不同高通滤波频率对CRBBB的心室晚电位诊断的初步探讨

完全性右束支传导阻滞(CRBBB)因其心室除极时间延长,本身可导致心电图(ECG)信号的延迟和碎裂,使心室晚电位(VLP)的各项参数增大。因此,使用目前的VLP阳性标准显然不合适,而且在临床VLP研究中发现不同频率的高通滤波,结果亦有差异。本文采用了九种不同的高通滤波频率观察其VLP变化,寻找理想的滤波频率,同时比较国内外常用的阳性诊断标准,初步探讨不同高通滤波频率对CRBBB检出VLP的诊断标准。     

不同带通滤波对于心室晚电位检测结果的影响（摘要）

晚近,不同带通滤波(滤波)对于心室晚电位(VLP)的影响,受到重视。为了进一步阐明其意义,我们采用三种滤波对于 VLP 阴性正常人和阳性病人体表信号叠加心电图(SAECG)作了分析,现报告如下。对象和方法 30例 VLP 阴性(简称正常组)均系经体检属健康的医科大学生。60例VLP 阳性(简称病例组)系本院门诊和住院病人。不同滤波 VLP 判定指标见表1,凡符合其中两项者判为 VLP 阳性。     

信号平均心电图正常值分析(摘要)

<正> 作者对220例正常人进行了体表信号平均心电图(SAECG)检测,以了解其正常范围不同滤波频率对各参数的影响,为心室晚电位(VLP)阳性诊断标准提供依据。经询问病史,体检以及X线胸片、心电图、心向量图等检查,排除了心、肺及其他重要器官疾患,部分人还进行了超声心动图、平板运动试验等检盘。年龄20～82岁,男110例,平均49.5岁;女110例,平均48.4岁。采用美国Marguette electronics公司MAC-15心脏工作站。噪声水平≤0.5,≥0.3μV。心电信号采用Simson倡导的X、Y、Z双极正交导联和双向高通滤波,滤波频率25～250Hz及40～250Hz,在窦性心律下进行200次心动周期的叠加。观察指标主要为:(1)综合导联滤波的QRS总时间     

急性心肌梗塞静脉内链激酶减少心室晚电位的发生

作者报告115例急性心肌梗塞(AMI)患者,55例静脉内链激酶(SK)治疗(SK组),60例保守治疗(非SK组)。行冠状动脉造影术SK组45例(81.8%);非SK组21例(35%),使用双极正交X、Y、Z导联,滤波、两向高频通滤波在25Hz和40Hz。分析结果选择两个滤波频率,最佳通滤波频率时记录心室晚电位(VLP).ECG信号平均结果无异时决定施行冠状动脉造影术,患者常有心绞痛或活动平板试验诱发局部缺血。残存狭窄程度按照TIMI(心肌梗塞血栓溶解)等级指标试验研究,血栓溶解血管Ⅱ(?)或Ⅲ(?)列为“开放”.     

高带通滤波对心室晚电位诊断标准的影响

通过用25～250Hz、40～250Hz、80-250Hz 三种不同的高带通双向数字滤波体表信号平均方法,定量分析正常人和有症状的室速患者的心室晚电位表明:随着高带通滤波频率的升高,HFRWS 减小,HFQRSD 缩短,HFLAD 有延长的改变;不同的高带通滤波对心室晚电位的诊断标准有一定影响。25Hz 有较高的特异性,而80Hz 有较好的敏感性。不同的心室晚电位诊断标准有不同的敏感性和特异性。当25Hz,HFRMS₄₀≤25uV,HFQRSD≥120ms,HFLAD≥40ms;当40Hz 时,HFRMS₄₀≤20uV,HFQRSD≥120ms,HFLAD≥40ms;当80Hz 时,HFRMS₄₀≤15uV,HFQRSD≥110ms,HFLAD≥50ms 时均能较好地区分正常组和室速组。     

心室晚电位、心率变异对急性心肌梗死患者心律失常事件发生的预测价值

目的 了解心率变异(HRV)、心室晚电位(VLP)在预测急性心肌梗死(AMI)预后的价值。方法 40例AMI患者HRV(SDNN)、VLP测定,与40例正常人进行对比分析。结果 AMI组SDNN(87.9±25.07ms)与对照组(13.37±35.96ms)比较明显减低(P<0.001),AMI组VLP阳性(11例)与正常组(1例)比较明显增高(P<0.01)。梗塞患者室性心律失常事件组与非事件组HRV(SDNN)、VLP比较相差显著(P<0.005)。对心律失常事件发生预测方面,HRV特异性为93.55％,相对危险性为10.50,VLP敏感性为44.4％。二者结合特异性、相对危险性增加。结论 二项指标均有独立的预测价值,如同时检测可望提高阳性预测值。     

心室晚电位的频谱分析

用体表叠加平均心电图(SAECG)记录分析系统对115例正常人和116例冠心病心肌梗塞(MI)患者作SAECG 记录并进行心室晚电位(VLP)及频谱分析,发现 MI 患者 VLP 阳性率为37.30%;正常人 SAECG 频谱的高频成份(20—150Hz)明显低于 MI 患者(P<0.01),低频成份(0—20Hz)明显高于 MI 患者(P<0.01)。提示 MI 患者可能发生 VLP,其频率结构中高频成份明显增多。     

心室晚电位对冠状动脉搭桥术后室性心律失常的预测

目的 研究冠状动脉搭桥术前后心室晚电位(VLP)的变化，评价术前VLP阳性对术后发生室性心律失常的预测价值。方法 采取冠状动脉搭桥术患者40例。其中心肌梗塞(M1)病史组31例，无MI病史组9例。室壁瘤组7例，非室壁瘤组33例。观测冠状动脉搭桥术前及术后2周VLP的变化。结果 1．MI及室壁瘤患者术前FQRS显著高于，LAS显著低于非MI及非室壁瘤患者(P<0．05)；VLP阳性率高于非MI及非室壁瘤患者。2．术后VLP阳性率显著低于术前(P=0．025)，VLP转阴率为75％。3．术前VLP阳性患者术后发生室性心律失常例数显著高于术前VLP阴性患者(P=0．03)。结论：1．M1及室壁榴患者VLP阳性率高提示其存在折返性室性心律失常的电生理基础。2．冠状动脉搭桥及室壁瘤切除术后VLP转阴提示外科手术不仅能够改善梗塞区域局部心肌的血供，而且切断了潜在的折近径路，从而减少了VLP及室性心律失常的发生。3．术前VLP阳性是预测术后室性心律失常的独立指标(敏感性71．43％，特异性78．79％，阳性准确率41．67％，阴性准确率92．86％)，据此指导临床预防应用抗心律失常药物。     

心室晚电位心率变异对急性心肌梗死者心律失常事件发生的预测价值

目的 通过40例急性心肌梗死(AMI,A组)者的心室晚电位(VLP)、心率变异(HRV)检测,与40例正常人(B组)进行对比。结果 A组HRV(SDNN)较B组明显缩小(P<0.001),VLP阳性率明显增加(P<0.01)。室性心律失常(VT)事件组(A_1组)与非事件组(A_2组)的2项指标比较有非常显著差异(P<0.005)并且HRV特异性增高。结论 2者同时监测可增加预测指标的特异性、有效性及相对危险性,临床意义更大。     

频域法检测体表心室晚电位的参数选择

采用ART-1200EPX型检测仪的FFT_3软件,对60例正常人和56例器质性心脏病时域法(TDA)心室晚电位(VLP)阳性患者的检测结果作了分析。旨在探讨频域法(FDA)检测VLP 主要参数的合理选择。结果表明:(1)选择滤波后综合QRS 波(composite)、Blackman-Harris 窗和120ms 分析段检测时,以振幅谱面积比(AAR)作为观察指标比较合理,(2)采用20-50Hz/10-50Hz 计算AAR 较佳,(3)在上述条件下,初步提出FDA 的VLP 正常值范围≤3327。     

Optimal bandpass filters for time-domain analysis of the signal-averaged electrocardiogram

The optimal bandpass filter for signal averaging of the surface QRS complex to detect late potentials is undefined. A study was conducted in 87 patients; 25 (mean age 34 +/- 10 years) were normal (group I), 29 (60 +/- 20 years) had organic heart disease without ventricular tachycardia (group II) and 33 (62 +/- 15 years) had sustained ventricular tachycardia (group III). In all patients signal-averaged electrocardiography (200 beats) was performed using a sharp, bidirectional filter and data analyzed using the following 7 high-pass filter settings: 10, 15, 20, 25, 40, 80 and 100 Hz. For each filter the duration of the signal-averaged QRS complex, the low-amplitude signals of less than 40 microV and the root-mean-square voltage of the terminal 40 ms (RMS-40) were determined. Normal values for each filter were determined from group I patients. In all 3 groups, quantitative signal-averaged variables were filter dependent. There was a progressive and marked decrease in RMS-40 and a progressive and marked increase in low-amplitude signal duration as the high-pass filtering was increased from 10 to 100 Hz. In contrast, high-pass, filter-dependent changes in signal-averaged QRS duration were less marked. The sensitivity and specificity for each filter using RMS-40 as the index of late potentials in separating group III patients from group II patients were: 10 Hz-64% and 52%; 15 Hz-57% and 72%; 20 Hz-57% and 76%; 25 Hz-42% and 90%; 40 Hz-61% and 83%; 80 Hz-88% and 69%; and 100 Hz-79% and 62%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prognostic significance of programmed ventricular stimulation in the noninvasive registration of ventricular late potentials in the postinfarct period

The prognostic significance of programmed ventricular stimulation for assessing ventricular vulnerability and of signal averaging for detection of ventricular late potentials was assessed prospectively in 132 survivors of acute myocardial infarction. The median day of these studies was the 22nd. Programmed ventricular stimulation (PVS) included single and double premature stimuli during sinus rhythm and paced ventricular rhythms at rates of 120, 140, 160 and 180 bpm. The endpoint for stimulation was the induction of 4 or more consecutive echo beats. 59 of 132 patients (45%) had late potentials in their body surface signal-averaged ECG. The prevalence was 35% in those with anterior wall infarction and 54% in those with inferior wall infarction (chi 2 = 3.9; p less than 0.05). In 61 patients (46%), 4 or more consecutive echo beats were induced. In 28 of these patients, sustained ventricular tachycardia or fibrillation were initiated. During follow-up (15 +/- 11 months; mean +/- S.D.), there were 4 sudden deaths. Neither PVS nor signal averaging were able to predict these events. Spontaneous symptomatic sustained ventricular tachycardia occurred in a total of 9 patients, all of whom had an abnormal PVS result (sensitivity 100%); 7 of these patients also had late potentials (sensitivity 78%). Stepwise analysis revealed that the combination of late potentials (duration greater than or equal to 40 ms), and of induction of sustained ventricular tachycardia at rates less than 270 bpm had the highest predictive value (50%). In contrast, the prevalence of sustained ventricular tachycardia was as low as 3% in those without late potentials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recording of abnormal late ventricular activity by high-resolution magnetocardiography

High-resolution magnetocardiography (HR-MCG) is a new noninvasive technique for detection of very low-amplitude magnetic fields generated by the electric activity of the heart. We studied 11 patients with documented sustained ventricular tachycardia after myocardial infarction (VT group), 11 patients with old myocardial infarction without ventricular tachycardia (MI group) and 11 normal controls (N group) with HR-MCG and high-resolution electrocardiography (HR-ECG). After averaging and high-pass filtering (25 Hz, 40 Hz, 60 Hz and 80 Hz) the XYZ leads of HR-ECG were combined to vector magnitude and the magnetic recordings from 3 × 3 grid locations were enveloped with Hilbert transformation. Then the QRS duration and the root-mean-square (RMS) amplitude of the last 40 ms, 50 ms and 60 ms of the QRS were calculated. The QRS duration was significantly longer in the VT group compared to the MI and the N group both in HR-MCG and HR-ECG. Also the RMS values were clearly smaller in the VT group with both methods. There were no significant differencies in the diagnostic power of these two methods. The 25 Hz high-pass filtering separated best the VT group from the MI group and the N group. In conclusion HR-MCG is a new non-invasive method for identification of patients at risk of malignant ventricular arrhythmias after myocardial infarction.Abbreviations HR-ECG high-resolution electrocardiography - HR-MCG high-resolution magnetocardiography - LAS low amplitude signal - LF late fields - LP late potentials - MI myocardial infarction - RMS root-mean-square - VT ventricular tachycardia     

Independent value of signal-averaged electrocardiography and left ventricular function in identifying patients with sustained ventricular tachycardia with coronary artery disease

To determine if the signal-averaged electrocardiographic detection of late potentials is an independent marker of sustained ventricular tachycardia (VT) in patients with documented chronic coronary artery disease (CAD), 57 patients underwent signal-averaged electrocardiography. Mean ejection fraction was 47 +/- 13% in the 14 patients with sustained VT and 56 +/- 19% in the 43 patients without VT (difference not significant). The sensitivity, specificity and accuracy of late potentials for detecting patients with VT were 64% (9 of 14), 79% (34 of 43), and 75% (43 of 57), respectively. Univariate analysis and stepwise logistic regression of angiographic and electrocardiographic variables identified late potentials as an independent marker of the patient with sustained VT. The odds ratio for late potentials to detect patients with prior sustained VT was 2.6. Six-month follow-up revealed a cardiac mortality rate of 11% and an arrhythmia event rate of 22% in patients with late potentials vs a cardiac mortality rate of 3% and an arrhythmia event rate of 13% in patients without late potentials. Thus, signal-averaged electrocardiographic detection of late potentials is useful in identifying patients with prior sustained VT independent of left ventricular function.     

Behavior of ventricular late potentials following catheter ablation of ventricular tachycardia

In 10 patients non-invasively recorded signal-averaged electrocardiograms were obtained before and after direct-current ablation of ventricular tachycardia (right ventricular origin n = 5; left ventricular origin n = 5). The algorithms proposed by Simson and Karbenn et al. were used (modified Frank leads, high-pass filter cut-off frequency 25 Hz). No differences were observed between the mean values of the duration of the QRS-complex, the mean voltage during the last 40 ms of the QRS-complex, the duration of the late potentials and the number of patients having late potentials before and after ablation, respectively. The success of ablation could not be predicted by the signal-averaged ECG. There was no difference between the averaging parameters of those patients without recurrences of ventricular tachycardia during the follow-up period and those with (n = 3). Thus, the signal-averaged ECG did not prove helpful in predicting a successful outcome of direct-current catheter ablation of ventricular tachycardia.     

Late potentials in idiopathic dilated cardiomyopathy

Twenty-five patients with idiopathic dilated cardiomiopathy were investigated in order to evaluate the role of late ventricular potentials as possible markers of ventricular tachycardia or sudden cardiac death. Holter monitoring showed ventricular tachycardia in 9 patients (group A) all of whom had late ventricular potentials, (mean +/- SD length 37.22 +/- 15.83 ms and mean +/- SD voltage 5.62 +/- 2.78 microV). Mean +/- SD ejection fraction in this group was 20 +/- 9.39%. In 16 patients (group B), without ventricular tachycardia, means +/- SD ejection fraction 27.5 +/- 8.17%; late ventricular potentials were recorded in 2 patients. During the follow-up period (means +/- SD 11.53 +/- 7.19 months), 3 patients underwent heart transplantation, 2 patients underwent pace-maker implantation and 2 patients from the ventricular tachycardia group died one from sudden cardiac death and the other from progressive heart failure. No significant differences were found in the ejection fraction either between the ventricular tachycardia and the non-ventricular tachycardia group, or between the late ventricular potentials and the non-late ventricular potential groups. Negative data were also obtained when we tried to find a correlation between the ejection fraction and late ventricular potential length and/or voltage. Good results were observed with regard to sensitivity (100%), specificity (87%) and predictive accuracy (81%) but follow-up data did not specify a definite prognostic value for late ventricular potentials. The Authors conclude that late ventricular potentials are markers of patients with idiopathic dilated cardiomyopathy who are prone to ventricular tachycardia. However, the role of late ventricular potentials in sudden cardiac death is still uncertain.     

Comparison of frequency and time domain analysis of the signal-averaged electrocardiogram in patients with ventricular tachycardia and coronary artery disease: methodologic validation and clinical relevance

Frequency analysis with fast Fourier transform and time domain analysis after signal averaging of the electrocardiogram (ECG) have given contradictory results in patients with sustained ventricular tachycardia after myocardial infarction. Therefore, the same orthogonal ECGs were analyzed in the frequency domain (Blackman-Harris window) and the time domain after signal averaging and high gain, low noise amplification (0 to 300 Hz) in 30 patients with sustained ventricular tachycardia after myocardial infarction, 15 patients without ventricular tachycardia after infarction and 15 healthy subjects. Patients with bundle branch block were not excluded. Twenty-one of the 30 patients with ventricular tachycardia had late potentials in the time domain and abnormal Fourier transform of the ST segment (defined as increased spectral area of 60 to 120 Hz and spectral peaks greater than 10 dB). Among the remaining nine patients with ventricular tachycardia all had no late potentials in the time domain and one manifested abnormal frequency spectra. In contrast, of the 15 patients without ventricular tachycardia after infarction, 2 had late potentials in the time domain and only 1 demonstrated abnormal frequency spectra; none of the healthy subjects manifested either phenomenon. Patients with bundle branch block were correctly classified by Fourier analysis, but were frequently missed by time domain analysis. Normalization of the spectra and area ratio proved potential pitfalls, and the choice of an appropriate ST segment was crucial: if the segment was long with respect to the duration of the late potentials and if it extended too far into the QRS complex, fast Fourier transform yielded random results.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diagnostic value of electrocardiographic variables to predict the presence of ventricular late potentials

To test the hypothesis that the presence of ventricular late potentials in the highly amplified, averaged and filtered surface electrocardiogram (ECG) can be predicted from the conventional surface ECG, 211 patients with and without previously documented sustained ventricular tachycardia outside the acute phase of myocardial infarction were studied. The presence of left ventricular akinesia or aneurysm was significantly correlated with the ECG score (based on Q wave duration, R wave duration and amplitude ratio). The mean ECG score in patients without ventricular tachycardia was 3.4 +/- 3.5 points compared with 5.5 +/- 3.9 points (p less than 0.001) in patients with ventricular tachycardia. The presence of late potentials was positively correlated with the ECG score in the whole cohort of patients. This was also the case in the subgroup of patients without a history of sustained ventricular tachycardia. In contrast, in patients with ventricular tachycardia, the presence of late potentials was independent of their ECG score. Using linear discriminant function analyses to predict the presence of late potentials, a history of ventricular tachycardia alone and the ECG score alone had a high predictive power (high standardized coefficients). If combinations of variables were analyzed including estimates of left ventricular function (presence of aneurysm or akinesia; ejection fraction), the ECG score and a history of ventricular tachycardia still ranked highest. The influence of ejection fraction if used in combination with other variables for the prediction of late potentials was relatively small (standardized coefficient of 0.4). In conclusion, the surface ECG can be used in patients previously free of sustained ventricular tachycardia to predict the presence of ventricular late potentials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Late potentials on the signal-averaged electrocardiogram after canine myocardial infarction: correlation with induced ventricular arrhythmias during the healing phase

Signal-averaged electrocardiograms (ECGs) and programmed ventricular stimulation were serially performed in 12 dogs (3 weeks of age) after experimental anteroapical myocardial infarction. At electrophysiologic study, sustained ventricular tachyarrhythmia was induced in seven dogs on at least one occasion. Of a total of 39 electrophysiologic studies, sustained monomorphic ventricular tachycardia was induced in seven studies and ventricular fibrillation in eight studies. In the remaining studies, no ventricular arrhythmia could be induced with triple ventricular extrastimuli. There was considerable day to day variability in the response to programmed stimulation and the results of the signal-averaged ECG. The signal-averaged QRS complex was significantly longer in dogs with inducible ventricular tachycardia or fibrillation (61 +/- 5 versus 57 +/- 3 ms, p = 0.02), had a lower terminal QRS amplitude (24 +/- 20 versus 46 +/- 33 microV, p = 0.04) and a longer late potential duration (19 +/- 4 versus 15 +/- 3 ms, p = 0.003) compared with that in animals with no inducible ventricular arrhythmia. Late potentials were defined as a total QRS duration greater than 58 ms, a terminal QRS amplitude less than 20 microV and a late potential duration greater than 18 ms. Using this definition, late potentials were seen in two distinct phases--immediately after coronary ligation and then beyond the first 72 h after infarction. The appearance of late potentials coincided with a change in arrhythmia inducibility from no ventricular arrhythmia to initiation of sustained monomorphic ventricular tachycardia. There is a close relation between inducibility of ventricular tachycardia in experimental canine myocardial infarction and the appearance of late potentials on the surface ECG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arrhythmogenic potential of cardiomyopathies. Dilated cardiomyopathies

Sixty-nine cases of non-ischemic dilated cardiomyopathy were studied prospectively from February 1983 to February 1989 (52 men: 53 +/- 13.5 years of age). There were 6 cases of sustained ventricular tachycardia. Thirty-seven patients were in Class III or IV of the NYHA Classification. In addition to echocardiography, radionuclide studies, cardiac catheterisation and coronary angiography, they all underwent 24 hour Holter monitoring, signal-averaged electrocardiography and, in 46 cases, endocavitary electrophysiological investigations. Holter monitoring showed ventricular extrasystoles greater than or equal to Grade 3 of Lown's classification in 72% of patients (26% had nonsustained ventricular tachycardia) and these patients had a significantly lower cardiac index. Twenty five per cent of patients had late ventricular potentials (versus 2% in 50 normal subjects; p less than 0.02); this proportion rose to 32% in those patients with greater than or equal to Grade 3 ventricular extrasystoles and to 66% in the patients with spontaneous ventricular tachycardia; the cardiac index was lower in patients with late ventricular potentials (2.3 vs 2.8 l/min/m2; p less than 0.01) and they had a higher incidence of greater than or equal to Grade 3 ventricular extrasystoles (94% vs 65% in patients without late ventricular potentials, p less than 0.05). Programmed ventricular stimulation induced sustained or nonsustained monomorphic ventricular tachycardia and ventricular fibrillation in 15% of cases. The 6 cases of induced sustained ventricular tachycardia were only observed in the 6 patients with spontaneous sustained ventricular tachycardia and they had the same electrocardiographic appearances.(ABSTRACT TRUNCATED AT 250 WORDS)