Additional electrocardiographic leads in the ED chest pain patient: right ventricular and posterior leads

In the evaluation of the patient with chest pain, the 12-lead electro cardiogram is a less-than-(ECG) perfect indicator of acute myocardial infarction (AMI), particularly when used early in the course of the acute ischemic event; this relative insensitivity for AMI results from many different issues, including a less-than-optimal imaging of certain areas of the heart. It has been suggested that the sensitivity of the 12-lead ECG can be improved if 3 additional body surface leads are used in selected individuals. Acute posterior (PMI) and right ventricular myocardial infarctions are likely to be underdiagnosed, because the standard lead placement of the 12-lead ECG does not allow these areas to be assessed directly. Additional leads frequently used include leads V(8) and V(9), which image the posterior wall of the left ventricle, and lead V(4R), which reflects the status of the right ventricle. The standard ECG coupled with these additional leads constitutes the 15-lead ECG, the most frequently used additional lead ECG in clinical practice. The use of the additional leads might not only confirm the presence of AMI, but also provide a more accurate reflection of the true extent of myocardial damage.     

Estimation of noise level and signal to noise ratio of laplacian electrocardiogram during ventricular depolarization and repolarization

Body surface Laplacian ECG (LECG) has demonstrated its enhanced capability to localize cardiac electrical sources closest to the recording site. The aim of the present study was to evaluate the noise level and signal to noise ratio (SNR) in the LECG as compared to the potential ECG (PECG). Such evaluation is important to determine the applicability of the LECG to localizing and imaging of cardiac electrical activity in an experimental setting. Experimental studies were conducted in six healthy men. A 150-channel PECG was recorded from the anterolateral chest and the LECG was estimated using the finite difference algorithm. The noise level in the PECG and LECG was evaluated using multiple estimation protocols. The signal level during ventricular depolarization and repolarization was also estimated, and the corresponding SNR was calculated. Different filtering techniques were examined to evaluate their effects on the noise level and SNR of the LECG and PECG. The experimental results indicate that with basic signal processing techniques (baseline adjustment, three-point moving average filter, and Wiener spatial filter), the SNR of the LECG is about 30-40% of that of the PECG. Furthermore, the SNR estimated during ventricular depolarization is about three times that obtained during ventricular repolarization for the PECG and LECG. The present study indicates that the LECG derived from the PECG using a local finite difference estimation procedure has satisfactory SNR during the periods of ventricular depolarization and repolarization, and suggests the feasibility of estimating the LECG from the recorded PECG in human subjects in an experimental setting.     

Computer analysis of intraoperative cardiac rhythms using esophageal and surface leads

Esophageal ECG lead and computer as arrhythmia monitor were evaluated in 6 dogs and 23 patients. In dogs arrhythmias were induced by an epinephrine infusion during halothane anesthesia. The computer identified 1858 irregular beats, a cardiologist 2130. Bigeminy was correctly identified 82% of the time, trigeminy 72%, couplets 29%, and ventricular tachycardia 45%. The false positive rate was .03%. In the operating room the monitor identified an average of 44 abnormal beats per patient. In 5 patients junctional rhythm was correctly identified. This study shows the feasibility of using an esophageal ECG lead for computerized ventricular and supraventricular arrhythmia monitoring in the operating room.     

"Peudo" Late Potentials Unmasked by Spectrocardiography

We present a patient with chronic obstructive pulmonary disease and sustained ventricular tachycardia in the setting of unstable coronary artery disease. Signal-averaged ECG (SAECG), inadvertently performed during an atrial tachycardia with 2:1 atrioventricular (AV) block, was abnormal by time-domain analysis, but was normal by a relatively new frequency analysis technique of the entire QRS (spectocardiography). The patient was noninducible for sustained ventricular arrhythmias. Following cardioversion to sinus rhythm. SAECG was normal by time-domain analysis and Spectrocardiography. This technique may show promise in the management of patients who are at risk for sustained ventricular arrhythmias, particularly those who cannot be evaluated by time-domain analysis.     

Prediction of Arrhythmia Risk Based on Signal-Averaged ECG in Postinfarction Patients

In patients surviving acute MI, identification of those at high risk for life-threatening ventricular tachyarrhythmias and/or sudden death is of great importance. Numerous strategies based on indices such as the degree of left ventricular dysfunction, complex ventricular arrhythmias, or parameters of autonomic dysfunction have not yet led to an effective identification of the individual patient at risk. During the past decade, many investigators have recorded low amplitude, high frequency components in the terminal QRS complex (so-called late potentials) from patients prone to sustained ventricular tachycardia. The SAECG has been used to predict life-threatening tachyarrhythmias in patients after acute MI and to screen for inducible ventricular tachycardia in patients with unexplained syncope or sustained ventricular tachycardia. This review article describes the most frequently applied methodology and clinical applications of the SAECG in post-MI patients and discusses the usefulness of noninvasive recordings in various other clinical settings.     

Prevalence of a Brugada Pattern Electrocardiogram in an Urban Population in the United States

Objective: To determine the prevalence of a Brugada-type pattern on routine electrocardiogram (ECG) in an urban population served by a tertiary medical center in the United States.
Methods: The investigators reviewed the ECG database at the Montefiore Medical Center, a tertiary teaching center in the Bronx, New York, over a 10-year period. During this time, 653,006 ECG records in 162,590 patients were identified. The database was queried by applying standard diagnostic criteria in an attempt to identify records with apparent conduction delay and ST abnormality in leads V1–V3. Additional diagnostic criteria were then applied to identify records in an attempt to mimic Brugada-like changes. A cardiac electrophysiologist reviewed records meeting these criteria to confirm the presence of a Brugada-type pattern.
Results: In total, 16,067 patients (9.8%) were identified as having ECGs with right bundle branch block, incomplete right bundle branch block, or RSR' in leads V1 and V2. After applying additional diagnostic criteria evaluating ST segment shift, 456 patients were identified as having a pattern potentially consistent with a Brugada-type ECG. The presence of a Brugada-type pattern was confirmed by physician overread in 20 patients (0.012%).
Conclusion: The Brugada-type ECG pattern is infrequently seen in a large ethnically diverse urban US population. Further evaluation should be considered when this pattern is seen on routine ECG.     

Determinants of the Natural Course of Ventricular Late Potentials After Thrombolytic Therapy for Acute Myocardial Infarction

The intraindividual changes of ventricular late potentials and their possible determinants were examined prospectively in 88 consecutive patients (male: 75; mean age: 58 ± 9 years) after thrombolytic therapy for acute myocardial infarction. Late potential analysis was performed 4 weeks and 12 months after acute myocardial infarction. At the same time, a left heart catheterization was performed to assess the extent of coronary heart disease and left ventricular ejection fraction. The incidence of late potential 4 weeks after acute myocardial infarction was 15% (13/88 patients). Eighteen percent (16/88) of the patients revealed changing results of late potential analysis: 9 patients lost late potential (late potential pos./neg.) 1 year after acute myocardial infarction and 7 patients presented new formation of late potential (late potential neg./pos.). Preserved late potentials were found in four patients (late potential pos./pos.). Late potential analysis remained negative in 68 patients (late potential neg./neg.). There was no influence of age, gender, site of infarction, clinical course, and medical treatment on the natural course of late potential. Changing results of late potential analysis seemed to be correlated with the evolution of left ventricular ejection fraction and the dynamics of coronary heart disease. In the group late potential pos./pos., comparable values for left ventricular ejection fraction were measured at both examinations, whereas late potential neg./neg. had a significant increase in ejection fraction. In the group late potential pos./neg., a significant improvement in left ventricular function was also measured. In contrast, the late potential neg./pos. group tended to have lower left ventricular ejection fractions 1 year after infarction. In the late potential neg./pos. and late potential pos./pos. groups, the extent of coronary artery disease returned to conditions comparable to baseline despite an initial reduction after coronary revascularization performed 4 weeks after infarction. Late potential neg./neg. and late potential pos./neg. revealed a stable benefit gained from coronary revascularization with a persistent reduction in the number of diseased vessels. Dynamic changes in the results of the signal-averaged ECG 1 year after thrombolytic therapy for acute myocardial infarction were observed in 18% of the patients. These changes seem to be correlated with the evolution of left ventricular function and the dynamics of coronary artery disease.     

急性脑血管病131例心电图分析

目的:探讨急性脑血管病心电图改变特点。方法:对131例急性脑血管病病人的心电图检查结果进行统计分析。结果:131例急性脑血管病心电图异常者占77.9%,心电图多表现为ST-T改变达55%,其次为左室肥大和心律失常,心律失常以窦性心动过速,快速房颤,室性早搏二联律,房性早搏多见。结论:急性脑血管病患者心电图异常的程度及变化情况,对病情及预后判断有一定价值,同时对脑卒中患者进行心电方面的检查和监测是很有必要的。     

高血压病的P波改变与左室舒张功能相关性研究

目的：研究高血压病的ＰＩ皮改变与左室舒张功能相关性,为早期估测高血压病的心功能变化提供依据,方法：对８７例高血压患者测量血压、描记标准１ ２导联心电图及进行超声心动图检查,对比Ｐ波指标正常与异常组的其他参数（包括血压、年龄、病程及左室舒张功能等）差异。计算Ｐ波指标与其他参数的相关系数。结果：Ｍａｃｒｕｚ指数、Ｐ波宽度及Ｖ１导联心房终末电势（ＰＴＦＶ１）异常分别为６６％、６０％和４８％,且高血压患者Ａ峰、Ａ／Ｅ比值升高。Ｍａｃｒｕｚ指数和Ｐ波宽度与Ａ峰、Ａ／Ｅ比值和病程正相关,ＰＴＦＶ１与Ａ／Ｅ比值负相关。结论：高血压病的Ｐ波异常是普遍存在的。它反映了左室舒张功能障碍。     

扩张型心肌病患者左室形态结构与五项心电图标准间关系的探讨

对４２例扩张型心肌病患者左室容积指数（ＬＶＶＩ）、室壁厚度（ＬＶＷＴ）及左室重量指数（ＬＶＭＩ）与其诊所左室肥厚（ＬＶＨ）常用五项心电图（ＥＣＧ）标准间的关系进行研究。简单相关分析表明，多数ＥＣＧ标准与ＬＷＩ、ＬＶＷＴ、ＬＶＭＩ呈轻、中度相关；多元逐步回归分析显示：ＬＶＶＩ、ＬＶＭＩ主要与Ｒｏｍｈｉｔ—Ｅｓｔｅｓ记分（ＲＥ记分）、Ｓｏｋｏｌｏｗ和Ｌｙｏｎ指数（ＳＬ指数）有关，ＬＶＷＴ主要与ＳＬ指数有关。     

Variability of Holter electrocardiographic findings in patients fulfilling the noninvasive MADIT criteria. Multicenter Automatic Defibrillator Implantation Trial

In the MADIT study, a selected group of postinfarction patients with asymptomatic nonsustained ventricular tachycardia (NSVT) has been shown to benefit from prophylactic ICD treatment. The present study analyzed the variability of NSVT in a patient population fulfilling the non-invasive MADIT criteria. Three consecutive Holter ECGs were performed in weekly intervals in 68 postinfarction patients with an LVEF < or = 0.35. Patients with NSVT underwent programmed ventricular stimulation (PVS); patients were implanted with an ICD if sustained VT or VF was inducible. If NSVT was found in at least two recordings, the arrhythmia was defined as reproducible. In 28 (41%) of the 68 patients, NSVT was found in at least one recording. Seventeen patients revealed NSVT in the first, the remaining 11 in the second registration; no patient had NSVT only in the third Holter. Of the patients with NSVT, 50% had only one, 39% had two, and 11% had three positive recordings. Thus, reproducible NSVT was found in only 50% of the patients with NSVT. Predictors for reproducibility were LVEF > 0.27, NYHA Class I, absence of digitalis therapy, and > 2 NSVT per 24-hour period. Reproducible NSVT was not associated with risk factors such as elevated mean heart rate, reduced heart rate variability, late potentials, or inducibility of sustained VT during PVS. During 17 +/- 9 months of follow-up, seven (10%) patients experienced arrhythmic events: two without and five with previously documented NSVT. In the latter patients, first occurrence of NSVT was consistently in the first Holter; only two of them had reproducible NSVT. In postinfarction patients, the risk factor NSVT exhibits marked spontaneous variability, especially in those with a low number of NSVT per 24-hour period, LVEF < 0.27 or NYHA III, which limits its clinical value as a selection criterion for PVS. Reproducibility of NSVT itself does not seem to be an independent risk factor.     

Detection of acute myocardial infarction using the 12-lead ECG plus inverted leads versus the 16-lead ECG (with additional posterior and right-sided chest electrodes)

BACKGROUND: The electrocardiographic (ECG) diagnosis of acute myocardial infarction (MI) should be improved. This might be done either by regarding all 24 aspects (both positive and negative leads), or a subset hereof (e.g. 19-lead ECG), of the conventional 12-lead ECG or by using additional electrodes. The purpose of this study was to investigate the accuracy of the different ECG methods in diagnosing acute ST-elevation MI. METHODS: The study population consisted of 479 patients admitted to Lund University Hospital with acute chest pain. One conventional ECG plus leads V4R, V5R, V8 and V9 were recorded for each patient within 24 h of admittance. Biochemical markers were used as the 'gold standard' for diagnosis of MI. We measured ST-segment elevations in the 12-, 16- and 24-lead postadmission ECGs as well as in the 12-, 19- and 24-lead admission ECGs. RESULTS: The sensitivity for detecting acute MI was 28% for the postadmission 12-lead ECG, 33% for the 16-lead ECG and 37% for the 24-lead ECG. The specificities were 97%, 93% and 95%, respectively. For admission ECGs, the sensitivity was 33% for the 12-lead ECG, 45% for the 19-lead ECG and 49% for the 24-lead ECG, with specificities of 97%, 96% and 94%, respectively. CONCLUSIONS: The sensitivity for detecting acute MI was higher for the 16-, 19- and 24-lead ECGs than for the conventional 12-lead ECGs. Their specificity, however, was slightly lower. If increased sensitivity for detecting MI is desired, the 24-lead or 19-lead should be used as no additional electrodes are required.     

Right ventricular infarction: specific requirements of management.

The principal cause of right ventricular infarction is atherosclerotic proximal occlusion of the right coronary artery. Proximal occlusion of this artery leads to electrocardiographically identifiable right-heart ischemia and an increased risk of death in the presence of acute inferior infarction. Clinical recognition begins with the ventricular electrocardiographic manifestations: inferior left ventricular ischemia (ST segment elevation in leads II, III and aVF), with or without accompanying abnormal Q waves and right ventricular ischemia (ST segment elevation in right chest leads V3R through V6R and ST segment depression in anterior leads V2 through V4). Associated findings may include atrial infarction (PR segment displacement, elevation or depression in leads II, III and aVF), symptomatic sinus bradycardia, atrioventricular node block and atrial fibrillation. Hemodynamic effects of right ventricular dysfunction may include failure of the right ventricle to pump sufficient blood through the pulmonary circuit to the left ventricle, with consequent systemic hypotension. Management is directed toward recognition of right ventricular infarction, reperfusion, volume loading, rate and rhythm control, and inotropic support.     

Signal-averaged electrocardiographic parameter progression as a marker of increased electrical instability in two cases with an overt form of arrhythmogenic right ventricular cardiomyopathy

In arrhythmogenic right ventricular cardiomyopathy (ARVC) the fibrofatty substitution of the RV myocardium constitutes the substrate for reentrant circuits, leading to the onset of ventricular arrhythmias. This pathological process also accounts for "delayed ventricular potentials" that could be recorded as late potentials using the signal-averaged ECG technique (SAECG). This study examined two patients affected by overt forms of ARVC who showed a worsening of the electrical instability associated with a fast progression of SAECG parameters, while all the other clinical findings remained unchanged. This suggests a possible role of SAECG parameter progression as a marker of increased electrical instability.     

Low voltage ECG in myocarditis: peripheral edema as a plausible contributing mechanism

A 24-year-old woman was hospitalized with acute myocarditis that led to multiple organ, including heart, failure, with fluid retention. An echocardiogram showed left ventricular ejection fraction approximately 10%, and her electrocardiogram (ECG) revealed low voltage. She rapidly recovered and was discharged 15 days after admission. On evaluation at 1, 10, and 22 weeks after discharge, she was asymptomatic, with unlimited exercise tolerance. An echocardiogram 11 weeks after discharge from the hospital showed left ventricular ejection fraction of approximately 60%. Correlations of weights with ECG QRS voltage parameters in the hospital revealed r = 0.80 and 0.83, with P = 0.021 and 0.029, suggesting that >or=64% of the attenuation of the QRS potentials could be accounted for by the corresponding gain in weight.     

Influence of Filtering Techniques on the Time-Domain Analysis, Diagnosis, and Clinical Use of Signal-Averaged Electrocardiogram

In order to investigate the effect of different filtering techniques on the time-domain analysis of signal-averaged electrocardiogram (SAECG), recordings of 1,192 subjects were analyzed using Butterworth and Del Mar filters, both set at 40–250 Hz high and low pass frequencies. The recordings were taken from six clinically defined groups: (a) survivors of acute myocardial infarction (n = 553); (b) patients with sustained symptomatic postinfarction ventricular tachycardia (n = 89); (c) patients with hyperthropic cardiomyopathy (n = 219); (d) patients with dilated cardiomyopathy (n = 76); (e) direct relatives of patients with dilated cardiomyopathy (n = 170); and (f) normal healthy volunteers (n = 85). The study investigated differences between the SAECG results reported with both filters in three individual aspects: (l) numerical values of individual time-domain SAECG variables; (2) differences in SAECG findings of patients with postinfarction ventricular tachycardia and pair matched patients with uncomplicated follow-up after acute infarction; and (3) the power of SAECG findings to predict high risk of arrhythmic complication (sudden death and/or sustained ventricular tachycardia) among survivors of acute myocardial infarction. Compared with the Butterworth filter, the Del Mar filter led to a systematic difference of + 8% in total QRS duration, was equally powerful in distinguishing between the pair matched patients with and without postinfarction ventricular tachycardia, and was statistically significantly more powerful in identifying those survivors of acute infarction who were at high risk of arrhythmic complications. The study concludes that the use of different filters may produce discordant results of SAECG analysis. Normal and abnormal values for various types of SAEGG recording and analysis have to be established individually for different equipment and different software settings. These optimal cut-offs of SAEGG variables should also take into account the clinical characteristics of patient groups.     

Chronic Ventricular Pacing Using an Output Amplitude of 1.0 Volt

Thirty-seven patients (21 male, 16 female, mean age 71 years) received identical DDD pacemakers. They also received the same bipolar ventricular passive fixation electrode, which has a microporous tip of platinum-iridium, a surface area of 5.8 mm², and steroid elution. Eighteen months after implantation the ventricular charge threshold [μC] was measured telemetrically at 0.5, 1.0, and 2.0 V, respectively. For the 1.0 and 2.0 V amplitudes the pulse duration was increased until the charge per pulse [μC] was twice the threshold value, thus giving a 100% safety margin in terms of charge ("safety charge"). Patients who had ventricular capture at 0.5 V were permanently programmed to 1.0 V (30/37 patients), while those who did not capture at 0.5 V were set to 2.0 V (7/37 patients). In both cases, the pulse duration was programmed according to the rationale of "safety charge." During a routine follow-up period of 6 months, no complications were observed and none of the patients suffered from symptoms indicating loss of ventricular capture. Twenty-four-hour Holter recordings, obtained from all patients at the end of the follow-up with the output parameters unchanged, revealed constant ventricular capture. In patients with chronic stable pacing thresholds and steroid-eluting low threshold leads who have capture at 0.5 V, chronic ventricular pacing at an output amplitude of 1.0 V is feasible, and it seems to be safe if the pacing threshold is measured as charge delivered per pulse and a 100% safety margin in terms of charge is programmed. Reducing the output amplitude to well below the battery voltage may increase pacemaker longevity.     

The Effect of Suppression of the Distortion Artifact during Transcutaneous Pacing on the Shape of the QRS Complex

PROCHACZEK, F., ET AL.: The Effect of Suppression of the Distortion Artifact during Transcutaneous Pacing on the Shape of the QRS Complex. The quality of the ECG recording during transcutaneous pacing was evaluated in six healthy volunteers. The transcutaneous pacing stimulator was an NP4D special unit to which was attached an electronic suppressor of artifact generated by the transcutaneous stimulating impulse. The relationship between this suppression of artifact distortion and the resulting QRS complex was analyzed. The results revealed that the suppression time (described as a 2-mm oscillation from 100-Hz frequency was required for ECG distortion elimination and that this is dependent on the threshold of ventricular pacing. The width of the resulting QRS complex diminishes as the suppression is extended over 110 ms. These results suggest the necessity of individual adjustment of the suppression time so that the efficacy of transcutaneous pacing is adequately assessed.     

DTI对急性心梗患者左室功能动态改变的定量研究

目的：应用多普勒组织成像(DTI)技术定量测定二尖瓣环及梗死节段室壁运动速度，动态观察急性初发前壁心梗患者(AMI)冠状动脉内支架（经桡动脉介入）术后，左室局部及整体功能的改变。方法：经心尖二腔、、四腔、心尖左室长轴三个切面，测定15例正常对照，28例AMI患者的二尖瓣环、左室各壁中段及近心尖段18个位点心肌组织峰值收缩速度（Vs）、舒张早期速度（VE）、舒张晚期速度（VA），观察AMI患者术后1周内、1个月及3个月时心功能恢复情况。结果：反映左室整体功能的二尖瓣环平均VS、VE、VE/VA及局部VS、VE，AMI患者较正常对照组显著减低。无室壁瘤组其梗死节段VS、VE于术后1个月时有恢复，而整体功能术后3个月较1周内明显恢复。而有室壁瘤组局部及整体功能3个月内均无改善。结论：多普勒组织成像技术可定量、精确反映心梗患者局部及整体功能，对鉴别梗死节段心肌存活、预测左室重塑有一定临床价值。