How Can We Identify the Best Implantation Site for an ECG Event Recorder?

ZELLERHOFF, C., et al. : How Can We Identify the Best Implantation Site for an ECG Event Recorder? The aim of this study was to show how to find the preferable implantation site for an ECG event recorder (ECG‐ER). We compared the quality of bipolar ECG recordings (4‐cm electrode distance, vertical position) in 65 patients at the following sites: left and right subclavicular, left and right anterior axillary line (4th‐5th interspace), left and right of the sternum (4th‐5th interspace), heart apex, and subxyphoidal. The results were compared to the standard ECG lead II. In 30 patients, an additional comparison between vertical and horizontal ECG registrations was done using the same sites. ECG signals in five patients were compared positioning the electrodes towards the skin with turning them towards the muscle during ECG‐ER implantation. The best ECG quality (defined as highest QRS amplitude, best visible P wave and/or pacemaker spike, best measurable QRS duration, and QT interval) and best agreement with the standard lead II was found in 68% on the left of the sternum, significantly less often (P < 0.001 ) on the right of the sternum (14.1%), left subclavicular (6.9%), apical (5.5%) and subxyphoidal (4.2%). A significantly higher QRS amplitude was measured and the P wave was more often visible in the vertical electrode position than in the horizontal position. In all five ECG‐ER patients, there was a good agreement between the bipolar surface ECG at the implantation site and ECG‐ER stored signals. A significant noise signal occurred in all five patients when the ECG‐ER was implanted with electrodes towards the muscle. A P wave was visible in only three of those patients, but there was an insignificantly higher QRS amplitude than in ECG‐ERs implanted with electrodes towards the skin. From these results, it can be concluded that the best implantation site for an ECG‐ER is right or left of the sternum, positioning the electrodes vertically and towards the skin.     

Electrocardiographic artifacts due to electrode misplacement and their frequency in different clinical settings

Misplacement of electrodes can change the morphology of an electrocardiogram (ECG) in clinical important ways. To assess the frequency of these errors in different clinical settings, we collected ECGs routinely performed at the cardiology outpatient clinic and the intensive care unit. Lead misplacement was suspected when one of the following morphological changes occurred: QRS axis between 180 degrees and -90 degrees , positive P wave in lead aVR, negative P waves in lead I and/or II, very low (<0.1 mV) amplitude in an isolated peripheral lead, or abnormal R progression in the precordial leads. We analyzed 838 ECGs and identified 37 ECGs suspicious for electrode misplacement, from which 7 were confirmed. The frequency of ECG artifacts due to switched electrodes was 0.4% (3/739) at the outpatient clinic and 4.0% (4/99) at the intensive care unit (P = .005). In conclusion, errors in ECG performance do occur with an increasing frequency in an acute medical care setting.     

胸腔镜辅助心外膜电极植入同步化治疗慢性心功能不全

目的探讨胸腔镜辅助心外膜电极植入同步化（CRT）治疗慢性心功能不全的效果。方法 3例心肌病慢性心功能衰竭患者经心电图和超声心动图明确诊断心衰伴心脏不同步运动,DSA下植入左室起搏电极失败后采用胸腔镜辅助小切口植入左室心外膜起搏电极完成CRT。术后观察血流动力学、并发症、起搏参数、监护室和住院时间、心功能状况、心电图QRS波群时限的变化、超声心动图心脏同步运动状况。结果所有患者手术过程顺利,左室电极固定可靠,起搏阈值≤1 V。CRT治疗后心电图QRS波群时限〈120 ms,超声心动图示心脏同步运动较术前明显好转。均于手术当日下午拔除气管插管,血流动力学指标平稳,于术后第2日转回普通病房。病例1和2术后1周出院,术后3月心功能恢复至Ⅱ级;病例3术后第3日出现急性肾功能衰竭,予持续肾脏替代治疗无效,术后第7天并发多脏器功能衰竭死亡。结论胸腔镜辅助植入心外膜电极CRT可用于慢性心衰的治疗,可作为介入方法失败后的选择,远期疗效还有待进一步的观察。     

Prevalence and characteristics of idiopathic outflow tract tachycardia with QRS alteration following catheter ablation requiring additional radiofrequency ablation at a different point in the outflow tract

Subtle variations in QRS morphology occurs during idiopathic outflow tract ventricular tachycardia (OTVT), but no studies have clarified the prevalence and characteristics of the OTVT with altered QRS morphology following radiofrequency catheter ablation (RFA), which then require an additional RF application at a different portion of the outflow tract to abolish OTVT. Of 202 patients with a monomorphic VT or premature ventricular contraction (PVC) originating from the outflow tract, 6 (3%) showed changes in QRS morphology in the OTVT following RFA, requiring an additional RF application to the outflow tract at a different portion. In all six patients, RFA was applied for the first or second OTVT to a right or left ventricular endocardial site, with the other site being the left sinus of Valsalva. In each patient, OTVT before or after the changes in QRS morphology had characteristic ECG findings originating from a particular portion of the outflow tract. Changes in QRS morphology consistently included an increase or decrease in R wave amplitude in all inferior leads. Detailed continuous observation of QRS morphology in OTVT, especially R wave amplitude in inferior leads, is important for identifying changes of QRS morphology during catheter ablation. Mapping and ablation at a different portion of the outflow tract is then needed for cure.     

Bronchial electrocardiography to determine left or right main bronchial placement of an endotracheal suction catheter tip

Objective To assess the utility of a blue lined angle tiped and electrode tipped catheter, to guide left and right main bronchus cannulation.Design A prospective studySetting An 11-bed general intensive care unit in a 900-bed teaching hospital.Patients 50 intubated intensive care patients, in sinus rhythm with normal P and QRS mean frontal axis, who required endobronchial suctioning for routine respiratory management.Interventions Endobronchial electrocardiography was used to position a blue lined angle tiped and electrode tiped suction catheter into the right and left main bronchi.Results Selective cannulation of the left main bronchi was determined by observing a biphasic or inverted P wave in 42 patients, or biphasic or inverted QRS complex in 31 patients. In 8 patients in whom no changes in the ECG were found, bronchoscopic placement of an ECG electrode into the left main bronchus demonstrated a biphasic or inverted P wave in 8 patients and a biphasic QRS complex in 3 patients, confirming the failure to cannulate the left main bronchus in these 8 patients.Conclusions Using a blue lined, angle tipped and electrode tipped catheter for endotracheal suctioning, endobronchial electrocardiography may be a simple method to signal left or right main bronchus cannulation.     

Sensing Characteristics of Unipolar and Bipolar Orthogonal Floating Atrial Electrodes: Morphology and Spectral Analysis

We investigated wave morphology and spectral energy distributions of signals picked up by floating atrial unipolar and bipolar orthogonal sensing electrodes. Our data show that atrial P and QRS waves from unipolar floating electrodes are comparable. On the other hand, atrial P and QRS waves from bipolar orthogonal floating electrodes are significantly different. Even at high and mid right atrial locations, QRS waves are either absent or much smaller in amplitude and lower in frequency content than P waves. We conclude that the bipolar orthogonal floating atrial electrode is superior to the unipolar one for sensing due to its P to QRS wave discriminating power, which makes complex input filters or algorithms unnecessary. Our data support the idea that physiologic pacing with a VDD or VAT pacemaker is possible using a single pass lead.     

The resting electrocardiogram in the management of patients with congestive heart failure: established applications and new insights

The resting electrocardiogram (ECG) furnishes essential information for the diagnosis, management, and prognostic evaluation of patients with congestive heart failure (CHF). Almost any ECG diagnostic entity may turn out to be useful in the care of patients with CHF, revealing the non-specificity of the ECG in CHF. Nevertheless a number of CHF/ECG correlates have been proposed and found to be indispensable in clinical practice; they include, among others, the ECG diagnoses of myocardial ischemia and infarction, atrial fibrillation, left ventricular hypertrophy/dilatation, left bundle branch block and intraventricular conduction delays, left atrial abnormality, and QT-interval prolongation. In addition to the above well-known applications of the ECG for patients with CHF, a recently described association of peripheral edema (PERED), sometimes even imperceptible by physical examination, with attenuated ECG potentials, could extend further the diagnostic range of the clinician. These ECG voltage attenuations are of extracardiac mechanism, and impact the amplitude of QRS complexes, P-waves, and T-waves, occasionally resulting also in shortening of the QRS complex and QT interval duration. PERED alleviation, in response to therapy of CHF, reverses all above alterations. These fresh diagnostic insights have potential application in the follow-up of patients with CHF, and in their selection for implantation of cardioverter/defibrillator and/or cardiac resynchronization systems. If sought, PERED-induced ECG changes are abundantly present in the hospital and clinic environments; if their detection and monitoring are incorporated in the clinician's "routine," considerable improvements in the care of patients with CHF may be realized.     

Ablation of Idiopathic Ventricular Tachycardia in Two Separate Regions of the Outflow Tract: Prevalence and Electrocardiographic Characteristics

Few studies have clarified the prevalence and characteristics of idiopathic outflow tachycardia (OT-VT) with an altered QRS morphology after radiofrequency catheter ablation (RFCA), requiring additional RFCA applications at a different portion of the outflow tract (OT) to abolish the OT-VT. Among 344 patients (97 VTs and 247 premature ventricular contractions), 12 (3.5%; VTs-7, PVCs-5; 6 women) had dynamic QRS morphology changes following the RFCA, requiring additional RFCA applications at a different portion to abolish the OT-VT. In 8 of 12 patients (67%), this phenomenon occurred following RFCA at right (RVOT; n = 7) or left ventricular (LVOT; n = 1) endocardial sites of the OT: The second OT-VT was consistently associated with an increase in the R-wave amplitude in the inferior leads, and in five it was finally abolished by RFCA at the left sinus of Valsalva (LSV). Conversely, in four patients (33%), the second OT-VT appeared after RFCA at the LSV: two required additional RFCA applications at the LVOT to abolish the second OT-VT, and one at the RVOT, and all were associated with a decrease in the R-wave amplitude in the inferior leads. This kind of dynamic QRS morphology change was often observed when RFCA was applied to either the first or second OT-VT at a right or left ventricular endocardial site, with the other site being the LSV. A detailed continuous observation of the QRS morphology, especially of the R-wave in the inferior leads, is important for identifying changes in the QRS morphology during RFCA .     

Cardiac Electrodes and Electrograms: Some New Observations and Concerns

Electrode studies have been performed with dead animal tissue and a variety of other materials immersed in saline solution and compared with studies in the canine heart (live and arrested) in an attempt to delineate both normal and anomalous signals sensed by pacemaker electrodes or obtained during diagnostic electrogram recording of cardiac activity. The data from these studies could be useful for defining the origin of artifacts and a variety of other phenomenon such as "fractured" QRS complexes, acute ST segment elevations, His bundle oscillatory signatures, and unexplained potentials synchronously associated with cardiac events. The studies verify that artifacts can be generated in an electrolyte medium by rubbing electrodes against insulators or biologic materials and by inducing motion between common pole materials of an active electrode system. The studies suggest that some of the grasping electrodes in current clinical use may be subject to self-generating artifacts associated with cardiac-induced frictional motion between the constituent materials employed in the electrode design.     

Left ventricular function in patients with ischemic heart disease and "critical" stenosis of one coronary artery. The data from multiphasic ventriculography]

As many as 38 patients with the clinical and angiographic signs of "critical" stenosing of one coronary artery were examined. All the patients underwent coronary angiography and transvenous multiphase left ventriculography. The authors defined a complex of fairly early, "preclinical" signs of myocardial ischemia, pertaining to the energetic effectiveness of the cardiocycle, diastolic function of the left ventricle and indices of the local movement of chamber walls. It is important that these signs are recordable in minimal, clinically undetectable myocardial ischemia characterized by the lack of anginous pain, no changes in the ECG, and when the two-picture analysis, commonly used in clinical practice, provides normal results.     

Functional similarity between electrograms recorded from an implantable cardioverter defibrillator emulator and the surface electrocardiogram

Clinical use of stored electrogram (EGM) configurations currently used in ICDs is limited. The hypothesis that EGMs recorded from electrodes on the ICD surface may improve diagnostic capabilities of the device was tested in the present study. The Buttons on Active Can Emulator (BACE), an ICD-sized device containing four button electrodes, was temporarily placed into a subcutaneous or submuscular left pectoral pocket in 16 patients during ICD implantation. Simultaneous recordings were obtained from the ECG lead II, bipolar EGMs using BACE electrodes, and a bipolar atrial EGM during sinus rhythm (SR), ventricular pacing (VP) at cycle lengths of 500 and 400 ms, and VT. Visible P waves were present in all patients during SR (n = 15), in 5 (33%) of 15 patients during VP, and none of the patients during VT (n = 4) using BACE EGMs and lead II. P and QRS amplitudes and the P:QRS ratio during SR in BACE EGMs were significantly lower than those in lead II. BACE EGMs showed prominent changes in QRS morphology and duration during VP and VT compared to SR, and the magnitude of QRS prolongation during VP was similar to that in lead II. Measurements of PR, QRS, and QT duration during SR showed good agreement between BACE EGMs and lead II. In conclusion, EGMs recorded from electrodes embedded on the ICD housing may potentially improve visual discrimination between supraventricular and ventricular arrhythmias. They also may be useful as a surrogate of the ECG for analysis and monitoring of different components of P-QRS-T complex.     

ECG myogenic artifacts during clonic seizures: a disturbing (and interesting) finding

During motor seizures myogenic artifacts may appear on ECG. We report a patient with recurring convulsive seizures involving left side of his body in whom ECG served as a surrogate of electromyography (EMG), showing myogenic artifacts strongly correlated with clonic jerks. The possibility of standard ECG of recording myogenic potentials when clonic seizures occur is something intriguing, being at the same time both disturbing and informative. In such cases standard ECG works as an EMG, although ECG filter, sensitivity and paper speed is different from EMG currently used in neurophysiological laboratory. However, using standard ECG acquisition parameters, muscular activity may be recorded without excessive attenuation of high-frequency myogenic potentials, permitting to indicate the frequency of clonic movements. On the other hand, whenever possible, positioning of ECG surface electrodes on limbs not (or less) involved in clonic epileptic movements may permit to obtain a sufficiently informative ECG recording with less amount of myogenic artifacts, thus providing essential information on heart rate and rhythm.     

Accuracy of ECG electrode placement by emergency department clinicians

Objectives: Misplaced ECG electrodes can cause changes in ECG recordings, which could have an impact on clinical decisions. We aimed to determine the inter‐rater reliability of ECG electrode placement by senior clinical staff in the ED. Methods: A prospective observational study was conducted in adult patients undergoing an ECG as part of their routine ED care. Adhesive electrodes were left in place after an ECG had been performed by the treating nurse, and subsequently each patient was assessed by two of the three investigators. Each investigator independently recorded the location of the chest electrodes relative to the recommended standard positions. Displacement of the electrodes from the standard positions was measured in the vertical and horizontal planes. The age, sex, weight, height and chest circumference was also recorded. Comparisons were made between investigators to determine variability in assessment of the standard positions. Results: Measurement of horizontal and vertical displacement for each of the six chest leads in the 77 patients resulted in 924 paired measurements. There was substantial inter‐rater variation in the measurement of both vertical (mean 13.5 mm, range 0–105 mm) and horizontal (mean 16.5 mm, range 0–120 mm) displacement. This variation was greater in the lateral chest leads and was more marked in women than in men, especially in the vertical plane (lead V6: men 14.5 mm vs women 27.0 mm, P < 0.01). Conclusion: Among clinical ‘experts’, there is wide variation in the identification of the correct location for electrode placement, particularly in the lateral leads and in women. This has significant implications when comparing ECG in which electrodes have been placed by different clinicians.     

Intracardiac electrode detection of early or subendocardial ischemia

Subendocardial and early transmural ischemia may have significant clinical consequences while manifesting few ECG changes. Catheters were designed to be introduced transvenously into the right ventricle (RV), and coronary sinus (CS) and transarterially into the left ventricle (LV). The intracavitary electrodes were modified so that the electrodes would not contact the endocardium. In twenty-two dogs ninety-eight graded stenoses of the circumflex and left anterior descending coronary arteries were performed while electrograms (EGM) were recorded simultaneously from the intracardiac (IC) electrodes and surface ECG. Of those stenoses resulting in only nonspecific ECG changes, there were specific ischemic changes on 100% of LV, 60% of RV, and 89% of CS electrograms. Of those stenoses which resulted in no ECG change, there were specific ischemic changes in the 9/31 (29%) of LV, 3/31 (10%) of RV, and 6/31 (19%) of CS electrograms. Recognizable patterns of change occur on the intracardiac electrograms in response to both stenosis and reperfusion, earlier than any change on the ECG. Besides being more sensitive, intracardiac electrodes allowed for the detection of ischemia even in the presence of intraventricular conduction defects, strain patterns, and possibly other situations which might otherwise mask ischemic changes on the ECG.     

心肌桥误诊因素分析

目的 :分析有症状心肌桥的临床特点 ,探讨心肌桥误诊原因。方法 :收集 1993- 0 1/2 0 0 0 - 0 5 986例冠状动脉造影中 15例心肌桥病例 ,对比其出入院诊断、ECG与冠状动脉造影结果及临床特点。结果 :心肌桥的初诊误诊率为93.3% ,误诊为冠心病者 1例 ,冠心病稳定型心绞痛者 3例 ,冠心病不稳定型心绞痛者 9例 ,冠心病陈旧下壁心肌梗塞者1例。前降支近中段心肌桥患者 12例 ,前壁缺血占 3/12 ,前侧 下壁缺血占 6 /12 ,侧壁缺血占 1/12 ,下壁缺血占 2 /12。右冠心肌桥患者 3例 ,侧壁缺血占 2 /3,下壁缺血占 1/3。 15例心肌桥患者中有 14例硝酸酯类治疗无效。结论 :心肌桥患者常在中年以后出现酷似冠心病的临床特征及 ECG表现 ,临床确诊的方法是冠状动脉造影。     

Real-time 12-lead high-frequency QRS electrocardiography for enhanced detection of myocardial ischemia and coronary artery disease

Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.     

Electrocardiographic Electrode Misplacement,Misconnection, and Artifact

Background

Electrocardiograms (ECGs) are performed by humans, and thus are subject to human error. An underappreciated source of electrocardiographic abnormality is electrode misconnection, both limb and precordial, and improper placement, which is principally an issue with the precordial electrodes due to anatomic variation. Patterns of abnormality exist; recognition allows the emergency physician to avoid mistaking the resulting electrocardiographic findings for true pathology.

Objectives

The purpose of this clinical review is to describe the patterns of electrocardiographic electrode reversal, misplacement, and artifact and thus make them recognizable to the Emergency Physician.

Discussion

Common limb electrode reversals feature distinctive patterns manifesting as unexpected morphologic and frontal plane axis changes in the QRS complexes in the limb and augmented leads. Precordial electrode misplacement (improper positioning of the electrodes on the chest) is common and may mimic a pseudoinfarction pattern, or ST-segment/T-wave changes, which must be recognized as the result of the misplacement rather than true cardiac ischemia. Precordial electrode reversal should be suspected when the normal R/S wave amplitude transition is violated. Electrocardiographic artifact must be distinguished from dysrhythmia to avoid a potentially hazardous progression to unnecessary diagnostics and therapeutics.

Conclusions

The hallmarks of electrode misconnection, misplacement, and electrocardiographic artifact can be easily mastered by the Emergency Physician; recognition of these findings can positively impact patient care by avoiding unnecessary intervention secondary to misattribution of findings on the 12-lead ECG to cardiac pathology.     

Anodal capture in cardiac resynchronization therapy implications for device programming

INTRODUCTION: Right ventricular (RV) anodal capture (AC) has been reported in cardiac resynchronization therapy (CRT), when left ventricular (LV) pacing uses pseudobipolar (LV tip to RV proximal electrode) configuration. The aim of the study was to analyze the prevalence of AC and its implications for device programming. METHODS AND RESULTS: When AC occurred, the resulting QRS morphology was evaluated with the following pacing modes: (1) LV tip pacing plus RV AC, (2) Biventricular (BiV) pacing (i.e., both LV and RV tip pacing), and (3) BiV pacing plus RV AC. Several interventricular pacing (VV) intervals from 50 ms of LV preactivation to 30 ms of RV preactivation were tested in modes 2 and 3. From 38 consecutive patients, AC was achieved in 14 (in 74% of the pacemakers and in none of the defibrillators). LV tip pacing plus RV AC obtained narrower QRS than BiV pacing at all VV intervals in seven of the patients with AC (50%). When BiV pacing is combined with RV AC, it produced a ventricular depolarization through two wave fronts (one from the LV tip and the second from either the ring or the tip of the RV lead depending on the VV interval programmed). CONCLUSIONS: AC obtained the narrowest QRS of all tested pacing modes in a significant proportion of patients undergoing CRT. Though the stimulus was delivered from three sites (BiV pacing plus RV AC mode), only two wave fronts of ventricular activation were seen by ECG.     

Concentric Remodeling Detection by Magnetocardiography in Patients with Recent Onset Arterial Hypertension

The aim of this work was to evaluate a number of magnetocardiographic (MCG) indices in their predictive ability for left ventricular (LV) concentric remodeling. Twenty-five male patients affected by essential hypertension for no longer than 15 months and presenting signs of LV remodeling participated in the study; 25 normal men volunteers of comparable age were evaluated as controls. All participants underwent echocardiography (ECHO), electrocardiography (ECG), and magnetocardiography (MCG). Several MCG based indices were evaluated, namely the QRS Integral, T Integral, QRS-T Integral, T/QRS Integral, RS Index, and the variations of the electrical cardiac axis (ECA) orientation. MCG indices were compared with ECHO parameters, i.e., left ventricular mass index (LVMI) and relative wall thickness (RWT), and with ECG parameters, i.e., 12-lead standard ECG LVH Sokolow-Lyon and Cornell voltages. QRS Integral values for patients and controls were significantly different (P = 0.03), whereas T Integral values showed only a tendency to differentiate between patients and controls (P = 0.15). No significant correlation between MCG and echocardiographic indices in patients was found; RWT showed a tendency to correlate with QRS Integral (r = 0.34, P = 0.17) and with RS Index (r = 0.49, P = 0.15), and LVMI showed a tendency to correlate with the variations of the ECA orientation (r = 0.38, P = 0.10). Our findings, also supported by preliminary results on patients affected by hypertension induced LV hypertrophy, suggest a potential role of MCG in the evaluation of early electrophysiological alterations due to LV concentric remodeling. (PACE 2004; 27[Pt. I]:709–718)     

Repetitive monomorphic ventricular tachycardia of left coronary cusp origin

Repetitive monomorphic ventricular tachycardia with a morphology of inferior axis and left bundle branch block pattern in patients without structural heart disease commonly originates from the right ventricular outflow tract. We report the case of a 22-year-old man with an incessant, monomorphic ventricular tachycardia with a similar morphology originating from the left coronary cusp, which was confirmed by perfect pace mapping, local ventricular activation preceding the onset of QRS by 25 mse, and eliminated by a single delivery of low-energy (11 W) radiofrequency currents.