Global electrical heterogeneity as a predictor of cardiovascular mortality in men and women.

Aims: The aim of this study was to investigate the contribution of depolarization and repolarization abnormalities, specially abnormalities in global electrical heterogeneity of heart in cardiovascular disease (CVD) and all-cause mortality. Methods and results: Eight hundred and forty men and 911 women, average age of 63 years participated in this study with average follow-up was 14 years. Six electrocardiogram/vector electrocardiogram (ECG/VECG) markers QRS-duration, QTc-interval, QRST-angle, sum of absolute QRST integral (SAI QRST), T-wave roundness, and TV1-amplitude were estimated from VECG measurements. Hazard ratios (HRs) for CVD events (164 deaths) and all-cause mortality (383 deaths) for ECG parameters were calculated. Electrocardiogram or vector electrocardiogram parameter models adjusted for risk clinical factors showed that strongest predictors for CVD mortality were QRST-angle (HR 3.44, 95% confidence interval 2.12-5.36), QTc-interval (2.72, 1.73-4.29), and T-wave roundness (2.09, 1.26-3.46) among men. The strongest ECG/VECG parameters for CVD death were QRST-angle (2.47, 1.37-4.45), SAI QRST (2.37, 1.23-4.6), and QTc-interval (2.15, 1.16-4.01) among female participants. Multivariable adjusted models revealed that strongest independent ECG predictors for CVD death were QRST-angle, QTc-interval, resting heart rate, and T-roundness for men, QRST-angle and SAI QRST for women. QRST-angle, QTc-interval, resting heart rate, and T-roundness were associated with all-cause mortality in male population, although none of the ECG/VECG parameters predicted all-cause mortality among women. Conclusion: Characteristics of global electrical heterogeneity QRST-angle and QTc-interval in men and QRST-angle and SAI QRST among females were strong and independent risk markers for cardiovascular mortality. These parameters provide new additional ECG tools for cardiovascular risk stratification.

ECG-derived spatial QRS-T angle is strongly associated with hypertrophic cardiomyopathy.

INTRODUCTION: ECG-derived vectorcardiography (VCG) has diagnostic and prognostic value in various diseases. Hypertrophic cardiomyopathy (HCM), a genetic disease with unexplained left ventricular hypertrophy, is one of the most common causes of sudden cardiac death (SCD) in young persons. Genotype positive status is associated with increased risk of systolic dysfunction, heart failure, and (SCD). Herein, we aimed to determine the diagnostic utility of derived VCG parameters in a large cohort of genotyped HCM patients. METHODS: Between 1997 and 2007, genetic testing was performed on 1053 unrelated patients with HCM. Of these, 967 had 12-lead ECGs suitable for computerized derivation of VCG parameters, including the spatial mean and peaks QRS-T angles, spatial ventricular gradient (SVG), spatial QRS, QT, and Tpeak-Tend (TpTe) intervals. ECGs were also evaluated using Seattle ECG criteria. Differences between HCM patients and healthy controls as well as between genotype positive versus genotype negative HCM patients were assessed. RESULTS: Spatial peaks (129.3±26.4 vs.30.5±24.2 degrees) and spatial mean QRS-T angles (121.8±38.6 vs. 47.3±27.6 degrees) were significantly higher in patients with HCM than in controls (P<0.001). The spatial peaks and mean QRS-T angles identified 94% and 84% of HCM patients, respectively, while Seattle criteria identified 70.7% of patients (P<0.001). Genotype positive patients had higher spatial mean QRS-T angles, spatial TpTe (P<0.001 respectively), spatial peaks QRS-T angles (P=0.017) and lower SVG (P<0.001) than genotype negative patients. CONCLUSIONS: ECG-derived spatial QRS-T angles can differentiate patients with HCM from controls and could provide a better tool than traditional Seattle criteria. Clinical usefulness of VCG to differentiate genotype-negative from genotype-positive patients has yet to be established.

Transformation of the Mason-Likar 12-lead electrocardiogram to the Frank vectorcardiogram.

Vectorcardiograpic (VCG) parameters can supplement the diagnostic information of the 12-lead electrocardiogram (ECG). Nevertheless, the VCG is seldom recorded in modern-day practice. A common approach today is to derive the Frank VCG from the standard 12-lead ECG (distal limb electrode positions). There is, to date no direct method that allows for a transformation from 12-lead ECGs with proximal limb electrode positions (Mason-Likar (ML) 12-lead ECG), to Frank VCGs. In this research, we develop such a transformation (ML2VCG) by means of multivariate linear regression on a training data set of 545 ML 12-lead ECGs and corresponding Frank VCGs that were both extracted surface potential maps (BSPMs). We compare the performance of the ML2VCG method against an alternative approach (2step method) that utilizes two existing transformations that are applied consecutively (ML 12-lead ECG to standard 12-lead ECG and subsequently to Frank VCG). We quantify the performance of ML2VCG and 2step on an unseen test dataset (181 ML 12-lead ECGs and corresponding Frank VCGs again extracted from BSPMs) through root mean squared error (RMSE) values, calculated over the QRST, between actual and transformed Frank leads. The ML2VCG transformation achieved a reduction of the median RMSE values for leads X (13.9µV; p<.001), Y (15.1µV; p<.001) and Z (2.6µV; p=.001) when compared to the 2step transformation. Our results show that the 2step method may not be optimal when transforming ML 12-lead ECGs to Frank VCGs. The utilization of the herein developed ML2VCG transformation should thus be considered when transforming ML 12-lead ECGs to Frank VCGs.

Prediction of cardiovascular death and myocardial infarction by the QRS-T angle and T vector loop morphology after angioplasty in stable angina pectoris: an 8-year follow-up.

Reliable cardiovascular (CV) risk assessment by a noninvasive tool would be of great value for CV event prevention. The present study consists of 187 coronary artery disease patients with 8 years of follow-up. Eight vectorcardiographic parameters characterizing different aspects of ventricular repolarization were analyzed at baseline: (1) the ST-segment (ST-VM), (2) the T vector angles (QRS-T angle, Televation, and Tazimuth), (3) the T vector loop morphology (Tavplan and Teigenvalue), and (4) Tarea and Tpeak-end. Cardiovascular death, myocardial infarction (MI), and repeated revascularization were traced via national registries. There were 16 CV deaths and 19 MIs; 89 patients remained free from CV events and revascularization. Ventricular repolarization parameters independently predicted CV death (widened QRS-T angle) and new MI (increased Tavplan) during follow-up. CV mortality was associated with increased divergence between depolarization and repolarization waves (widened QRS-T angle). Increased Tavplan, presumably reflecting heterogeneous repolarization, predicted future MI, which is a novel finding.

Prevalence of interatrial block in healthy school-aged children: definition by P-wave duration or morphological analysis.

BACKGROUND: P waves > or = 110 ms in adults and > or = 90 ms in children are considered abnormal, signifying interatrial block, particularly in the first case. METHODS: To evaluate the prevalence of interatrial block in healthy school-aged children, we obtained 12-lead digital ECGs (Cardioperfect 1.1, CardioControl NV, Delft, The Netherlands) of 664 healthy children (349 males/315 females, age range 6-14 years old). P-wave analysis indices [mean, maximum and minimum (in the 12 leads) P-wave duration, P-wave dispersion, P-wave morphology in the derived orthogonal (X, Y, Z) leads, as well the amplitude of the maximum spatial P-wave vector] were calculated in all study participants. RESULTS: P-wave descriptor values were: mean P-wave duration 84.9 + or - 9.5 ms, maximum P-wave duration 99.0 + or - 9.8 ms, P dispersion 32.2 + or - 12.5 ms, spatial P amplitude 182.7 + or - 69.0 microV. P-wave morphology distribution in the orthogonal leads were: Type I 478 (72.0%), Type II 178 (26.8%), Type III 1 (0.2%), indeterminate 7 (1%). Maximum P-wave duration was positively correlated to age (P < 0.001) and did not differ between sexes (P = 0.339). Using the 90-ms value as cutoff for P-wave duration, 502 (75.6%) children would be classified as having maximum P-wave duration above reference range. The 95th and the 99th percentiles were in the overall population 117 ms and 125 ms, respectively. P-wave morphology type was not in any way correlated to P-wave duration (P = 0.715). CONCLUSIONS: Abnormal P-wave morphology signifying the presence of interatrial block is very rare in a healthy pediatric population, while widened P waves are quite common, although currently classified as abnormal.

The time course of new T-wave ECG descriptors following single- and double-dose administration of sotalol in healthy subjects.

INTRODUCTION: The aim of the study was to assess the time course effect of IKr blockade on ECG biomarkers of ventricular repolarization and to evaluate the accuracy of a fully automatic approach for QT duration evaluation. METHODS: Twelve-lead digital ECG Holter was recorded in 38 healthy subjects (27 males, mean age = 27.4 + or - 8.0 years) on baseline conditions (day 0) and after administration of 160 mg (day 1) and 320 mg (day 2) of d-l sotalol. For each 24-hour period and each subject, ECGs were extracted every 10 minutes during the 4-hour period following drug dosage. Ventricular repolarization was characterized using three biomarker categories: conventional ECG time intervals, principal component analysis (PCA) analysis on the T wave, and fully automatic biomarkers computed from a mathematical model of the T wave. RESULTS: QT interval was significantly prolonged starting 1 hour 20 minutes after drug dosing with 160 mg and 1 hour 10 minutes after drug dosing with 320 mg. PCA ventricular repolarization parameters sotalol-induced changes were delayed (>3 hours). After sotalol dosing, the early phase of the T wave changed earlier than the late phase prolongation. Globally, the modeled surrogate QT paralleled manual QT changes. The duration of manual QT and automatic surrogate QT were strongly correlated (R(2) = 0.92, P < 0.001). The Bland and Altman plot revealed a nonstationary systematic bias (bias = 26.5 ms + or - 1.96*SD = 16 ms). CONCLUSIONS: Changes in different ECG biomarkers of ventricular repolarization display different kinetics after administration of a potent potassium channel blocker. These differences need to be taken into account when designing ventricular repolarization ECG studies.

Measures of agreement for vectorcardiography data.

In this paper, nonparametric methods are proposed for quantifying agreement and disagreement between different measurement methods when the results of the measurements are rotation matrices. First, the expected squared distance between two matrices is used to quantify the measurement agreement. Two choices of such distance are considered-the Frobenius distance and geodesic distance. Second, the notion of 'concordance correlation coefficient', a commonly used measure of agreement, is extended to the space of rotation matrices. Such generalized concordance coefficient can be treated as a normalized expected squared distance. Since no two measurement systems can be expected to be in perfect agreement, it becomes necessary to define a notion of practical agreement. We define such a notion. Moreover, for both proposed methods, the percentile bootstrap procedure is implemented to provide a confidence interval to help make a decision concerning practical agreement/disagreement in real-life applications. The methodology is illustrated using two data sets, one based on an application involving vectorcardiography data (Biometrika 1972; 59:665-676) and the other based on a synthetic data set.

Contributions of myocardial ischemia and heart rate to ST segment changes in patients with or without coronary artery disease.

BACKGROUND: ST changes related to ischemia at different heart rates (HRs) have not been well described. We aimed to analyze ST dynamic changes by vectorcardiography (VCG) during pacing-induced HR changes for subjects with proven coronary artery disease (CAD) and without (non-CAD). METHODS: Symptomatic CAD patients scheduled for elective surgery were enrolled along with a non-CAD group. During anesthesia, both groups were placed at multiple ascending levels. VCG ST data, and in particular in ST change vector magnitude (STC-VM) from baseline, along with arterial and great coronary artery vein (GCV) blood samples were collected to determine regional myocardial lactate production. RESULTS: A total of 35 CAD and 10 non-CAD patients were studied over six incremental 10 beat/min HR increases. STC-VM mean levels increased in the CAD group from 9+/-5 to 131+/-37 microV (standard deviation) compared with non-CAD subjects with 8+/-3-76+/-34 microV. Myocardial ischemia (lactate production) was noted at higher HRs and the positive predictive value for STC-VM to detect ischemia was 58% with the negative predictive value being 88%. STC-VM at 54 microV showed a sensitivity of 88% and a specificity of 75% for identification of ischemia. CONCLUSIONS: Both HR and ischemia at higher HRs contribute to VCG ST elevation. Established ST ischemia detection concerning HR levels is suboptimal, and further attention to the effects of HR on ST segments is needed to improve electrocardiographic ischemia criteria.

Limited prognostic value of noninvasive assessment of reperfusion by continuous vectorcardiography in an unselected cohort of patients with acute ST-elevation myocardial infarction treated with thrombolysis.

AIMS: We studied the prognostic value of different reperfusion criteria of short-term continuous vectorcardiography (VCG) in an unselected cohort of 400 patients with ST-elevation myocardial infarction, treated at 4 coronary care units in Stockholm, Sweden, between 1999 and 2002. The main outcome measure was 1-year mortality. RESULTS: Of 400 study patients, 41 (10.2%) died within 1 year. One-year mortality in patients without reperfusion at 90 minutes, defined as ST resolution below 50% on VCG, was 11.6% compared with 9.0% in patients with reperfusion, (P = 0.4). Ninety-eight (24.5%) patients underwent intervention before discharge and percutaneous coronary intervention or coronary artery bypass grafting or both during the index admission. Percutaneous coronary intervention or coronary artery bypass grafting was related to improved 1-year survival (97 +/- 2% vs 87 +/- 2%, P = .0076). ST-vector magnitude resolution at 90 minutes was lower in patients who underwent intervention (P = .045). None of the reperfusion criteria of VCG was significantly associated with 1-year mortality. CONCLUSION: Our results show that noninvasive assessment of reperfusion by continuous VCG has limited prognostic value in unselected patients treated with thrombolysis because of ST-elevation myocardial infarction when subsequent revascularizations are performed. However, VCG might be useful in selecting patients for coronary angiography with subsequent revascularization.

Effects of thrombolysis on vectorcardiographic indices of ventricular repolarization: correlation with ST-segment resolution.

To investigate the effects of thrombolysis on vectorcardiographic (VCG) descriptors of ventricular repolarization in association with ST-segment resolution, 70 consecutively recruited patients with acute myocardial infarction underwent digital 12-lead electrocardiograms (ECGs) before and at 3 hours after thrombolysis. The alterations in the VCG descriptors spatial T amplitude and spatial QRS-T angle from the pre- to the post-thrombolysis ECG, as well as the ST-segment resolution, were calculated. Angiography revealed patency of the infarct-related coronary artery after thrombolysis in 52 (74%) patients (group A) and occlusion in 18 (26%) (group B). The spatial T amplitude was highly significantly reduced after thrombolysis in group A (P<.0001), but only marginally reduced in group B (P=.016). The spatial QRS-T angle was also significantly, although only marginally, reduced after thrombolysis in group A (P=.019), whereas it was not changed after thrombolysis in group B (P=.868). An ST-segment resolution of 60% and a 25% reduction in the spatial T amplitude after thrombolysis were able to identify patency of the infarct-related coronary artery with sensitivities of 90% and 77% and specificities of 94% and 74%, respectively. Both VCG descriptors were significantly affected by thrombolysis in patients with acute myocardial infarction, but constituted only moderate markers of thrombolysis efficacy, as evidenced by the presence of patency in the infarct-related coronary artery, compared with the ST-segment resolution.

Simplified [correction of Simlified] calculation of mean QRS vector (mean electrical axis of heart) of electrocardiogram.

In clinical practice assessment of the mean QRS axis (MQRSA) provides information related either with hypertrophy of the ventricles or conduction blocks. The method adopted by clinicians i.e. the inspection of the QRS voltage in six of the limb leads has inherent element of subjectivity of approximately 10degrees. Moreover, in certain condition, when there is ambiguity about differentiation of left axis deviation assessed by inspection method in to either hypertrophy of left ventricles or complete/hemi block of the left bundle branches, accurate measurement of the axis becomes necessary to arrive at the correct diagnosis. Though a formula based on area under R wave and S-wave of the same QRS complex has been derived for accurate measurement of axis, considering its use in the computer software, working with ordinary electrocardiograph the only method for accurate measurement of the QRS axis is plotting method i. e. the net voltages in Lead-I, and III on their respective axes which is not practicable in clinical settings. Although, calculation of MQRSA by area method gives an accurate assessment of MQRSA, some authors prefer measurement of axis by voltage method, as in cases of the right ventricular hypertrophy with a broad S-wave calculation of axis by area method may give erroneous results. Hence, to obtain correct measurement of MQRSA, we have derived a simplified formula based on the net voltage of QRS complexes in Lead-I and Lead-III. The formula derived is as follows, Tan(theta) =(I + 2III) divided by sqrt [3I], where I and III represent net voltage in Lead-I and III, theta = angle subtended with the axis Lead-I. The value of theta can be found by using scientific calculator or the table. In case net voltage of QRS complex in Lead-I being negative, the value of the theta should be subtracted from 180degrees to find the angle of mean QRS vector.

The effects of cigarette smoking on the heterogeneity of ventricular repolarization.

BACKGROUND: Although the circulatory effects of cigarette smoking have been studied extensively, its impact on ventricular repolarization has not been adequately evaluated. METHODS: The goal of our study was to determine whether cigarette smoking influences the spatial and temporal heterogeneity of ventricular repolarization in a population of young, healthy, male subjects. A digital 12-lead surface electrocardiogram was obtained from 1394 men recruited from the Hellenic Air Force and classified as smokers and nonsmokers. The maximum, minimum, and median QT intervals, QT dispersion (QT maximum - QT minimum), the rate-corrected maximum and median QT intervals, the slopes of the QT maximum/RR and QT median/RR regression equations, and the vectorcardiographic markers spatial T amplitude and spatial QRS-T angle were evaluated in the 2 groups. RESULTS: Heart rate was significantly higher (P <.001) in smokers (n =691) compared with nonsmokers (n = 703). QT maximum, QT minimum, and QT median were significantly lower (P <.001), whereas the rate-corrected QT maximum (P =.04) and QT median (P =.06) were marginally higher in smokers than in nonsmokers. The spatial T amplitude was lower (P =.002), whereas the spatial QRS-T angle was higher (P =.01) in smokers compared with nonsmokers. Neither QT dispersion nor the slopes of the QT/RR and the spatial descriptors/RR regression equations differed between smokers and nonsmokers. CONCLUSIONS: Ventricular repolarization is altered in young male cigarette smokers. The differences in the heterogeneity of ventricular repolarization between smokers and nonsmokers are mainly due to heart rate differences between the 2 study groups.

Diagnosis of acute myocardial infarction in patients with chronic left bundle-branch block. Standard 12-lead ECG compared to dynamic vectorcardiography.

Standard 12-lead electrocardiogram (ECG) criteria were evaluated and compared with dynamic vectorcardiography for diagnosing acute myocardial infarction in 33 patients with chronic left bundle-branch block. In 14 patients a clinical diagnosis of acute myocardial infarction was made, but it was found that none of the seven most promising ECG criteria suggested in the literature could alone or in combination diagnose acute myocardial infarction. QRS vector difference evolution showed the same kind of pattern as that for patients with narrow QRS-complex. By using a predefined specific pattern, a diagnostic accuracy of 79% was achieved. The results indicate that dynamic vectorcardiography is a better tool for diagnosing and monitoring acute myocardial infarction in patients with left bundle-branch block than standard 12-lead ECGs taken on admission and after 12-24 h.

Continuous ST-segment monitoring during coronary angioplasty using orthogonal ECG leads.

In order to characterize ST-segment shifts during transient coronary artery occlusion, 24 patients with single-vessel disease were continuously monitored during percutaneous transluminal coronary angioplasty by use of a computerized orthogonal lead system. Changes of ST-segment (J + 60 ms) in leads X, Y, and Z and of the ST vector magnitude were analyzed by using 20 microV as a threshold for significant ST-segment shift. The sensitivity and magnitude of this shift were compared among the left anterior descending, right coronary, and circumflex artery groups (11, 8, and 5 patients, respectively) during balloon inflation. Significant ST-segment shifts were seen in 22 patients (92%) in ST-VM, Y, and Z leads and all patients in lead X (100%). There was no significant difference in sensitivity of either the ST vector magnitude or the most sensitive lead for occlusion detection among the three groups. There was a significantly greater magnitude of ST shift during left anterior descending artery occlusion than during right coronary artery and circumflex artery occlusions in ST-VM. Analysis of the direction of ST shifts in the X, Y, and Z leads showed a characteristic pattern, which could distinguish among the three coronary groups in 21 patients (88%). The presence of collaterals was significantly associated with ST-segment depression in leads oriented toward ischemia (3 of 6 patients) as compared with ST-segment elevation in the absence of collaterals (all of 15 patients), P > .01. It is concluded that ST-segment shift in the orthogonal leads is a reliable marker for myocardial ischemia. It is equally sensitive to occlusion of each of the three major coronary arteries and can thus identify the occluded coronary. An ST-segment depression instead of an elevation was related to the presence of collaterals, which may reflect a lesser degree of ischemia.

Non-invasive risk stratification within 48 h of hospital admission in patients with unstable coronary disease.

AIMS: In this study we evaluated the prognostic value of three methods of early risk estimation in patients with unstable coronary disease. METHODS AND RESULTS: The methods evaluated were: clinical risk estimation at hospital admission, continuous ST analysis with computerized vectorcardiography for 24 h and serial measurements of creatinine kinase-MB for 48 h. Twenty-seven (14%) of the 195 patients died or had a non-fatal infarction within one year. Clinical risk evaluation correctly identified a subgroup of patients with low risk but did not otherwise predict outcome. Fifty-six (29%) patients had ST vector magnitude episodes on vectorcardiography, 70 (38%) had three or more episodes of ST change vector magnitude and 74 (38%) had a peak creatinine kinase-MB value of 6 microgram.l-1 or more. The even rate for patients with ST vector magnitude episodes (23%) was significantly higher than for those without (10%; P < 0.05). For patients with and without three or more episodes of ST change vector magnitude the event rate was 23% and 9% respectively (P < 0.05) and for patients with and without creatinine kinase-MB > or = 6 microgram.l-1 the event rate was 23% and 8% respectively (P < 0.01). The positive predictive value of having none, either one or both of the ST or creatinine kinase-MB markers positive was incremental. CONCLUSION: Continuous vectorcardiographic monitoring of ischaemia in combination with serial creatinine kinase-MB measurement considerably improves risk stratification in unstable coronary disease.

[Analysis of vectorcardiogram (VCG) in 150 healthy pilots].

150 healthy male pilots, aged 22-46 years (31 +/- 5) were examined with the HBD-II A instrument. The results showed that vectorcardiogram (VCG) parameters of pilots were within the normal value by clinical diagnosis standard of VCG, but some indexes of VCG appeared different from the normal people, these might be the characteristics of VCG of pilots. The present study provided some new parameters of VCG such as P loop. The results of this study may be used for pilots selection and real-time medical monitoring for pilots on ground training.

Localisation of ventricular tachycardia substrates by analysis of the surface QRS recorded during ventricular tachycardia.

BACKGROUND: Analysis of the surface ECG can predict the locations of pacing foci but is of limited value for locating arrhythmogenic substrates causing ventricular tachycardia because of the effects of myocardial infarction, ischaemia, and bundle branch block on ventricular activation. AIM: To determine whether analysis of the initial 60 ms segment of the surface QRS improves the accuracy of the ECG for predicting ventricular tachycardia origin we correlated the locations of 37 arrhythmogenic areas present in 20 patients with the 3D vectors of the ventricular tachycardias generated by each respective area. METHODS: The 3D vector of each ventricular tachycardia morphology was calculated from the integrals of the initial 60 ms of the surface vectorcardiogram and from the entire QRS recorded in each lead of the Frank orthogonal lead vectorcardiogram. Sixty eight-morphologies of ventricular tachycardia were mapped using simultaneous recordings from 60 catheter electrodes. RESULTS: Ventricular tachycardias with 3D vectors directed inferiorly and posteriorly or superiorly and anteriorly were more likely to originate from the septum, P = 0.04, whereas tachycardias directed superiorly and to the right were more likely to originate from the inferior wall and the cardiac apex, P = 0.001. However, the same arrhythmogenic area could generate multiple ventricular tachycardias with different 3D vectors. In addition, ventricular tachycardias with similar 3D vectors were generated by arrhythmogenic areas in the septal, apical and inferior walls. The variances of the mean 3D vectors of ventricular tachycardias originating from each of 12 different cardiac regions were no different when based on the initial 60 ms of the surface QRS than on the entire surface QRS. CONCLUSION: Analysis of the surface ECG provides only an approximate guide to the locations of arrhythmogenic areas generating ventricular tachycardia even when analysis is restricted to the initial forces in the surface QRS. Therefore, detailed mapping is needed to accurately determine the number and location of arrhythmogenic areas.

DSP based enhanced data acquisition system.

Digital Signal Processing (DSP) based Enhanced Data Acquisition System for Electrocardiography/Verctorcardiography (ECG/VCG) has been developed. The system is based on Texas Instrument's TMS320C25 Digital Signal Processor which has the capability of executing 5 Million Instructions Per Second (MIPS) at peak speed. This processor provides the necessary requirements of parallel processing, instruction pipelining, execution of multiple instructions in a single clock cycle for real time data acquisition and analysis of Bio Signals. The present work describes the enhanced data acquisition system using DSP chip along with its peripherals.

[Anthropology and electrocardiography]. / Anthropologie und Elektrokardiographie.

Compared with the conventional ECG lead systems, the corrected orthogonal leads by Frank and the leads by Nelson constitute progress, especially if one considers their mathematical and physical comparability and the possibility of recording vectorcardiograms projected on to three orthogonal levels. The discussion about these lead systems and their application in infancy and childhood cannot be considered concluded; above all questions of their information content must be definitively clarified.