Quantitative analysis of ventricular late potentials (LP) in healthy subjects. Comparative study with Holter monitoring.

Signal averaging is a technique that improves the signal-to-noise ratio. It allows the detection of low-amplitude wave formes in the terminal portion of the QRS complex, also known as ventricular late potentials. A high incidence of arrhythmic events is found in patients with abnormal ventricular late potentials after an acute myocardial infarction. Few wide studies have been conducted in healthy subjects to assess normal values. One hundred sixty-five healthy subjects are enrolled in our study (59 men and 106 women). The results (mean +/- standard deviation) are as follows: duration of filtered QRS: 89.5 +/- 9.1 ms; duration of the low-amplitude signals in the terminal portion of QRS < 40 microV: 27.1 +/- 7.8 ms; root-mean-square voltage in the last 40 ms: 47.2 +/- 29.5 microV. A signal difference is noted between men and women for the QRS duration. No difference is found in HFD40 and RMS40. QRS duration confidence limits of 95% are < 108 ms for the total group. HFD40 and RMS40 confidence limits of 95% are respectively of 43 ms and 13 microV. There is no significant difference of the values for age. There is no relation between the severity of a ventricular arrhythmia and the values of the three parameters of the late potentials in a healthy subjects population.     

正常人和冠心病人体表心室晚电位的定量分析

本文定量分析正常人(220例)和有室性心动过速(VT)和(或)室颤(VF)史的冠心病人(32例)的体表心室晚电位(VLP)．讨论了正常人不同滤波条件下的VLP正常值。根据不同高通滤波频率后VLP各参数的敏感性及特异性的研究,表明40Hz高通滤波后其敏感性(66％)、特异性(96％)相对较高．提示40～250Hz为技合适的滤波频率．VLP预测持续性VT的价值较大。     

Spectrotemporal analysis of ventricular late potentials

The authors introduce a new technique for the analysis of ventricular late potentials: spectrotemporal mapping. Spectrotemporal mapping displays a signal in both the time and frequency domains simultaneously, overcoming some of the limitations of single domain analysis. Spectrotemporal analysis of late potentials was developed from a critique of classical spectral analysis methods. Several examples of spectrotemporal analysis of signal-averaged ECG waveforms are presented. These include cases in which spectrotemporal mapping was able to represent late potentials that were not seen after conventional time-domain processing. Spectrotemporal mapping reveals that ventricular late potentials have a time-varying energy spectrum, which theoretically would preclude the use of classical Fourier analysis techniques. Both the vector magnitude and Fourier transformations are a reduced representation of the information available in the signal average. Spectrotemporal mapping combines time and frequency information in a way that is compatible with the basic statistical structure of late potentials.     

Ventricular late potentials in normal subjects

Low-amplitude late potentials detected in the terminal part of ventricular activation have been evaluated as a possible means of identifying patients prone to sustained ventricular tachyarrhythmias. These signals are usually absent in those without such arrhythmias and in normal subjects. 67 healthy subjects, with no suggestion of cardiac disease from examination or electrocardiograms, were studied in an effort to report the incidence of late potentials in normal subjects. Three subjects met the criteria for abnormal late potentials (4%); the vectormagnitude complexes of these subjects were indistinguishable from those seen in patients with spontaneous sustained ventricular tachycardia after myocardial infarction. Measured indices from our subjects were compared with those of normal subjects studied by other investigators utilizing similar analytic techniques and similar software and equipment. Explanations are considered for the occurrence of false-positives. It is concluded that the incidence of late potentials in normal subjects is very low and thought to represent some type of false-positive expression related either to the recording or analytic technique. However, in certain instances, the occurrence of late potentials in a seemingly normal person may be a predictor of underlying structural pathology.     

Diagnostic significance of late ventricular potentials

A study using two methods of noninvasive registration of ventricular late potentials (VLP), computer averaging and beat-to-beat spatial averaging, was conducted in 27 patients with ventricular tachycardia and 11 healthy volunteers. Both techniques are described in detail. The duration of QRS complex on high resolution ECG was found to be significantly longer in patients with VLP as compared to those of patients without VLP and having ventricular tachycardia as well as healthy adults. The data obtained by both methods do not differ significantly. The beat-to-beat method was not informative in about 20% of cases because of the ineffective filtering procedure and the presence of myographic noise on the amplified CS. The duration of VLP was 44 +/- 20 ms in patients with documented ventricular tachycardia. The sensitivity of the assessment of arrhythmogenic ventricular activity was 70% with the computer method, and 59% with the beat-to-beat spatial averaging technique. The specificity and predictive value of both registration methods were 100%.     

Significance of late ventricular potentials in myotonic dystrophy

In 39 patients with myotonic dystrophy, we found a high percentage of infrahissian cardiac conduction abnormalities (51%) and late potentials (46%), whereas spontaneous and inducible ventricular arrhythmias were rare. These results suggest that the prolongation of QRSD and the duration of the low-amplitude signal on the signal-averaged electrocardiogram were related to delayed activation of the His and Purkinje tissue rather than true late potentials.     

Spatial domain analysis of late ventricular potentials. Intraoperative and thoracic correlations

For investigation of late potentials seen on the signal-averaged electrocardiogram, intracardiac and thoracic distributions of terminal activity were analyzed in 16 patients undergoing cryosurgery for ventricular tachycardia after remote myocardial infarction. The body surface potentials measured with 63 time-averaged unipolar leads were compared with epicardial and endocardial potential maps in six patients without and 10 patients with bundle-branch block. Intracardiac post-QRS activity, defined as extending beyond the thoracic QRS offset, was found in five of six patients without bundle-branch block (83%) and in five of 10 patients with bundle-branch block (50%), corresponding to 4 +/- 5% of the total number of electrograms in each patient. Fragmentation, double deflections, and single deflections were observed in 27%, 34%, and 39%, respectively, of these post-QRS electrograms. Post-QRS activation patterns that were stable from beat to beat showed slow propagation around or within areas of conduction block. Post-QRS activity was most often observed on both epicardial and endocardial surfaces (five of 10 patients). In the six patients without post-QRS activity, an area of late activity displaying low-amplitude deflections that were masked by the terminal activation of the normal myocardium was identified. Isopotential maps of the high-pass-filtered (55-Hz) thoracic and intracardiac signals demonstrated a close spatial correlation between the location, amplitude, and orientation of the potential extrema observed over the thoracic, epicardial, or endocardial surfaces during post-QRS activity. The thoracic patterns were generally dipolar with close extrema for anteroseptal or apical sites of post-QRS activity and more distant extrema for other sites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hypertensive cardiopathy and ventricular late potentials]

Ventricular arrhythmias occur with increased frequency in hypertensive patients with left ventricular hypertrophy (LVH). The aim of this work is to study the incidence of ventricular late potentials (LP) and their relation to ventricular arrhythmias in 148 hypertensive patients, 87 men and 55 women, without evidence of a coronaropathy. For each patient we carried out a signal-averaged electrocardiography, an echocardiogram to determine the LV mass index (LVMI) and the LV end-diastolic dimension (EDD), and 24 hours Holter monitoring to record ventricular arrhythmias filed according to Lown's classification. LP were considered present if the root-mean-square voltage during the last 40 ms of the QRS was: < 20 uV in absence of bundle branch block, or < or = 17 uV in presence of bundle branch block. [table: see text] The frequency of LP appears exceptional in hypertensive patients without LVH (5%) and remains uncommon in patients with concentric LVH (13%). The incidence of LP is only frequent at the end stage of hypertensive cardiopathy with eccentric LVH (48%). The severity of ventricular arrhythmias is only correlated to the presence of LP in patients with concentric LVH (p < 0.02).     

Effects of non-pharmacological interventions on ventricular late potentials

The purpose of the paper is to review the presently available information of the effects of non-pharmacological interventions for the control of drug-refractory ventricular tachyarrhythmias on non-invasively recorded ventricular late potentials. During recent years, non-pharmacological interventions have evolved as an alternative form of treatment to control drug-refractory ventricular tachyarrhythmias. The effects of these non-pharmacological measures on ventricular late potentials are poorly understood. Successful surgical control of ventricular tachycardia often normalizes the signal averaged ECG and may eliminate delayed potentials. Thus, this non-invasive test may be useful in assessing surgical efficacy in subgroups of patients with ventricular tachycardia. However, the clinical value of late potentials in assessing surgical efficacy in the individual case may be limited as the sensitivity and specificity of the loss of late potentials after antitachycardia surgery are low. In addition, the effects of transvenous catheter ablation on ventricular late potentials will be reviewed. The available information suggests that this intervention has little effects on the presence or absence of late potentials. Thus, non-invasive recording of late potentials seems not to be helpful in predicting the acute and long-term efficacy of catheter ablation. In conclusion, changing of the parameters in the signal-averaged QRS complex after antitachycardia surgery may be useful in predicting the efficacy of surgical interventions for drug-refractory ventricular tachycardias in subgroups of patients. However, the sensitivity and predictive accuracy of this test are low, thus limiting its clinical usefulness.     

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.     

Complex ventricular arrhythmia in apparently healthy young subjects

The aim of this study of 20 young subjects (28 +/- 10.6 years) with no apparent cardiac disease on clinical examination and chest X-ray was to determine the origin of complex ventricular arrhythmias: monomorphic or polymorphic ventricular extrasystoles, isolated or in valves (average 18 158 +/- 12 388 per 24 hours) and/or ventricular tachycardia (5 cases, sustained in 3). These arrhythmias were aggravated (N = 6), disappeared (N = 8) or remained unchanged (N = 5) during exercise. The inter-critical ECG showed ST changes in 5 cases. The extrasystoles had a left bundle branch block configuration in 14 cases and a right bundle branch block configuration in 9 cases. Nine patients were Grade 2 (45%) and 11 patients Grade 4B of Lown's classification. Complementary investigations (echocardiography), radionuclide investigations, right and left heart catheterisation, selective right and left ventriculography and coronary angiography) showed a high incidence of arrhythmogenic right ventricular dysplasia (N - 14) associated with left ventricular abnormalities in 13 cases: hypofixation of Thallium (N = 14) associated with left ventricular abnormalities in 13 cases: hypofixation of Thallium (N = 11), abnormal global left ventricular function (N = 13) with decreased ejection fractions in half the cases, left ventricular dilatation in a third of cases (average and diastolic volume: 109.8 ml/m2), mean velocity of circumferential fibre shortening decreased in 86% of cases (average 0.88 cir/sec), angiographic abnormalities of segmental left ventricular wall motion in 36% of cases; 2 clinically silent cases of mitral valve prolapse were associated with these left ventricular changes; these cases represent forms of arrhythmogenic cardiac disease localised to the right ventricle or involving both ventricles which should be searched for routinely in young patients with apparently normal hearts but with idiopathic and severe ventricular arrhythmias. The diagnosis can only be established by angiography. In other cases, isolated left ventricular abnormalities are detected: two cases of hypertrophic non obstructive cardiomyopathy including one apical form, a condition which may be suspected from analysis of the surface ECG and careful 2D echocardiographic study; phonomechanography may be normal; one idiopathic left ventricular aneurysm which was only diagnosed at ventriculography; one dilated cardiomyopathy affecting the left ventricle. In our series, none of the patients had coronary artery disease and two patients even had no abnormality of any of these investigations.(ABSTRACT TRUNCATED AT 400 WORDS)     

餐后无症状性心肌缺血患者的心室晚电位临床分析

目的通过检测餐后无症状性心肌缺血(silent myocardial ischemia,SMI)患者心室晚电位(ventricular late potentials,VLP)以评价其发生心肌梗死或猝死的危险性。方法对56例有餐后SMI的患者作为观察组,在生活指导前后分别于空腹、餐后2小时和运动后进行VLP检查,并与对照组同期非餐后SMI的223例患者进行对比。结果生活指导前,观察组于空腹、餐后2小时和运动后的VLP阳性率均分别为25.0%、28.6%、26.8%,显著高于对照组(10.8%、9.9%、9.4%,差异有统计学意义(P<0.01)。经生活指导后,对照组于空腹、餐后2小时和运动后的VLP阳性率分别下降至5.4%、4.0%、4.5%,差异有统计学意义(P<0.05);而观察组的VLP阳性率无明显变化(P>0.05)。结论餐后SMI患者的VLP阳性率显著高于非餐后SMI患者,推测其在SMI患者中发生心肌梗死或猝死的危险性最高,且一般生活指导并不能降低其危险性。     

Behavior of late ventricular potentials in acute experimental myocardial ischemia

Locally retarded depolarizations of the ischaemic myocardium are regarded as frequent trigger mechanisms of dangerous ventricular arrhythmias. Up to now, however, there are scarcely systematic investigations concerning their concrete developmental conditions in man, since late potentials can be made evident only by means of expensive invasive methods or signal mediation techniques. Therefore, an animal model should be built, which is suitable for the control of new therapy conceptions with antiarrhythmic drugs. The investigations were performed on 22 pigs in whom under insufflation anaesthesia altogether 10 pressure, flow and contractility parameters as well as 6 epicardial ECG signals were continuously recorded. The episodes of ischaemia were caused by LAD occlusions of different duration and intensity. Typical late potentials could be registered in 5 animals who all had survived complete interruptions of the coronary blood flow of longer than 10 min. The mean duration of the late potentials was 20 +/- 9.2 ms, their amplitudes reached from 150 to 600 microV. Also with regard to time and cycle constancy, the delay of the late Q-potential and the morphology they corresponded to the homogeneous phenomenon, known from man. They always could be derived only from electrodes outside the immediate zone of ischaemia. Neither partial occlusions nor complete interruption of the coronary blood flow in intervals shorter than 10 minutes led to the development of a late potential. The animal model used altogether appears very suitable to investigate the medicamentous influencibility of arrhythmogenic areas of the myocardium under direct control of the dynamic behaviour of ventricular late potentials.     

Occurrence of ventricular late potentials in patients with active acromegaly

OBJECTIVE: Patients with acromegaly have an increased risk of ventricular dysrhythmias and sudden death. Late potentials in a signal-averaged electrocardiogram (SAECG), a predictor of ventricular dysrhythmias, are frequently seen in patients after previous myocardial infarction, but little is known about the prevalence of late potentials in acromegaly. The aim of our study was to investigate the prevalence of late potentials in patients with acromegaly and their relation to the activity of the disease and to myocardial hypertrophy. PATIENTS: The study included 48 patients with acromegaly [27 males, 21 females, mean age 52.3 +/- 14.2 years, 16 active disease, 32 cured or 'well controlled', under treatment with sandostatin analogues (12/32)] and 38 healthy volunteers as a control group. RESULTS: Late potentials were detected in 9/16 (56%) patients with active acromegaly vs. 2/32 (6%) with cured/well controlled acromegaly (P = 0.001), defined as normal age-related IGF-1 levels and GH levels suppressible below 1 microg/l after an oral glucose load (75 g). Late potentials were not related to muscle mass index (127 +/- 35 active vs. 123 +/- 34 g/m2 cured/well controlled). The association of disease activity with the detection of late potentials was independent of age, gender, duration of the disease and body mass index. In comparison to the control group, the prevalence of late potentials was significantly higher in patients with acromegaly (23%) than in the control group (0%; P < 0.001). CONCLUSIONS: Late potentials in the SAECG are frequently seen in active acromegaly and may represent an early and sensitive parameter to detect myocardial injury in acromegaly.     

心肌再灌注对犬心室晚电位的影响

对犬进行冠状动脉二期结扎,建立心肌梗死模型,应用心表组合电极标测心室晚电位,观察再灌注对其影响。结果发现:心室晚电位阳性再灌犬,晚电位100％转阴。未灌犬无一例转阴。心室晚电位阳性再灌犬恶性心律失常发生率与晚电位阴性再灌犬相比,无显著差异。提示1.再灌注是使心室晚电位转阴的可靠方法;2.心室晚电位与再灌注心律失常无关;3.对急性心肌梗塞后心室晚电位阳性者,应积极进行心肌再灌注治疗。     

Significance of ventricular late potentials in non-ischaemic dilated cardiomyopathy.

To assess the incidence and clinical significance of ventricular late potentials in non-ischaemic dilated cardiomyopathy, 51 consecutive (44 male, seven female, mean age 53 +/- 11 years) patients with dilated cardiomyopathy were studied. Twenty-eight patients (55%) were in New York Heart Association functional class III or IV, 34 out of 51 (76%) had a left ventricular ejection fraction of less than 40%, 10 out of 51 (20%) had a history of sustained ventricular tachycardia (VT), 24 out of 37 (65%) had runs of non-sustained ventricular tachycardia during Holter monitoring and 15 out of 51 (29%) had a left bundle branch block. A signal-averaged electrocardiogram (gain 10(6) x, bipolar chest leads, filters 100-300 Hz) was performed in all the patients; late potentials were considered present if the total filtered QRS duration was longer than 118 ms and the interval between the end of QRS and the voltage 40 microV was more than 40 ms in the absence of left bundle branch block (total filtered QRS duration greater than 140 ms and interval between the end of QRS and the voltage 40 microV greater than 50 ms in the presence of left bundle branch block). Ventricular late potentials were detected in 22 out of 51 patients (43%). Late potentials were present in 80% (eight out of 10) of patients with sustained ventricular tachycardia but in only 34% (14 of 41) without sustained ventricular tachycardia (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)