冠心病患者运动试验引起QRS波增宽的临床意义

目的讨论冠心病患者在运动试验中引起的QRS波增宽及其增宽强度和冠心病缺血严重程度(病变涉及冠状动脉的支数)之间的关系.方法追踪心电图运动试验阳性且在半年内行冠状动脉造影检查的冠心病患者,重新测量和分析他们的心电图运动试验的记录资料,观察在运动试验内QRS波的增宽及其增宽程度,对比冠状动脉造影病变血管支数而发现相关性.结果冠状动脉患者在心电图运动试验中QRS波有不同程度的增宽.1支血管病变组平均增宽4.4 ms,2支病变组平均增宽7.9 ms,3支病变组平均增宽13.5 ms.结论冠心病患者在心电图运动试验当中QRS波有增宽,而且这种增宽的程度和冠状动脉受累的支数有密切关系.     

Artificial attenuation of ECG voltage produces shortening of the corresponding QRS duration: clinical implications for patients with edema

BACKGROUND: Prolonged QRS duration (QRSd) is a useful index for the management of patients with congestive heart failure (CHF). QRSd is affected by changes in the ECG voltage (ECGV) in the context of development and amelioration of peripheral edema (PERE), independent of underlying pathology. Nowadays, physicians accept QRSd measured by computer techniques. The latter offers the possibility of testing the hypothesis that artificial alteration of the ECGV, simulating effects of PERE, could lead to changes in the QRSd. METHODS: To this end, voltage was attenuated by 25%, 50%, and 75% in 100 digital ECGs recorded from normal subjects and in 20 patients with complete left bundle branch block (LBBB), by merely increasing the calibration strength by 4/3, 2, and 4, respectively, and by using the same data. RESULTS: All ECGs were analyzed by the same computer program and this led to a reduction of global QRSd by 2.3 +/- 2.9%, 5.7 +/- 4.0%, and 11.9 +/- 6.2%, respectively, in the normal subjects, and 1.6 +/- 1.4%, 3.4 +/- 1.7%, and 8.2 +/- 3.6%, respectively, in the patients with LBBB. Correlation of the percent change in the global QRSd and the percent change in ECGV was good with an r = 0.65, and P = 0.00005 in the normal subjects, and an r = 0.74 and P = 0.00005 in the patients with LBBB. CONCLUSIONS: Apparent shortening in QRSd as a function of ECGV attenuation due to PERE could have implications in the follow-up of patients with CHF, and their selection for implantable cardioverter/defibrillators, or cardiac resynchronization therapy.     

Method for mapping cardiac arrhythmia in real time using microprocessor-based systems

The paper deseribes a method for mapping cardiac arrhythmias in real time using an 8 bit microprocessor system, the aim being to produce a monitor display that is ergonomically an improvement on the raw ECG signal in that its interpretation by medical staff is less onerous. Two characteristics are extracted from each QRS complex, one representing rhythm and the other the morphology of the complex. Both are easily implemented on microprocessor-based systems and together they define a twodimensional display divided into four primary diagnostic regions. The performance of the proposed system has been compared with that of another two-dimensional algorithm commonly used in this field, the cross-correlation scatter diagram, by applying both to the same sample of complexes. The method proposed in the paper was found to be both faster and more discriminating.     

Generation of digital time database from paper ECG records and Fourier transform-based analysis for disease identification

ECG signals recorded on paper are transferred to the digital time database with the help of an automated data extraction system developed here. A flatbed scanner is used to form an image database of each 12-lead ECG signal. Those images are then fed into a Pentium PC having a system to extract pixel-to-pixel co-ordinate information to form a raw database with the help of some image processing techniques. These raw data are then ported to the regeneration domain of the system to check the captured pattern with the original wave shape. The sampling period of each ECG signal is computed after detection of QRS complex. Finally, discrete Fourier transform of the generated database is performed to observe the frequency response properties of every ECG signal. Some interesting amplitude properties of monopolar chest lead V4 and V6 are noticed which are stated.     

A new screening method to diagnose coronary artery disease using multichannel magnetocardiogram and simple exercise

Background: Magnetocardiography (MCG) is a non-contact mapping technique to record cardiac action currents. The Master's two-step electrocardiogram (ECG) test is a simple exercise method for screening coronary artery disease (CAD), but it is inadequate concerning the sensitivity. Our aim was to develop a new screening method using multichannel MCG instead of ECG. Methods: Thirty subjects (aged 54 ± 16 years, 27 males), 17 of whom had CAD confirmed by coronary angiography, underwent the Master's exercise ECG test. After the exercise, MCG signals were acquired every minute during recovery with a 64-channel MCG system (MC-6400, Hitachi Ltd). We integrated tangential components of the MCG signals within QRS (during 20, 40, 80, and 120 ms centering on R-wave peak) immediately after exercise (Iex) and 5 minutes after exercise (Irec). The exercise-induced change of currents [(Iex-Irec)/Irec] was determined and normalized for each channel, and the maximal change among 64 channels, maximal QRS integral change, was used as a diagnostic index for myocardial ischemia. Results: The maximal QRS integral change during 40 ms was significantly higher in the CAD group than in the control group (0.81 ± 0.51 vs. 0.36 ± 0.19, p < 0.01). A sensitivity and specificity for predicting CAD by the change > 0.44 were 82 % and 85 %, respectively, yielding a diagnostic accuracy of 83 %. The conventional Master's ECG test identified the CAD patients with a diagnostic accuracy of 63 % (sensitivity 47 %, specificity 85 %). Conclusion: The Master's two-step exercise test with a 64-channel MCG system showed the high diagnostic accuracy, despite of non-contact recording and simple exercise. The magnetic field in the depolarization process has the potential to detect the subtle myocardial ischemia induced by exercise. Received: 20 June 2002, Returned for 1. revision: 11 July 2002, 1. Revision received: 3 September 2002, Returned for 2. revision: 25 September 2002, 2. Revision received: 10 October 2002, Accepted: 14 October 2002 Correspondence to: S. Nakatani, MD, PhD     

Cardiac vulnerability assessment from electrical microvariability of high-resolution electrocardiogram

Patients susceptible to malignant arrhythmias often have an increased beat-to-beat variation of the T-wave of the electrocardiogram. Variability analysis of the T-wave is increasingly used for non-invasive risk assessment. The aim of this study is to evaluate intra-QRS beat-to-beat signal variation and to compare it to ST-T variation. The beat-to-beat, microvolt variation of the QRS and the ST-T segment from 44 patients with coronary heart disease at high risk of suffering from malignant arrhythmias and from 51 healthy volunteers are compared. Variation analysis is carried out on 250 consecutive sinus beats from high-resolution electrocardiograms. The individual beats are filtered using a waveform-independent, cubic spline-filter. A variability index of the QRS and ST-T segments is calculated as the integrated standard deviation of corresponding samples inside the area of interest. Patients at risk of suffering from malignant arrhythmias have a significantly higher variability index of both the QRS (median 44.5 ms against 34.7 ms, p<0.001) and the ST-T segment (median 20.5 ms against 9.8 ms, p<0.001) compared to the group of healthy subjects. The discriminative ability of the odds variability indices of the QRS and ST-T segments are not statistically different, the ratios being 7.8 (QRS) and 12.6 (ST-T). We conclude that patients at high risk of suffering from malignant arrhythmias are characterised by an increased beat-to-beat microvolt variation of both the QRS and the ST-T segment. Further studies are necessary to evaluate the prognostic potential of depolarisation variability.     

Noninvasive visualization of multiple simultaneously activated regions on torso magnetocardiographic maps during ventricular depolarization

The time course and instantaneous distribution of the electrophysiologic processes of the human heart were analyzed by using a multichannel superconducting quantum interference device (SQUID) system, enabling the tangential components of the cardiac magnetic fields to be measured. By visualizing the changing magnetic field pattern in a two-dimensional presentation of the anterior and posterior torso during depolarization, the existence of more than one simultaneously activated region and the effective intracardiac current distribution were estimated without using a mathematical algorithm. The mid-to-late QRS complex when the myocardium has widespread depolarizing regions was analyzed using this technique. Even in an early stage of the QRS, two discrete active regions were observed in the magnetic field maps, in all nine subjects (adults with normal hearts). Furthermore, differences in the current distribution between the front and back active region were observed.     

冠心病病人运动试验时QRS间期延长与冠脉狭窄关系探讨

目的 探讨冠心病病人心肌缺血时ＱＲＳ间期的变化及其与冠脉狭窄的关系，并结合现有资料探讨其可能机制。方法 １２０名患分别于１月内予心导管检查及蹬车心电图试验试验。结果 ３０名患冠脉造影正常，９０我有冠脉狭窄病变。正常运动时ＱＲＳ间期缩短（－２．９ｍｓ，可信区间－６．０至０．２），而冠脉狭窄运动时ＱＲＳ间期延长。运动诱发ＱＲＳ间期延长与冠脉狭窄支数相关，（４．５ｍｓ／１支，７．９ｍｇ／２支，１     

Taquicardia mediada por via Mahaim

We present the case of a previously healthy 42‐year‐old man who attended the emergency department due to a sudden onset of rapid and regular palpitations. The ECG showed 190 bpm, wide QRS with left bundle branch block tachycardia. He was started on amiodarone with progression to 230 bpm, wide QRS tachycardia with multiple morphologies, followed by spontaneous conversion to sinus rhythm, normal PR interval and rS pattern in LIII. The echocardiogram was negative for structural heart disease. The electrophysiological study demonstrated the presence of an accessory pathway with anterograde decremental conduction and no retrograde conduction. Both episodes of clinical tachycardia were induced. A diagnosis of Mahaim fiber‐mediated antidromic atrioventricular reentrant tachycardia and pre‐excited atrial fibrillation was made. Mapping was performed with detection of an M potential (His‐like) at the lateral region of the tricuspid ring followed by radiofrequency ablation with immediate success criteria. Post‐ablation there was a change to a qR pattern in LIII. At 12‐months follow‐up there was no recurrence of the tachycardia.     

A low-cost general-purpose analogue QRS wave detector

An analogue circuit for QRS detection using four low-cost operational amplifiers is described. The circuit was compared with several other types of preprocessors from commercially available arrhythmia monitors by means of arrhythmia test tapes. In a file of 946 various QRS complexes it detected 98% correctly, which is comparable with the performance of the other preprocessor circuits, at, however, a significantly lower component cost. Several advantages of the circuit are stressed, and possible applications for particular purposes are suggested.