandibles as potential surgical landmarks for vertical ramus osteotomy

This study aims to investigate positions of the antilingula (AL), the midwaist of the mandibular ramus (MW) and the midpoint between the coronoid process and the gonion (MCG) in relation to the lingula of dried mandibles. Bilateral rami of 92 Thai dried mandibles were studied. The AL, the MW, the MCG and the corresponding position of the tip of lingula (L) were marked on the external aspect of the mandibular ramus. The distances from the AL, the MW and the MCG to the L were measured in the anterior–posterior and the superior–inferior planes using computerized image analysis. The results showed the AL was discernible in 80.4% of lateral mandibular rami studied. The most of the AL was found anterior–superior to the L with a maximum distance of 5.9 mm anteriorly and 8.2 mm superiorly. The MW was frequently located anterior–inferior to the L with a maximum distance of 9.3 mm anteriorly and 9.9 mm inferiorly. The majority of the MCG was found anterior–superior to the L with a maximum distance of 9.6 mm anteriorly and 8.9 mm superiorly. A 5 mm radius from the L included 84.5% of the AL, 81.5% of the MW and 79.4% of the MCG. Medians (interquartiles) of distances from the AL, the MW and the MCG to the L were 3.4 (2.3–5.0) mm, 3.8 (2.5–5.3) mm and 4.1 (2.8–5.3) mm, respectively. In conclusion, the AL was identified in 80.4% of lateral mandibular rami studied. The AL and the MCG were commonly found anterior–superior to the lingula, whereas the MW was mostly observed anterior–inferior to the lingula. Therefore, a cut made more than a 5 mm posterior or superior to these landmarks would be in 79% of cases, within a statistically safe area avoiding encroaching upon the inferior alveolar neurovascular bundle passing immediately lateral to the lingula. Although the MW and the MCG might be alternative surgical guides when the AL is absent, their use alone as surgical landmarks is not recommended.     

基于密集连接卷积神经网络的下壁心肌梗死检测

下壁心肌梗死是一种病死率高的急性缺血性心脏病,易诱发恶性心律失常、心率衰竭、心源性休克等危及生命的并发症。因而,开展对下壁心肌梗死准确高效的早期诊断研究具有重要的临床价值。心电图是早期诊断下壁心肌梗死最敏感的手段。本文提出了一种基于密集连接卷积神经网络的下壁心肌梗死检测方法。该方法将Ⅱ、Ⅲ和aVF导联的原始心电信号串接数据作为模型的输入,利用卷积层的尺度不变性提取心电信号中具有鲁棒性的特征,并通过不同层间密集连接的方式加强了心电信号特征的传递,使得网络能够自动学习心电信号中鲁棒性强且辨识度高的有效特征,从而实现下壁心肌梗死的准确检测。本文还采用德国国家计量学研究所诊断公共心电数据库进行验证,本文模型的准确率、敏感性和特异性分别达到了99.95%、100%和99.90%。在含有噪声的情况下,模型的准确率、敏感性和特异性也均超过99%。基于本文研究结果,期望今后可在临床环境中引入本文方法,以帮助医生快速诊断下壁心肌梗死。     

Reduction of QTD - A Novel Marker of Successful Reperfusion in NSTEMI. Pathophysiologic Insights by CMR

Background/Objectives: Non-ST segment elevation myocardial infarction (MI) poses similar detrimental long-term prognosis as ST-segment elevation MI. No marker on ECG is established to predict successful reperfusion in NSTEMI. QT dispersion is increased by myocardial ischemia and reduced by successful restoration of epicardial blood flow by PCI. Whether QT dispersion reduction translates to smaller infarcts and thus indicates successful reperfusion is unknown.We hypothesized that the relative reduction of QT dispersion (QTD-R_rel ) on a standard ECG in acutely reperfused NSTEMI is related to infarct size and infarct transmurality as assessed by delayed enhancement CMR (DE-CMR).Methods and Results: 69 patients with a first acute NSTEMI were included. QTD-R_rel was stratified according to LV function and volumes, infarct transmurality and size as assessed by DE-CMR. Extensive myocardial infarction was defined as above median infarct size.LV function and end-systolic volume were only mildly related to QTD-R_rel . QTD-R_rel was inversely related to infarct size (r=-0.506,p=0.001) and infarct transmurality (r=-0.415, p=0.001). QTD-R_rel was associated with extensive myocardial infarction in univariate analysis (odds ratio (OR) 0.958, CI 0.935-0.982; p=0.001). Compared to clinical and angiographic data QTD-R_rel remained the only independent predictor of non-transmural infarcts (OR 1.110, CI 1.055-1.167; p=0.049).Conclusion: In patients with acute Non-ST-Segment Myocardial infarction QTd-R_rel calculated on a surface ECG prior and post PCI for restoration of epicardial blood flow detects small, non-transmural infarcts as assessed by delayed enhancement CMR. Thus, QTd-R_rel can indicate successful reperfusion therapy.     

Repolarization Heterogeneity of Magnetocardiography Predicts Long-Term Prognosis in Patients with Acute Myocardial Infarction

PurposeMagnetocardiography (MCG) has been proposed as a noninvasive, diagnostic tool for risk-stratifying patients with acute myocardial infarction (AMI). This study evaluated whether MCG predicts long-term prognosis in AMI.ResultsMACE occurred in 31 (25%) patients, including 20 revascularizations, 8 deaths, and 3 re-infarctions. Non-dipole patterns were observed at the end of the T wave in every patients. However, they were observed at T-peak in 77% (24/31) and 54% (50/93) of patients with and without MACE, respectively (p=0.03). Maximum current, field map angles, and distance dynamics were not different between groups. In the multivariate analysis, patients with non-dipole patterns at T-peak had increased age- and gender-adjusted hazard ratios for MACE (hazard ratio 2.89, 95% confidence interval 1.20–6.97, p=0.02) and lower cumulative MACE-free survival than those with dipole patterns (p=0.02).ConclusionNon-dipole patterns at T-peak were more frequently observed in patients with MACE and were related to poor long-term prognosis. Thus, repolarization heterogeneity measured by MCG may be a useful predictor for AMI prognosis.     

Novel indices of ventricular repolarization to screen post myocardial infarction patients

We propose novel indices of ventricular repolarization intervals, the JTp/JT, Tpe/JTp and Tpe/JT ratios. These indices have been compared with the duration of the ventricular repolarization intervals and other ratios in 17 normal subjects and 17 patients with old myocardial infarction. In the intervals and other ratios, the best separation between groups is obtained with the Tpe/QTp and Tpe/QT ratios with 94% sensitivity and 82% specificity, the proposed ratios increased sensitivity to 100% and specificity to 94%. These indices should be further tested to determine their usefulness in discriminating between OMI patients with and without susceptibility to ventricular arrhythmias.     

Shock Advisory System for Heart Rhythm Analysis During Cardiopulmonary Resuscitation Using a Single ECG Input of Automated External Defibrillators

Minimum “hands-off” intervals during cardiopulmonary resuscitation (CPR) are required to improve the success rate of defibrillation. In support of such life-saving practice, a shock advisory system (SAS) for automatic analysis of the electrocardiogram (ECG) contaminated by chest compression (CC) artefacts is presented. Ease of use for the automated external defibrillators (AEDs) is aimed and therefore only processing of ECG from usual defibrillation pads is required. The proposed SAS relies on assessment of outstanding components of ECG rhythms and CC artefacts in the time and frequency domain. For this purpose, three criteria are introduced to derive quantitative measures of band-pass filtered CC-contaminated ECGs, combined with three more criteria for frequency-band evaluation of reconstructed ECGs (rECG). The rECGs are derived by specific techniques for CC waves similarity assessment and are reproducing to some extent the underlying ECG rhythms. The rhythm classifier embedded in SAS takes a probabilistic decision designed by statistics on the training dataset. Both training and testing are fully performed on real CC-contaminated strips of 10 s extracted from human ECGs of out-of-hospital cardiac arrest interventions. The testing is done on 172 shockable strips (ventricular fibrillations VF), 371 non-shockable strips (NR) and 330 asystoles (ASYS). The achieved sensitivity of 90.1% meets the AHA performance goal for noise-free VF (>90%). The specificity of 88.5% for NR and 83.3% for ASYS are comparable or even better than accuracy reported in literature. It is important to note that, the aim of this SAS is not to recommend shock delivery but to advice the rescuers to “Continue CPR” or to “Stop CPR and Prepare for Shock” thus minimizing “hands-off” intervals.     

Circulating lectin pathway proteins do not predict short-term cardiac outcomes after myocardial infarction

Despite improvements in treatment, coronary artery disease is still responsible for one-third of all deaths globally, due predominantly to myocardial infarction (MI) and stroke. There is an important potential in developing new strategies for treatment of patients with these conditions. Inflammation, and in particular the actions of the complement system, has emerged as part of the pathogenesis in reperfusion injury in patients with MI. To further qualify this, we examined the association between the plasma levels of lectin pathway proteins and myocardial end-points, left ventricular ejection fraction (LVEF) and infarct size in a cohort of patients with ST-elevation myocardial infarction (STEMI). A blood sample was drawn the day after percutaneous coronary intervention from 73 patients with STEMI. The primary end-points, LVEF and infarct size, were measured with magnetic resonance imaging 6–9 days after the infarct. Complement pattern-recognition molecules of the lectin pathway (mannan-binding lectin, H-ficolin, L-ficolin and M-ficolin) were analysed along with soluble membrane attack complex (sMAC) and C-reactive protein (CRP) in plasma with immunofluorometric assays <50%. CRP correlated negatively with LVEF, regression coefficient = –0·17 (P = 0·01). None of the lectin pathway proteins correlated to LVEF or infarct size, nor did soluble membrane attack complex (sMAC). There were no differences in plasma levels of these complement proteins when comparing patients with ejection fraction <50% to patients with ejection fraction <50%. Pattern-recognition molecules of the lectin pathway and sMAC do not predict short-term cardiac outcomes after MI.     

Cerebral hemodynamics and pseudo‐continuous arterial spin labeling considerations in adults with sickle cell anemia

Sickle cell anemia (SCA) is a genetic disorder resulting in reduced oxygen carrying capacity and elevated stroke risk. Pseudo‐continuous arterial spin labeling (pCASL) measures of cerebral blood flow (CBF) may have relevance for stroke risk assessment; however, the effects of elevated flow velocity and reduced bolus arrival time (BAT) on CBF quantification in SCA patients have not been thoroughly characterized, and pCASL model parameters used in healthy adults are often applied to patients with SCA. Here, cervical arterial flow velocities and pCASL labeling efficiencies were computed in adults with SCA (n = 19) and age‐ and race‐matched controls without sickle trait (n = 7) using pCASL in sequence with phase contrast MR angiography (MRA). Controls (n = 7) and a subgroup of patients (n = 8) also underwent multi‐post‐labeling‐delay pCASL for BAT assessment. Mean flow velocities were elevated in SCA adults (velocity = 28.3 ± 4.1 cm/s) compared with controls (velocity = 24.5 ± 3.8 cm/s), and mean pCASL labeling efficiency (α) was reduced in SCA adults (α = 0.72) relative to controls (α = 0.91). In patients, mean whole‐brain CBF from phase contrast MRA was 91.8 ± 18.1 ml/100 g/min, while mean pCASL CBF when assuming a constant labeling efficiency of 0.86 was 75.2 ± 17.3 ml/100 g/min (p < 0.01), resulting in a mean absolute quantification error of 23% when a labeling efficiency appropriate for controls was assumed. This difference cannot be accounted for by BAT (whole‐brain BAT: control, 1.13 ± 0.06 s; SCA, 1.02 ± 0.09 s) or tissue T₁ variation. In conclusion, BAT variation influences pCASL quantification less than elevated cervical arterial velocity and labeling efficiency variation in SCA adults; thus, a lower labeling efficiency (α = 0.72) or subject‐specific labeling efficiency should be incorporated for SCA patients.     

Effects of digital resolution on characterisation of cardiac late potentials

The effects of amplitude resolution in the signal-averaged ECG are studied in relation to the analysis of cardiac late potentials. The statistical properties of ECG signals from 22 patients after myocardial infarction were investigated in terms of amplitude distribution and noise level for the material. It was found that unbiased averaging could be achieved using a resolution greater than 10 μV. The noise levels of the bandpass-filtered individual X, Y and Z leads (range of 1–10 μV) and the vector magnitude were also investigated. Marked intra-lead differences in noise level were found, indicating that analysis based on individual leads is preferable. The effects of quantisation noise on the vector magnitude were negligible for amplitude resolutions below 5 μV. However, the additional noise contribution at 5 μV could be compensated by a moderate increase in acquisition time. The sensitivity to noise was considered when determining the endpoint of the filtered QRS complex using the vector magnitude.     

Association of ABO histo‐blood group B allele with myocardial infarction

To investigate a possible association of ABO blood group alleles with myocardial infarction, a case–control study comprising 177 patients (median age 57.0 years; range 32–72 years) and 89 controls was performed. The distributions of the ABO blood‐genotype O₁, O₂, A₁, A₂ and B alleles were assessed by analysis of genomic DNA, using the sequence‐specific primer–polymerase chain reaction (PCR‐SSP) technique to investigate exons VI and VII on chromosome 9. The prevalence of the B allele was 2.5 times higher amongst patients with a history of myocardial infarction than amongst controls (16.3 vs. 6.7%; P = 0.034, Fisher's exact test). There was an association between patients carrying the B allele and myocardial infarction, with an odds ratio (OR) of 2.7 (95% confidence interval 1.1–6.8). The B allele remained an independent risk factor for myocardial infarction (P = 0.038) when classical risk factors were adjusted for by unconditional logistic regression. In conclusion, the ABO blood group B allele was found to be an independent risk factor for myocardial infarction.     

Electromagnetic Field at 15.95–16 Hz is Cardio Protective Following Acute Myocardial Infarction

Previous studies have shown that pre-exposure of the heart to weak magnetic field reduces infarct size shortly after induction of myocardial ischemia. To investigate the role of AC magnetic field with a frequency of 15.95–16 Hz and 80 mT on left ventricular (LV) remodeling following chronic coronary occlusion and a short episode of ischemia followed by reperfusion (I/R). LV dimension and function were measured using echocardiography. Femur bone marrow was isolated and cells were phenotyped for endothelial linage and immuno stained for endothelial cells. The area at risk was measured using triphenyltetrazolium chloride staining. A significant reduction of 27% in shortening fraction (SF) was measured following acute myocardial infarction (AMI) compared with a 7% decrease in animals exposed to magnetic field (p < 0.04). A significantly higher number of colony forming units and endothelial progenitor cells were counted within the treated groups subjected to magnetic field (p < 0.02). Exposing the heart to magnetic field prior to reperfusion did not show any preservation either on SF or on infarct size. Magnetic field was protective in the AMI but not in the I/R model. The mechanisms underlying cardiac protection induced by AC magnetic field following chronic injury deserves further investigation.     

Segmentation of Holter ECG Waves Via Analysis of a Discrete Wavelet-Derived Multiple Skewness–Kurtosis Based Metric

In this study, a simple mathematical-statistical based metric called Multiple Higher Order Moments (MHOM) is introduced enabling the electrocardiogram (ECG) detection–delineation algorithm to yield acceptable results in the cases of ambulatory holter ECG including strong noise, motion artifacts, and severe arrhythmia(s). In the MHOM measure, important geometric characteristics such as maximum value to minimum value ratio, area, extent of smoothness or being impulsive and distribution skewness degree (asymmetry), occult. In the proposed method, first three leads of high resolution 24-h holter data are extracted and preprocessed using Discrete Wavelet Transform (DWT). Next, a sample to sample sliding window is applied to preprocessed sequence and in each slid, mean value, variance, skewness, and kurtosis of the excerpted segment are superimposed called MHOM. The MHOM metric is then used as decision statistic to detect and delineate ECG events. To show advantages of the presented method, it is applied to MIT-BIH Arrhythmia Database, QT Database, and T-Wave Alternans Database and as a result, the average values of sensitivity and positive predictivity Se = 99.95% and P+ = 99.94% are obtained for the detection of QRS complexes, with the average maximum delineation error of 6.1, 4.1, and 6.5 ms for P-wave, QRS complex, and T-wave, respectively showing marginal improvement of detection–delineation performance. In the next step, the proposed method is applied to DAY hospital high resolution holter data (more than 1,500,000 beats including Bundle Branch Blocks—BBB, Premature Ventricular Complex—PVC, and Premature Atrial Complex—PAC) and average values of Se = 99.97% and P+ = 99.95% are obtained for QRS detection. In summary, marginal performance improvement of ECG events detection–delineation process, reliable robustness against strong noise, artifacts, and probable severe arrhythmia(s) of high resolution holter data can be mentioned as important merits and capabilities of the proposed algorithm.     

Analysis of myocardial infarction signals using optical technique

The risk of heart attack or myocardial infarction (MI) may lead to serious consequences in mortality and morbidity. Current MI management in the triage includes non-invasive heart monitoring using an electrocardiogram (ECG) and the cardic biomarker test. This study is designed to explore the potential of photoplethysmography (PPG) as a simple non-invasive device as an alternative method to screen the MI subjects. This study emphasises the usage of second derivative photoplethysmography (SDPPG) intervals as the extracted features to classify the MI subjects. The statistical analysis shows the potential of “a-c” interval and the corrected “a-cC” interval to classify the subject. The sensitivity of the predicted model using “a-c” and “a-cC” is 90.6% and 81.2% and the specificity is 87.5% and 84.4%, respectively.