Tp—e时间及离散度对Brugada综合征患者预后的分析

目的探讨T波峰-末时间（Tp—e时间）及离散度与Brugada综合征患者预后的关系。方法采用动态心电图分析仪测量31例Brugada综合征患者的Tp—e时间及离散度。随访2～6年，每年2次，心脏事件为猝死幸存和（或）发生室性心动过速／心室颤动。结果无症状者发生心脏事件的Tp—e时间及离散度分别为（116．00±8．94）ms、（3300±1150）ms；未发生心脏事件者分别为（8666±1000）ms、（22．00±6．30）ms，差异有显著统计学意义（均P〈0．01）。有症状者再发生心脏事件的Tp—e时间及离散度分别为（108．50±10．69）ms、（3420±1060）ms；未发生心脏事件者分别为（85．45±9．34）ms、（18．10±12．60）ms，差异有显著统计学意义（均P〈0．01）。Tp—e时间及其离散度预测心脏事件发生的ROC曲线下面积分别为0947、0703。结论Tp—e时间及离散度可作为一种无创手段用于预测Brugada综合征患者发生心脏事件。     

氯丙嗪对精神分裂症患者心电图的影响

目的探讨口服盐酸氯丙嗪片对精神分裂症患者心电图的影响，为临床合理用药提供参考。方法选择笔者所往医院2009年2月～2011年1月收治的120例精神分裂症患者，给予盐酸氯丙嗪片单一用药治疗，分别t开始治疗1、3、6个月后检查患者心电图，比较3次检查结果心电图异常发生率的变化。结果治疗6个月的患者心电图异常率明显高于治疗3个月后的，差异有统计学意义（P〈0．05）。治疗后3个月患者心电图异常率明显高于治疗后1个月，差异有统计学意义（P〈0．05）。结论长期使用氯丙嗪可造成精神分裂症患者心电图异常，用药时间越长，其对心脏功能的影响程度越大，在今后的临床用药过程中应注意保护心脏功能。     

The application of subspace preconditioned LSQR algorithm for solving the electrocardiography inverse problem

Regularization is an effective method for the solution of ill-posed ECG inverse problems, such as computing epicardial potentials from body surface potentials. The aim of this work was to explore more robust regularization-based solutions through the application of subspace preconditioned LSQR (SP-LSQR) to the study of model-based ECG inverse problems. Here, we presented three different subspace splitting methods, i.e., SVD, wavelet transform and cosine transform schemes, to the design of the preconditioners for ill-posed problems, and to evaluate the performance of algorithms using a realistic heart-torso model simulation protocol. The results demonstrated that when compared with the LSQR, LSQR-Tik and Tik-LSQR method, the SP-LSQR produced higher efficiency and reconstructed more accurate epcicardial potential distributions. Amongst the three applied subspace splitting schemes, the SVD-based preconditioner yielded the best convergence rate and outperformed the other two in seeking the inverse solutions. Moreover, when optimized by the genetic algorithms (GA), the performances of SP-LSQR method were enhanced. The results from this investigation suggested that the SP-LSQR was a useful regularization technique for cardiac inverse problems.     

Wavelet analysis of high-resolution signal-averaged ECGs in postinfarction patients

The authors present an original method for the discrimination of patients prone to ventricular tachycardia. The wavelet transform, which is a new time-scale technique suitable for transient signal detection, was applied to bipolar unfiltered X, Y, Z signal-averaged electrocardiograms in 20 postinfarction patients with sustained ventricular tachycardia, in 20 myocardial infarction patients without ventricular tachycardia, and in 10 healthy subjects. An improved automated algorithm for the detection and localization of sharp variations of the signal, based on coherent detection of the local maxima of the wavelet transform, was developed. A risk stratification method, based on the detection of at least one singularity at or after a point defined with reference to the QRS onset, was assessed. The optimum cutoff point, found 98 ms after the onset of QRS, provides a specificity of 90% and a sensitivity of 85%. The authors conclude that wavelet analysis makes it possible, in this group of patients, to discriminate those with ventricular tachycardia. It yields better results than those obtained from the conventional time-domain approach.     

Spectral Analysis of the High Resolution QRS Complex During Exercise-Induced Ischemia

Background: The effect of acute myocardial infarction and regional ischemia on the frequency content of the ECG signal has been described by several investigators. In the present study, the feasibility of assessing changes in the QRS spectrum during exercise testing, and whether these changes are related to the occurrence of ischemia were examined. Methods: Spectral analysis of the high resolution ECGs from leads V₃, V₄, V₅, and V₆ were performed in two groups of male subjects before, during, and following treadmill exercise testing. Group A included 32 coronary artery disease (CAD) patients, with arteriographically proven >75% obstruction of at least two main coronary arteries, and group B included 30 healthy subjects, without history or symptoms of CAD. Signal averaging and filtering techniques were used in order to enhance the signal-to-noise ratio of the recorded ECGs. The power spectrum of the averaged QRS waveform for the different stages of the exercise testing was computed using a Fast Fourier Transform, and the slope of the linear regression line was found in the frequency range 7.81–249.92 Hz on the plot of log((amplitude)²) versus log(frequency). Results: Regression line slopes immediately after peak exercise were significantly lower for the CAD group than for the healthy subjects in 3 of the 4 examined leads. No significant changes in slopes were found between the two groups at rest or during late recovery. Comparing the differences between slopes at different stages of the test revealed that the difference between postexercise slope and rest slope has lower mean values for the CAD group in all four leads, with a significant difference in lead V6, and for the difference between postexercise slope and recovery slope, lower mean values were found for the CAD group in all four leads, with a significant difference in V5 and V6. Conclusions: These findings indicate that ischemic changes affect the power spectrum of the QRS complex, and result in a steeper regression line on a log-log scale.     

Asymptomatic hyperglycaemia is associated with increased intimal plus medial thickness of the carotid artery

Summary Atherosclerotic changes have not been demonstrated directly in asymptomatic hyperglycaemic non-diabetic subjects, although high mortality due to coronary heart disease has been reported. We measured arterial wall thickness non-invasively, in order to directly demonstrate atherosclerosis of the carotid arteries of hyperglycaemic non-diabetic subjects and to evaluate its risk factors.The thicknesses of the intimal plus medial complex (IMT) of the carotid arteries of 112 asymptomatic hyperglycaemic non-diabetic subjects (aged 22–81, 95 males and 17 females) were compared with those of 55 healthy male subjects and 211 non-insulin-dependent NIDDM male diabetic patients. The subjects were subgrouped into impaired glucose-tolerant (IGT) subjects who had a 2-h glycaemic level of more than 7.8 mmol/l, and non-IGT subjects whose 2-h glycaemic levels were within 6.7–7.7 mmol/l.Non-IGT and IGT subjects showed significantly greater IMTs than age-matched healthy males and showed no significant differences compared to age-matched NIDDM patients. Multivariate analysis demonstrated that the risk factors for IMT of non-IGT and IGT subjects were age and systolic blood pressure. According to data on the accumulation of atherogenic risks (hypertension, dyslipidaemia, and smoking), IMT increased linearly in non-IGT and IGT subjects. However, non-IGT and IGT subjects without hyperlipidaemia, hypertension, or smoking risk still had significantly greater IMT than age-matched normal males (1.019±0.063 vs 0.770±0.111 mm, p<0.05). Prevalence of ECG-indicated coronary heart disease was significantly higher in hyperglycaemic non-diabetic subjects and NIDDM with increased carotid arterial wall thickness (IMT 1.1 mm) than in those without increased thickness (IMT<1.1 mm). Asymptomatic hyperglycaemic non-diabetic subjects have increased thickness of their carotid arteries compared to age-matched male NIDDM patients. As one of several independent risk factors, mild hyperglycaemia advances atherosclerosis, which leads to coronary heart disease.Abbreviations IMT Intimal plus medial complex - NIDDM non-insulin-dependent diabetes mellitus - IGT impaired glucose tolerance - CHD coronary heart disease - T-Chol serum total cholesterol - HDL-C high-density lipoprotein cholesterol - TG serum triglycerides     

Relation between ventricular fibrillation voltage and probability of defibrillation shocks: Analysis using Hilbert transforms

We used Hilbert transforms to re-evaluate the previously reported correlation between defibrillation shock outcome and absolute ventricular fibrillation voltage (AVFV). Previously in the literature, single values of AVFV acquired just prior to shock delivery were used to show a correlation between AVFV and shock outcome. In subsequent studies, a modified analysis procedure was used to show a correlation between shock outcome and moving average of AVFV. The use of single values of AVFV makes the AVFV sensitive to the local phase of the electrocardiographic (ECG) waveform, whereas moving averages are weighted by previous values of the ECG. The envelope is independent of the phase of the ECG and is not weighted by previous values of ECG as is the moving average. We explored, therefore, whether the AVFV computed from the envelopes of the ECG showed a stronger correlation with shock outcome than single values and moving averages of the AVFV. We estimated envelopes using the Hilbert transform. Orthogonal ECGs (sagittal, X; transverse, Y; and longitudinal, Z) were recorded from 11 dogs during 10 seconds of electrically induced ventricular fibrillation followed by a defibrillation shock with 50% probability of success. We used transvenous (right ventricular apex to subcutaneous patch) leads to deliver defibrillation shocks. Results from 236 successful and 249 unsuccessful trials showed, in contrast with the previously reported correlation, that moving average of AVFV was not higher for successful trials. In the Z direction, unsuccessful trials had higher voltage than successful trials (P < .05). Comparison of envelope voltages between successful and unsuccessful trials did not show any consistent and statistically significant differences. Although there were some methodological differences between ours and the previously reported studies, they are unlikely to have caused the discrepant observations. Our results suggest, therefore, that the absolute voltage of ECG during ventricular fibrillation is not robustly correlated with shock outcome.     

ST-recovery loop of exercise-induced ST deviation in the identification of coronary artery disease: which parameters should we measure?

This study aimed to characterize the ST-recovery loop and assess which range of heart rates (HRs) best discriminates between patients with and without significant coronary artery stenosis. Bicycle exercise tests were undertaken in 44 men and 18 women with coronary artery disease (CAD) and in 59 controls (26 men, 33 women) in the same age range with no signs of CAD. The ST level and the ST-segment slope were continuously monitored, and changes from rest to peak exercise and to 4 min after exercise, respectively, were calculated. Plotting the ST level against HR gives the STHR loop, characterized by the normalized area (NA(alpha)) circumscribed by the ST level during and after exercise from alpha% to 100% of the HR range. Eight values of alpha between 20% and 90% were investigated, and chest and extremity leads were investigated separately. Optimal alpha was found to be < or =70% in men and < or =30% in women. Change in ST-segment slope was the only parameter that gave significant additional discriminating power in both men and women once the area had been taken into account. We conclude that NA(alpha) for extremity and chest leads have similar weights, and that a substantial part of the STHR loop should be taken into consideration, especially in women. NA(30) was superior to end-exercise ST-depression and STHR loop orientation (as defined by the sign of NA(90)) in both men and women, and to ST/HR index in men, in identifying CAD.     

Late QRS Activity in Signal‐Averaged Magnetocardiography,Body Surface Potential Mapping,and Orthogonal ECG in Postinfarction Ventricular Tachycardia Patients

Background: Delayed electrical activity necessary for re‐entrant ventricular tachycardia (VT) is detectable noninvasively with high resolution techniques. We compared high resolution signalaveraged analysis of magnetocardiography (MCG), body surface potential mapping (BSPM), and orthogonal three‐lead ECG (SA‐ECG) in the identification of patients prone to VT after myocardial infarction (Ml). Methods: Patients with remote myocardial infarction and cardiac dysfunction were studied, 22 with (VT group) and 22 without VT (control group). MCG with seven channels and BSPM with 63 and SA‐ECG with three orthogonal leads were registered. After signal‐averaging and highpass filtering, three time domain analysis (TDA) parameters describing late electrical activity were computed: QRS duration (QRSd), root mean square amplitude (RMS) of the last 40 ms of QRS, and the duration of the low‐amplitude QRS end (LAS). Results: All parameters by each method were significantly different between the patients’groups. For example, LAS parameter in MCG was 59 (SD 22) ms in the VT group vs. 37 (SD 13) ms in controls (P < 0.001), 77 (SD 22) ms vs. 56 (SD 19) ms in BSPM (P = 0.002), and 60 (SD 24) ms vs. 39 (SD 22) ms in SA‐ECG (P = 0.005). The combination of LAS parameter in MCG and SA‐ECG resulted in improved performance in comparison to any single parameter with 95% sensitivity and 68% specificity. Conclusions: All three high resolution methods identified VT propensity among post‐Mi patients with cardiac dysfunction and between‐method differences were small. Information in MCG and SA‐ECG may be complementary and their combination could be of value in postinfarction arrhythmia risk assessment. A.N.E. 2002;7(4):389–398     

Computer‐Based Analysis of Dynamic QT Changes: Toward High Precision and Individual Rate Correction

Background: New strategies are needed to improve the results of automatic measurement of the various parts of the ECG signal and their dynamic changes. Methods: The EClysis software processes digitally‐recorded ECGs from up to 12 leads at 500 Hz, using strictly defined algorithms to detect the PQRSTU points and to measure ECG intervals and amplitudes. Calculations are made on the averaged curve of each sampling period (beat group) or as means ± SD for beat groups, after being analyzed at the individual beat level in each lead. Resulting data sets can be exported for further statistical analyses. Using QT and R‐R measured on beat level, an individual correction for the R‐R dependence can be performed. Results: EClysis assigns PQRSTU points and intervals in a sensitive and highly reproducible manner, with coefficients of variation in ECG intervals corresponding to ca. 2 ms in the simulated ECG. In the normal ECG, the CVs are 2% for QRS, 0.8% for QT, and almost 6% for PQ intervals. EClysis highlights the increase in QT intervals and the decrease of T‐wave amplitudes during almokalant infusion versus placebo. Using the observed linear or exponential relationships to adjust QT for R‐R dependence in healthy subjects, one can eliminate this dependence almost completely by individualized correction. Conclusions: The EClysis system provides a precise and reproducible method to analyze ECGs. A.N.E. 2002;7(4):289–301