When the heart remembers

We present a 61-year-old patient who showed deep T wave inversion on her electrocardiogram (ECG) after cardioversion of her atrial flutter to sinus rhythm. A cardiac catheterization showed normal coronary arteries. The T wave inversion on her ECG is thought to be due to a cardiac memory phenomenon. Cardiac memory is a phenomenon that appears with T wave inversion on ECG after a change in the activation sequence of the heart. It may mimic cardiac ischemia and may mask any condition that appears with T wave abnormality on the ECG.     

Wide QRS complex tachycardia: ECG differential diagnosis.

Wide QRS complex tachycardias (WCT) present significant diagnostic and therapeutic challenges to the emergency physician. WCT may represent a supraventricular tachycardia with aberrant ventricular conduction; alternatively, such a rhythm presentation may be caused by ventricular tachycardia. Other clinical syndromes may also demonstrate WCT, such as tricyclic antidepressant toxicity and hyperkalemia. Patient age and history may assist in rhythm diagnosis, especially when coupled with electrocardiographic (ECG) evidence. Numerous ECG features have been suggested as potential clues to origin of the WCT, including ventricular rate, frontal axis, QRS complex width, and QRS morphology, as well as the presence of other characteristics such as atrioventricular dissociation and fusion/capture beats. Differentiation between ventricular tachycardia and supraventricular tachycardia with aberrant conduction frequently is difficult despite this clinical and electrocardiographic information, particularly in the early stages of evaluation with an unstable patient. When the rhythm diagnosis is in question, resuscitative therapy should be directed toward ventricular tachycardia.     

Emergency management of wide complex tachycardia

Wide complex tachycardia (WCT) is a challenging clinical problem. Priorities in management are the rapid establishment of an appropriate diagnosis and the restoration of sinus rhythm with a minimum of discomfort or danger to the patient. Diagnosis is based upon clinical assessment and analysis of the 12-lead ECG. Pitfalls in the assessment of the 12-lead ECG are reviewed and a simple approach to 12-lead ECG assessment described. Adenosine may be used as a diagnostic test when the underlying rhythm is uncertain. Current recommendations for the treatment of WCT and the role of newer therapies, including trans-cutaneous pacing, are reviewed.     

Holter monitoring for 24 hours in patients with thromboembolic stroke and sinus rhythm diagnosed in the emergency department

It is well known that patients with ischemic stroke show ST-T abnormalities and various rhythm abnormalities on an electrocardiogram (ECG). The most commonly encountered rhythm abnormality is atrial fibrillation. It was recently shown that paroxysmal atrial fibrillation (PAF) is an important causative factor in patients with stroke. Detection of PAF is important in identifying the cause, prognosis, and treatment in patients with thromboembolic stroke. Investigators in the present study followed patients with thromboembolic stroke who had been admitted to the emergency department in sinus rhythm; 24-h Holter monitoring was used, and patients were assessed at referral and every 6 h for 24 h with ECG, which was used to detect rhythm disturbances, especially PAF. In 26 patients with stroke who came to the emergency department, acute thromboembolic stroke was diagnosed on the basis of magnetic resonance imaging; no rhythm abnormalities were noted on Holter monitoring. Eighteen patients were male and 8 were female (mean age: 66±13 y). Arrhythmia was identified on ECG in 3 patients (11%) and on 24-h Holter monitoring in 24 patients (92%). PAF was diagnosed in 3 patients (11%) on ECG and in 11 patients (42%) on Holter monitoring. In 2 patients, nonsustained ventricular tachycardia was detected only on Holter monitoring, which was found to be significantly superior to ECG for the detection of arrhythmias (P < .001). Investigators found no significant relationship between PAF and variables such as hypertension, diabetes, coronary artery disease, history of myocardial infarction, ST-T changes, and elevations in cardiac markers. However, a significant relationship (P < .01) was seen between nonsustained ventricular tachycardia and a history of myocardial infarction. No relationship was discerned between arrhythmia and stroke localization. Study results suggested that (1) PAF is a commonly diagnosed rhythm abnormality, and (2) Holter monitoring is superior to routine ECG for the detection of arrhythmias such as PAF in patients anticipated to have thromboembolic stroke with sinus rhythm.     

Detection of ventricular fibrillation in the presence of cardiopulmonary resuscitation artefacts

Providing cardiopulmonary resuscitation (CPR) to a patient in cardiac arrest introduces artefacts into the electrocardiogram (ECG), corrupting the diagnosis of the underlying heart rhythm. CPR must therefore be discontinued for reliable shock advice analysis by an automated external defibrillator (AED). Detection of ventricular fibrillation (VF) during CPR would enable CPR to continue during AED rhythm analysis, thereby increasing the likelihood of resuscitation success. This study presents a new adaptive filtering method to clean the ECG. The approach consists of a filter that adapts its characteristics to the spectral content of the signal exclusively using the surface ECG that commercial AEDs capture through standard patches. A set of 200 VF and 25 CPR artefact samples collected from real out-of-hospital interventions were used to test the method. The performance of a shock advice algorithm was evaluated before and after artefact removal. CPR artefacts were added to the ECG signals and four degrees of corruption were tested. Mean sensitivities of 97.83%, 98.27%, 98.32% and 98.02% were achieved, producing sensitivity increases of 28.44%, 49.75%, 59.10% and 64.25%, respectively, sufficient for ECG analysis during CPR. Although satisfactory and encouraging sensitivity values have been obtained, further clinical and experimental investigation is required in order to integrate this type of artefact suppressing algorithm in current AEDs.     

Dual mode sensing by a variable cycle ventricular synchronous pulse generator

When the Intermedics Cyberlith pulse generator is operating in its R-wave synchronous (VVT) mode, sensed events may trigger stimulus pulses or inhibit the output circuit. This dual mode response to sensed signals is the result of a variable timing cycle which includes an inhibit alert period (IAP) as well as a synchronous alert period (SAP). Sensed events occurring during the IAP result in inhibition of stimulus pulse output and resetting of the timing circuit. Consequently, during a continuous ECG rhythm strip one may observe synchronous and inhibited sensing responses and slowing of the pacing rate below the programmed rate of the pulse generator.     

Diagnosis of Atrial Arrhythmias Using the Holter Function of a New DDD Pacemaker

The extension of random access memory now makes it possible to store electrocardiographic (ECG) information, referred to here as Holter function (HE), in the memories of new pacemakers, which can be used as diagnostic tools during long-term follow-up. This report describes our experience in 26 consecutive patients for whom the device was used to detect episodes of atrial arrhythmias (AA). An illustrative case is also presented to describe in detail the device's analytical method. Results: Fourteen AA profiles were successfully recorded in 10 patients by the pacemaker HF and correlated with confirmatory simultaneous surface ECG tracings. Three additional profiles were recorded in three other patients without simultaneous ECG recordings. A diagnosis of AA is established when the following findings are combined: (1) in all cases a large number of short interatrial inteivals (A INT); (2) in presence of AV block, interventricular intervals (VINT) stored between the lower programmed pacing rate and the upper rate limit or the fallback rate; (3) in absence of AV block, V INT stored between the basic rate and the AV node refractory period; (4) in case of fallback, (VVI function) no stored AV INT; and (5) in absence of fallback, great variability of AV INT (Wenckebach function). Conclusions: (1) Diagnoses of AA can be made with the pacemaker HE; (2) The homogeneity of the HF profiles makes them useful for long-term follow-up and will probably contribute and clarify the natural history of AA in DDD patients; (3) HF may also serve to monitor the safety and efficacy of antiarrhythmic drug therapy during long-term follow-up.     

从体表电生理信号中提取希氏束信号的分析系统

背景:传统的希氏束检测方法是对体表心电信号进行数百次叠加或者经食道检测以及心内导管检测得到,研制从体表心电信号提取希氏束信号不但有利于临床诊断,也有利于动物药物实验.目的:从体表心电信号中提取希氏束信号,并开发体表希氏束信号分析系统.方法:以家兔体表心电信号作为待分析信号,以其心内希氏束电图作为对照信号,采用随机共振、小波变换、叠加平均和耦合累加等分析方法,对体表心电信号进行分析.结果与结论:小波变换后得到的信号,可以从体表心电信号中检测出希氏束信号,但并不是所有希氏束信号都能被识别,心内信号经过小波变换后,个别希氏束信号反而消失.随机共振方法从体表心电中检测出的希氏束信号识别率要高于小波分析方法,随机共振方法与小波分析相同之处是,心内信号经过处理后,个别希氏束信号反而消失.本文提出的耦合叠加算法能够从体表心电信号提取出希氏束信号,与经典叠加方法比较,其优点是希氏束信号明显,叠加次数远远少于经典叠加方法.提示实验采用的随机共振、小波变换、耦合累加等分析方法,能够有效抑制噪声、提取希氏束信号,开发研制的体表希氏束信号分析系统具有较强的实用价值.     

Remote Electrocardiographic Monitoring with a Wireless Implantable Loop Recorder: Minimizing the Data Review Burden

Introduction: Currently available implantable loop recorders (ILRs) are hampered by limited memory, sensing artifacts, and need for manual memory download. Remote monitoring techniques that automatically transfer stored recordings for review may enhance ILR utility. However, automatic electrocardiograph (ECG) detection and transmission of an excessive number of tracings directly to physicians may be burdensome. This pilot study assessed the utility of direct ILR transmission to a central ECG monitoring center on the burden of data to be reviewed by the physician. Methods: Patients with unexplained syncope were implanted with a novel ILR with automatic (i.e., independent of patient intervention) wireless telemetry download. Transmitted recordings underwent a two‐step review process: initial algorithmic filtering followed by human overread at a monitoring center using predefined criteria. Results: Forty patients were enrolled and followed for 8.5 ± 5.1 months. A total of 223,226 ECG recordings were transmitted to the monitoring center (on average 660 per patient per month). Algorithmic filtering eliminated 191,305 ECGs as artifact (89%), with monitoring center overread of 31,921 strips. Ultimately, 117 relevant ECGs were selected for further evaluation by the physician (0.0053%). One or more relevant ECGs were identified for 20 patients (50%). Conclusions: Automatic ILR recording and wireless technique is feasible for remote ECG monitoring by ILRs. However, sensitive criteria for recording and transmission may result in an excessive ECG burden. The two‐step screening process in this pilot study minimized physician overread time while providing clinically relevant recordings in a substantial proportion of patients. (PACE 2010; 1347–1352)     

心电监护影响因素分析

分析影响监护仪显示的各项参数及图像因素。认为电极接触不良及干扰、仪器感知功能不良是影响心率及心律显示准确的主要因素，测量部位、袖带松紧度及病人体位是影响血压显示准确的因素。提出了识别和排除影响因素的方法     

A comparison between EASI system 12-lead ECGs and standard 12-lead ECGs for improved clinical nursing practice

Aims and objectives. This study was carried out to verify the accuracy of 12‐Lead ECG, obtained through a continuous ECG monitoring system with five cables positioned in EASI mode, to identify basic ECG alterations. Background. This study concerns continuous ECG monitoring systems in Coronary Care Units. Continuous ECG monitoring is an important device for nursing surveillance and is useful in decreasing adverse events. Design and method. Thirteen patients admitted consecutively to the Coronary Care Unit for Acute Myocardial Infarction underwent daily and simultaneous recording of a12‐lead ECG using both procedures: EASI ECG and STANDARD ECG. A sample of 1164 ECG leads acquired in EASI mode was compared with a sample of as many ECG leads acquired using the standard procedure with a traditional cardiograph. Results and conclusions. In the Coronary Care Unit, Continous ECG monitoring with five cables positioned in EASI mode is a valid alternative to the standard 12‐lead ECG for cardiac rhythm abnormalities detection and for acute myocardial ischemia and old myocardial infarction assessment. Therefore, the EASI system might be advantageous for long‐term patient monitoring. Relevance to clinical practice. The EASI system represents a valid device for the nursing surveillance of patients who need continuous ECG monitoring, improves clinical nursing practice in Coronary Care Units, supports the reduction of adverse events such as cardiac arrest and reduces the hospital costs.     

Model-based Bayesian filtering of cardiac contaminants from biomedical recordings

Electrocardiogram (ECG) and magnetocardiogram (MCG) signals are among the most considerable sources of noise for other biomedical signals. In some recent works, a Bayesian filtering framework has been proposed for denoising the ECG signals. In this paper, it is shown that this framework may be effectively used for removing cardiac contaminants such as the ECG, MCG and ballistocardiographic artifacts from different biomedical recordings such as the electroencephalogram, electromyogram and also for canceling maternal cardiac signals from fetal ECG/MCG. The proposed method is evaluated on simulated and real signals.     

Eliminating cardiac contamination from myoelectric control signals developed by targeted muscle reinnervation

The electrocardiogram (ECG) artifact is a major noise contaminating the myoelectric control signals when using shoulder disarticulation prosthesis. This is an even more significant problem with targeted muscle reinnervation to develop additional myoelectric sites for improved prosthesis control in a bilateral amputee at shoulder disarticulation level. This study aims at removal of ECG artifacts from the myoelectric prosthesis control signals produced from targeted muscle reinnervation. Three ECG artifact removal methods based on template subtracting, wavelet thresholding and adaptive filtering were investigated, respectively. Surface EMG signals were recorded from the reinnervated pectoralis muscles of the amputee. As a key parameter for clinical myoelectric prosthesis control, the amplitude measurement of the signal was used as a performance indicator to evaluate the proposed methods. The feasibility of the different methods for clinical application was also investigated with consideration of the clinical speed requirements and memory limitations of commercial prosthesis controllers.     

Subtraction of 16.67 Hz railroad net interference from the electrocardiogram: application for automatic external defibrillators

The widespread application of automatic external defibrillators (AEDs) for treating out-of-hospital cardiac arrest incidents and their particular use at railway stations defines the task for 16.67 Hz power line interference elimination from the electrocardiogram (ECG). Although this problem exists only in five European countries, it has to be solved in all AEDs, which must comply with the European standard for medical equipment requirements for interchangeability and compatibility between rail systems. The elimination of the railroad interference requires a specific approach, since its frequency band overlaps with a significant part of the frequencies in the QRS spectra. We present a method based only on one channel ECG signal processing, which effectively subtracts the interference components. The computation procedure is based on simple signal processing tools, which include: (i) bi-directional band-pass filtering (13-23 Hz) of the analyzed ECG segment; (ii) estimation of adequate linearity thresholds; (iii) frequency measurement and calculation of dynamic interference buffer in linear segments and (iv) phase synchronization and subtraction technique in nonlinear segments. The developed method has proved advantageous in providing sufficient quality of the output interference free ECG signal for seven defined arrhythmia types (normal sinus rhythm, normal rhythm, supraventricular tachicardia, slow/rapid ventricular tachycardia, and coarse/fine ventricular fibrillation), and simulated interferences with constant or variable frequencies and amplitudes, which cover the entire amplitude range of the input channel. The procedure is suitable to be embedded in AEDs as a preprocessing branch, which proves reliable for analysis of ECG signals, thus guaranteeing the specified accuracy of the AED automatic rhythm analysis algorithms.     

Chest pain in a young female

Acute Coronary Syndrome (ACS) is a common diagnosis in the emergency department (ED), the most severe manifestation of which is ST elevation on electrocardiogram (ECG). ST elevation reflects obstruction of flow through the coronary arteries, most commonly due to coronary atherosclerotic plaque rupture. However, alternative causes of coronary obstruction causing ST elevation are possible. Spontaneous coronary artery dissection (SCAD) is an unusual cause of ST elevation in ED patients which providers may encounter in patients without traditional atherosclerosis risk factors. Patients presenting with SCAD as a cause of ST elevation require unique management from traditional ACS. Here we report a case of a 43?year old female presenting with chest pain and unusual ECG findings including accelerated idioventricular rhythm followed by subtle ST segment elevation and resolution of abnormalities. This case illustrates subtle clinical and ECG findings suggestive of SCAD which emergency physicians should consider when evaluating patients for ACS in the absence of traditional clinical presentations. Such considerations may prompt physicians to avoid therapy for coronary plaque rupture which is not indicated in patients with SCAD.     

Paroxysmal tachycardia in children and teenagers with normal sinus rhythm and without heart disease

The purpose of this study was to evaluate the value of esophageal programmed stimulation in children and teenagers with normal sinus rhythm ECG and normal noninvasive studies, having palpitations and syncope, and no documented tachycardias. Paroxysmal tachycardias are frequent in children and are often related to accessory connection. These tachycardias are sometimes difficult to prove. Transesophageal atrial pacing was performed at rest and during infusion of isoproterenol in 31 children or adolescents aged 9-19 years (16 +/- 3 years) with normal sinus rhythm ECG and suspected or documented episodes of paroxysmal tachycardia. Sustained tachycardia was induced in 27 patients, at rest in 13 patients, and after isoproterenol in 14 remaining patients. Atrioventricular nodal reentrant tachycardia was found as the main cause of paroxysmal tachycardia (22 cases). Six patients were followed by a vagal reaction and dizziness. These patients had spontaneous tachycardia with syncope. In three other patients, atrial fibrillation was also induced. Concealed accessory pathway reentrant tachycardia was identified in three patients. In two patients, a regular wide tachycardia with right bundle branch block morphology was induced; the diagnosis of verapamil-sensitive ventricular tachycardia was made in a second study by intracardiac study. In conclusion, atrioventricular nodal reentrant tachycardia was found as the main cause of symptoms in children with normal sinus rhythm ECG. Syncope is frequently associated and provoked by a vagal reaction. This diagnosis could be underestimated in adolescents frequently considered as hysterical because noninvasive studies are negative.     

Evaluation of a subject-specific transfer-function-based nonlinear QT interval rate-correction method

The QT interval in the electrocardiogram (ECG) is a measure of total duration of depolarization and repolarization. Correction for heart rate is necessary to provide a single intrinsic physiological value that can be compared between subjects and within the same subject under different conditions. Standard formulas for the corrected QT (QTc) do not fully reproduce the complexity of the dependence in the preceding interbeat intervals (RR) and inter-subject variability. In this paper, a subject-specific, nonlinear, transfer function-based correction method is formulated to compute the QTc from Holter ECG recordings. The model includes five parameters: three describing the static QT-RR relationship and two representing memory/hysteresis effects that intervene in the calculation of effective RR values. The parameter identification procedure is designed to minimize QTc fluctuations and enforce zero correlation between QTc and effective RR. Weighted regression is used to better handle unbalanced or skewed RR distributions. The proposed optimization approach provides a general mathematical framework for further extensions of the model. Validation, robustness evaluation and comparison with existing QT correction formulas is performed on ECG signals recorded during sinus rhythm, atrial pacing, tilt-table tests, stress tests and atrial flutter (29 subjects in total). The resulting average modeling error on the QTc is 4.9 ± 1.1 ms with a sampling interval of 2 ms, which outperforms correction formulas currently used. The results demonstrate the benefits of subject-specific rate correction and hysteresis reduction.     

联合机能试验负荷模型下的动态心电评价

摘要 目的：联合机能试验负荷条件下,通过动态心电监测,快速筛选运动时心血管风险、评价运动强度和体能储备。 方法：对10例体育学硕士研究生在联合机能试验的标准负荷条件下进行连续负荷心电图描记,并对动态心电图监测结果进行研究。 结果：心率加速、匀速和减速时R波电压比较结果中,大部分个例（51.72%）及总体反应出的左室电压均在心率加速时较高;将29人次中RRn/RRn+1与R波电压具有相关性的22人次作加速度、3加速度、5加速度、15加速度与对应R波电压的线性回归分析,分别有16人次、18人次、20人次和22人次,差异有显著性意义（P＜0.05）,具有线性回归关系;对总数据分析结果显示,除3加速度外,其余均具有线性回归关系;总体心电散点图呈现为窦性心律和运动负荷诱发的窦速,伴偶发房早。 结论：在联合机能试验条件下,心功失代偿之前,或可以心脏实际负荷推测躯体外周负荷,联合应用心电散点图分析技术,在既定运动量下（如联合机能试验）实时的全程动态心电监测,或可以作为运动时心血管风险快筛、运动强度和体能储备快速识别、运动强度精确评价的参考方法。