Search

Introduction Ventricular arrhythmias in Brugada syndrome (BrS) may be due to a combination of myocardial depolarization and repolarization abnormalities. The spatial QRS-T angle, measured by 3D ECG, reflects both myocardial depolarization and repolarization and has been proposed as a marker for sudden cardiac death risk in several cardiomyopathies. This marker has never been evaluated in BrS patients. Objective To evaluate the prognostic significance of the spatial QRS-T angle in patients with a spontaneous Brugada type 1 pattern (SBT1). Method 8 patients with a SBT1 were included (8 males, mean age 49.1 ± 10.9 years-old), 4 experienced sudden cardiac arrest or documented ventricular fibrillation (SCA/VF) at mean age of 38.8 ± 14.3 years-old. We analyzed conventional ECG and 3D ECG data using the CAVIAR method and compared data from VF/SCA group to other subjects. Results The spatial angle between the onset of the QRS and the T-wave loop (ODIR angle) was significantly higher in the SCA/VF group (49.1 ± 26.0 vs. 19.8 ± 3.8, P = 0.029). There was no significant difference between patients for conventional ECG measurements (PR interval 187.0 ± 29.6 ms in the SCA/VF group vs. 186.0 ± 38.7 ms, P = 1, QRS duration 130.0 ± 38.7 ms vs. 106.5 ± 12.5 ms, P = 0.30, corrected QT interval 471.8 ± 8.4 ms vs. 404.3 ± 45.1 ms, P = 0.057, Tpeak–Tend interval 115.5 ± 3.8 ms vs. 107.5 ± 34.7 ms, P = 1) ( Fig. 1 ). Conclusion The spatial angle between the onset of QRS and the T-wave loop appears to be significantly correlated with the risk of VF/SCD in BrS patients. A prospective study is needed to confirm these findings.

Background The standard 12-lead ECG remains one of the basic investigations for the early detection and assessment of acute coronary syndromes. It is easy to perform, anywhere and anytime, and can be digitally transmitted within minutes to an emergency medical service for remote advice and triage. But the conventional ST-segment deviation criteria are of limited diagnostic accuracy. The purpose of this study is to investigate how much the use of computerized ECG techniques based on the measurement of the serial spatiotemporal ECG changes could improve the detection accuracy of transmural myocardial ischemia. Methods We considered the serial changes of continuous 12-lead ECGs of 90 patients undergoing elective percutaneous coronary angioplasty (PTCA) recorded during balloon inflation as an experimental model of ECG changes induced by coronary artery occlusion. The spatiotemporal ECG changes were measured according to the CAVIAR method and assessed by multivariate discriminant analysis in reference to serial changes of control recordings and standard ECG criteria. Results The diagnostic accuracy of the CAVIAR criteria for ischemia detection was 97%, with sensitivity of 98% and specificity of 96%, whereas the diagnostic accuracy of the conventional ST-segment criteria was 74%, with sensitivity of 60% and specificity of 88%. The increase of overall performance was obtained for all the occlusion locations. Conclusions Computer-assisted quantitative serial ECG analysis, taking into account the spatiotemporal changes of the QRS and T waves, would provide the physician with additional information for significantly improving the detection of transmural myocardial ischemia.

Background and Purpose If only a standard electrocardiogram (ECG) is available, at least 25% of patients with long QT syndrome (LQTS) may be missed. Our goal is to quantify abnormal electrical activity and to develop an ECG decision rule for the patients with LQTS. Methods One hundred forty-one subjects were included in this study (71 patients with LQTS and 70 healthy subjects). A 12-lead digital ECG was recorded for each subject and analyzed using the CAVIAR (comparative analysis of ECG-VCG and their interpretation with auto-reference to the patient) method. Results A decision tree involving criteria based on 3 spatiotemporal ECG measurements—the QT interval and the maximum amplitude of the T wave, both corrected from heart rate, and the loss of planarity of the end of QRS—identified patients with LQTS from healthy subjects with a sensitivity of 89%, a specificity of 96%, and a total accuracy of 92%. Conclusions This study suggests that 3-dimensional ECG analysis may improve the detection of patients with LQTS.

Aim We sought to determine whether survivors of sudden death without structural heart disease have beat-to-beat electrocardiographic (ECG) characteristics at the microvolt and at the millisecond level that differ from normal subjects. Methods We studied patients at our implantable cardioverter defibrillator clinic who had been resuscitated from ventricular fibrillation with no evidence of underlying structural heart disease. Continuous 10-minute high-resolution unfiltered digital surface ECGs at 1000-Hz sampling rate were acquired in these subjects and in a group of healthy volunteers. We then analyzed different parameters of beat-to-beat variations in duration, amplitudes and vectors of the QRS complex, and the T wave using a locally developed program (Comparative Analysis of ECGs, Vectocardiograms, and their Interpretation with Auto-Reference to the patient) and compared them between the 2 groups. Results Thirteen patients (7 men; age, 46 ± 16 years) were studied. Standard ECGs were unremarkable in 7 patients and suggestive of Brugada syndrome in the 6 others. The control group consisted of 23 age- and sex-matched subjects (13 men; age, 41 ± 10 years). Although the QRS parameters showed only few differences between the 2 groups, there were several differences in parameters evaluating repolarization. Conclusion High-resolution ECGs show distinct beat-to-beat variations in parameters of repolarization in survivors of sudden death without structural heart disease, as compared with normal subjects. These findings may reflect increased electrical instability and should be evaluated for stratifying arrhythmic risk in asymptomatic individuals.

Despite many attempts to improve the management of acute myocardial infarction, only small trends to shorter time intervals before treatment have been reported. The self-care solution developed by the European EPI-MEDICS project (2001-2004) is a novel, very affordable, easy-to-use, portable, and intelligent Personal ECG Monitor (PEM) for the early detection of cardiac ischemia and arrhythmia that is able to record a professional-quality, 3-lead electrocardiogram (ECG) based on leads I, II, and V2; derive the missing leads of the standard 12-lead ECG (thanks to either a generic or a patient-specific transform), compare each ECG with a reference ECG by means of advanced neural network-based decision-making methods taking into account the serial ECG measurements and the patient risk factors and clinical data; and generate different levels of alarms and forward the alarm messages with the recorded ECGs and the patient's Personal electronic Health Record (PHR) to the relevant health care providers by means of a standard Bluetooth-enabled, GSM/GPRS-compatible mobile phone. The ECG records are SCP-ECG encoded and stored with the PHR on a secure personal SD Card embedded in the PEM device. The alarm messages and the PHR are XML encoded. Major alarm messages are automatically transmitted to the nearest emergency call center. Medium or minor alarms are sent on demand to a central PEM Alarm Web Server. Health professionals are informed by a Short Message Service. The PEM embeds itself a Web server to facilitate the reviewing and/or update of the PHR during a routine visit at the office of the general physician or cardiologist. Eighty PEM prototypes have been finalized and tested for several weeks on 697 citizens/patients in different clinical and self-care situations involving end users (188 patients), general physicians (10), and cardiologists (9). The clinical evaluation indicates that the EPI-MEDICS concept may save lives and is very valuable for prehospitalization triage.

In the current issue of the Journal, Klatsky et al (1) address the possible risk of chronically having “normal” electrocardiographic (ECG) changes that may mimic the presence of an acute myocardial infarction. The authors compare the rates of hospital admissions for various conditions, and outpatient cardiovascular diagnoses, in patients with early repolarization and controls. The presence of “normal” early repolarization changes on the ECG could indeed be misinterpreted as signs of an acute thrombotic occlusion of a coronary artery, and lead to inappropriate and even potentially harmful reperfusion therapy. Of the many people who present for emergency clinical evaluation with symptoms suggesting an acute coronary syndrome, only a small proportion have the thrombotic coronary occlusion for which immediate reperfusion therapy is indicated. The current European Society of Cardiology/American College of Cardiology guidelines suggest immediate reperfusion therapy only in patients with “ST elevation or presumably new left bundle branch block” (2). However, since ST elevation in the absence of myocardial infarction is common, the diagnostic threshold for such therapy yields low specificity. In the current paper, 30% of the subjects chronically had ST elevations 3 mm. Other studies (3,4) also indicate that ST elevation above the commonly accepted threshold is not unusual, particularly in young men. Thus an individual’s age and gender should also be considered. Both female gender and older age are associated with lower amplitudes of all ECG waveforms, including the ST segment (3). The phenomenon associated with “normal” ST elevation has been termed “early repolarization” and pertains to the absence of a truly isoelectric ST segment between the QRS complex of ventricular depolarization and the T wave of repolarization. The prevalence of early repolarization may be increased when the ST-segment changes are measured late after the J point, the heart rate is accelerated or there are conditions such as left ventricular hypertrophy or fascicular or bundle branch block that prolong the ventricular depolarization process (3). The findings by Klatsky et al (1) support previous reports of a high prevalence of early repolarization in young men of African descent (5– 8), and in persons who engage regularly in “vigorous” exercise (9,10). These findings also support the benign prognosis of this condition and even show nonsignificant trends toward lower use of health care. However, this study does not provide direct information on whether inappropriate and unnecessary therapy was administered as a result of misinterpretation of the early repolarization changes in patients who were admitted for in-hospital care. Because ST elevation due to early repolarization may be interpreted as changes due to myocardial infarction, several noninvasive and practical approaches can be taken to minimize misinterpretation. This editorial considers the use of new algorithms for computerized analysis of an individual ECG; observations of the “stability” of the ST-segment changes on serial ECGs; and other nonECG manifestations of ischemia, such as regional wall motion abnormalities assessed by echocardiography and myocardial perfusion defects via radionuclide measurements or contrast echocardiography.

Introduction: The aim of this study was to determine whether impaired adaptation of the QT interval to changes in heart rate predicts sudden death after an acute myocardial infarction. Methods and Results: The Groupe d'Etude du Pronostic de l'Infarctus du Myocarde (GREPI) trial was a prospective multicenter study designed to evaluate the long-term outcome of myocardial infarction. QT dynamicity was evaluated in 265 patients by analyzing 24-hour Holter recordings obtained 9 to 14 days after myocardial infarction. The linear regression slope of QT intervals measured to the apex and to the end of the T wave (QTe) plotted against RR intervals was calculated using a dedicated Holter algorithm. The value of QT/RR in predicting sudden death and total mortality was compared with those of ejection fraction, heart rate variability, and late potentials. Mean follow-up was 81 ± 27 months. There were 73 deaths, of which 23 were sudden. Of all the parameters, an increased diurnal QTe/RR slope (>0.18) was the strongest independent predictor of sudden death (relative risk 6.07, confidence interval 1.48–24.95,P = 0.01). Conclusion: Increased diurnal QTe dynamicity is independently predictive of sudden death among patients with myocardial infarction. This simple parameter may help to stratify risk and select patients who may benefit from antiarrhythmic prophylaxis.(J Cardiovasc Electrophysiol, Vol. 14, pp. 227-233, March 2003)

Hypermedia data browsing is a mean for improving information access. However, the overload and the heterogeneity of medical information, as well as the multitude of possible navigational paths, turn the consultation of data into a difficult task. We present in this paper a solution for the development of adaptive user interfaces in a hypermedia data browsing environment. It is based on the capitalization of the users knowledge in the decision-making process, expressed in terms of navigational paths and of data presentation modes that are customized to the user's preferences and practice. This capitalization offers the user a way to automatically store and reuse the experience accumulated in browsing through patient records. We illustrate our approach with the implementation of HEMA, a clinical workstation prototype that we have specialized for the cardiology domain.

Background Late potentials (LPs) in the terminal portion of the QRS complex are commonly sought to identify post-myocardial infarction patients prone to ventricular tachyarrthythmias (VT) or sudden death. More recent time–frequency signal processing tools have been shown to provide new parameters for the quantification of LPs and abnormal activities buried within the QRS complex. Methods and Results The study population comprised 23 myocardial infarction patients with documented sustained VT (MI+VT), 40 myocardial infarction patients without VT (MIVT) and 31 normal subjects. The reproducibility of the method was tested in an additional set of 66 patients. The signal-averaged high-resolution electrocardiograms (HRECGs) were quantified by deconstructing the unfiltered X, Y and Z leads using a 511-orthogonal wavelet network. Using receiver operating characteristics (ROC) curves and discriminant analysis applied to the wavelet coefficients, we extracted the most significant wavelets to classify the post MI patients. These wavelets detected time–frequency alterations both in the ST segment and within the QRS complex, characterizing patients prone to VTs. The same statistical methods were applied to the conventional time-domain measurements. The combined application in our population of the orthogonal wavelet deconstruction method and discriminant analysis had 91% sensitivity and 95% specificity, an improvement of 22% and 25%, respectively, compared with the conventional time–domain method. Reproducibility was 82%. Conclusions In post-myocardial infarction patients, orthogonal wavelet transforms can detect alterations in high-frequency components within the QRS and ST segment. Our findings support the view that waveletrelated parameters are more relevant than those of the time–domain method in predicting subsequent malignant tachyarrhythmias. (Europace 2000; 2: 141–153)

Introduction: QT dispersion assesses repolarization inhomogeneity on 12-lead standard ECG. However, the implications of the electrical cardiac vector during the repolarization phase (the T wave loop) with the genesis of this phenomenon are unknown. Methods and Results: The aim of this study was to explore conventional 12-lead resting ECG QT dispersion and the corresponding morphology of the spatial three-dimensional (3-D) T wave loop in 25 normals subjects, 30 postmyocardial infarction (Ml) patients, and in 17 individuals with congenital long QT syndrome (LQTS). Standard and XYZ ECG leads were simultaneously digitized (250 Hz) and automatically analyzed. Ventricular repolarization dispersion was estimated by the range (RAN12o) and standard deviation (SD12o) of the 12 rate corrected QTo intervals (between the Q wave onset and the T wave offset). Spatial T wave loops were extracted from XYZ data and analyzed with a 3-D algorithm which provides quantitative parameters related to the loop morphology. All scalar measurements of dispersion were significantly larger in the two pathological populations; however none of them could discriminate post-MI from LQTS groups (RAN12o = 33.3, 61.4, and 62.7 ms respectively, for the three populations). Conversely, a loss of planarity and an increased roundness of the T wave loop were observed in the two pathological groups, with the former effect more pronounced in the LQTS (P = 0.04 compared to post-MI) and the latter in the post-MI group (P = 0.02 compared to LQTS). Furthermore, multiple regression and principal component analyses showed that planarity and roundness are independently involved with QT dispersion. Conclusion: Changes in the morphology of the spatial T wave loop associated with QT dispersion were identified. These changes discriminate different substrates of repolarization inhomogeneity. The use of a 3-D technique to assess repolarization inhomogeneity may bring additional information on the intrinsic nature of this disorder.

Clinical centers are increasingly using new techniques such as Holter QT, late potential, and wavelet measurements. However, we lack validated databases for the assessment of the performance of the signal-processing methods and their reproducibility. Failure of the QT interval to adapt to changes in the heart rate is considered to be a more meaningful parameter than QT prolongation itself. In this study, different factors that may affect the reproducibility of QT and QTm (onset of the QRS to the maximum of T) measurement are analyzed: the incidence of sympathetic tone and parasympathetic activity on low- and high-frequency QT variability, the very low frequency dependency of the QT interval to changes in the R-R interval, changes in the heart's position, and measurement errors. Typical root-mean-square values of the beat-to-beat measurement errors in upright-position Holter recordings are only 1.5 ms for QT versus 3.4 ms for QTm. Although the dependence of the QT interval on the heart rate is well established, the method for rate correction of the QT interval remains controversial. None of the formulas for heart rate adjustment of the QT previously proposed provide complete correction for all of the rate influences involved due to "memory phenomenon"; that is, there is a time delay, ranging up to 3-4 minutes, between a change in heart rate and the subsequent change in the QT interval. This problem has been solved by developing patient-specific neural networks that are trained to "identify" the dynamic behavior of the QT interval (or QTm) as a function of the R-R interval in order to predict the beat-to-beat changes of the QT interval as a function of the measured beat-to-beat changes of the R-R interval. Computing the differences between the predicted and the measured QT interval will allow for the detection of any significant deviations, both in the steady-state and transient conditions. Recent developments in the analysis of the high-resolution electrocardiogram (HRECG) in the time domain and frequency domain, with emphasis on the assessment of the reproducibility of late potential and wavelet measurements, are also reported in this study. The two main causes of variability in HRECG analysis are physiology and, for time-domain analysis, intermanufacturer variability. Physiologic changes can be overcome by standardizing the clinical protocols and repeating the recordings. The most important technical requirement for the proper use of late potentials is to standardize the algorithm for the detection of QRS offset among different late potential analyzing machines so that clinical data can be exchanged. The recently introduced wavelet transform provides a fruitful alternative to the more classical time-domain methods. Preliminary results show an 8 to 15% performance improvement over conventional time-domain analysis for the stratification of the HRECG after myocardial infarction. Reproducibility is excellent, up to 100%, but needs to be assessed on larger populations matched for age, sex, and pathology.

The negative conduction effect of quinidine on each of the successive phases of the ventricular depolarization was investigated using an original noninvasive method: the spatial velocity electrocardio

Ventricular repolarization (VR) duration is an electrophysiologic parameter that is poorly explored in the conventional electrocardiogram. The heart rate (HR) and the autonomic nervous system (ANS) condition its variations. The static QT measurement in the surface electrocardiogram and its correction using the Bazett formula constitute inadequate tools. The three-dimensional Holter recordings and their computerized analysis are better adapted to assess the dynamicity of VR, a relevant image of the myocardial state. QT and RR values are linearly correlated over 24 hours, but this does not allow one to study specifically the respective roles of HR and ANS on repolarization changes. To do so, it is necessary to select appropriately the QRST complexes according to their environment: not only the last RR cycle but the mean HR over the preceding minutes, and the circadian influences must be controlled to differentiate the role of the short- and long-term influences. Combining the ATREC and the CAVIAR softwares now permits control of both time and space dimensions and to measurement of the QT variations with a precision of the order of 1 ms, a performance necessary to assess tiny but meaningful changes. The QT interval is shorter, and the slope of the QT/RR regression line is steeper at daytime compared with night, and many situations modify this normal behavior. Aging lengthens the QT interval and reduces the day-to-night differences of QT duration and dynamicity. In contrast with duration, dynamicity does not depend on gender. Any heart disease, left ventricular hypertrophy, or heart failure alter QT dynamicity. In the long QT syndrome, the changes in dynamicity are probably in essence more specific markers than the QT duration itself. The drug action also is detectable, with particular reference to the reverse use-dependence of the type III effects. On the condition to use a rather sophisticated technical approach, studying the VR behavior yields a direct investigation on the state of the ventricular myocardium and its dependence on the HR and the ANS.

International audience; 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.

Computer programs for the interpretation of electrocardiograms (ECGs) are now widely used. However, a systematic assessment of various computer programs for the interpretation of ECGs has not been performed.We undertook a large international study to compare the performance of nine electrocardiographic computer programs with that of eight cardiologists in interpreting ECGs in 1220 clinically validated cases of various cardiac disorders. ECGs from the following groups were included in the sample: control patients (n = 382); patients with left ventricular hypertrophy (n = 183), right ventricular hypertrophy (n = 55), or biventricular hypertrophy (n = 53); patients with anterior myocardial infarction (n = 170), inferior myocardial infarction (n = 273), or combined myocardial infarction (n = 73); and patients with combined infarction and hypertrophy (n = 31). The interpretations of the computer programs and the cardiologists were compared with the clinical diagnoses made independently of the ECGs, and the computer interpretations were compared with those of the cardiologists.The percentage of ECGs correctly classified by the computer programs (median, 91.3 percent) was lower than that of the cardiologists (median, 96.0 percent; P less than 0.01). The median sensitivity of the computer programs was also significantly lower than that of the cardiologists in diagnosing left ventricular hypertrophy (56.6 percent vs. 63.9 percent, P less than 0.02), right ventricular hypertrophy (31.8 percent vs. 46.6 percent, P less than 0.01), anterior myocardial infarction (77.1 percent vs. 84.9 percent, P less than 0.001), and inferior myocardial infarction (58.8 percent vs. 71.7 percent, P less than 0.0001). The median total accuracy level (the percentage of correct classifications) was 6.6 percent lower for the computer programs (69.7 percent) than for the cardiologists (76.3 percent; P less than 0.001). However, the performance of the best programs nearly matched that of the most accurate cardiologists.Our study shows that some but not all computer programs for the interpretation of ECGs perform almost as well as cardiologists in identifying seven major cardiac disorders.

The congenital Long QT Syndrome (LQTS) is an inherited disorder of ventricular repolarization that predisposes affected individuals to sudden death. The analysis of conventional ECG may be misleading, and we need non invasive markers to identify more accurately patients with rhese conditions. In the LQn syndrome, the fast-deluyed rectifier current Ikr is altered and leads tu a prolonged Action Potential Duration (APD) in midmyocardial areas that in turn translates to a prolonged QT interval and a widened T-wave. The aim of this work was to find new ECG parameters which can be used to identify LQ72 curriers in a large population. The study population was composed of 67 normal healthy subjects and I1 known carriers of U HERG mutation flour dierenr mutations and four families). For each subject a 12-lead digital ECG was recorded and analyzed by using the spatiotemporal CAVIAR method. With only one single CAVIAR measurement we could correctly classify 93.6% of the cases. This measurement, called UDIR, represents the diference in orientation between the T wave and the beginning of QRS. Its values are significantly higher in the Le72 patients (mGD±58.5° /spl plusmn14.5°) than in the normal population (m&SD±21.6° ±14.6°)with a pvalue< 1OE-9. This study demonstrates that it could be possible to identlB potential LQn carriers by analyzing spatiotemporal ECG waveform patterns of a conventional 12 -lead ECG.

Introduction Studies evaluating changes in HRV preceding the onset of ventricular arrhythmias using conventional techniques have shown inconsistent results. Time-frequency analysis of HRV is traditionally performed using short-term Fourier transform (STFT). Wavelet transform (WT) may however be better suited for analyzing non-stationary signals such as heart rate recordings. Methods and results We studied patients with a history of myocardial infarction implanted with a defibrillator with an extended memory. The RR intervals during the 51 min preceding ventricular events requiring electrical therapy were retrieved, and HRV studied by WT and STFT. 111 episodes of ventricular arrhythmia were retrieved from 41 patients (38 males, age 64±8 years). Heart rate increased significantly before arrhythmia. There was no significant variation in low frequency / high frequency components (LF/HF) observed for the group as a whole, probably due to a great degree of heterogeneity amongst individuals. A subset of 30 patients also had heart rate recordings performed during normal ICD follow-up. WT did not show any difference in HRV before arrhythmia onset and during control conditions. Conclusion Variations in HRV before onset of ventricular arrhythmias were not apparent in this large dataset, despite use of optimal tools for studying time-frequency analysis.

International audience; An operational e-health infrastructure including pervasive services and remote distributed applications servers in the cardiology domain is presented. Based on the implementation of previously reported software components building blocks, developed in particular within the frame of European projects, the architecture promotes and facilitates the use of advanced methods of quantitative electrocardiology. The expected outcome is the improvement of the early detection of cardiac diseases, of the patients follow-up and the enhancement of the citizens quality of life.

The authors present a new method for quantitatively assessing the spatiotemporal information content of pseudo-orthogonal Holter recordings. Based on the CAVIAR serial electrocardiogram/vectorcardiogram analysis method, it allows precise measurement of both beat-to-beat morphology and time-interval changes in standard, three-channel analog ambulatory electrocardiogram recordings. All measurements are automatically corrected for delineation errors or changes in the position of the heart. The method has been tested on Holter recordings of head-up tilt tests performed on 22 healthy subjects under controlled breathing: 10 min in supine and 10 min in 90 degrees upright tilt position. Spectral analysis clearly identified spectral events in the QT interval, with very low residual noise, and a significant increase of the QT low-frequency components in the upright tilt position. >

Detection of QT dispersion on a 12 lead surface electrocardiogram has been proved to be a strong prognostic index of malignant events and it is thought to be closely related to an heterogeneity in the repolarization wavefront This work aims to correlate QT dispersion with the morphology of the spatial T wave loop. Indexes of planarity and geometry are derived from the 3D-ECG repolarization loop with a validated algorithm (CAVIAR). Multiple regression analysis indicates that QT dispersion measured on 12 standard lead is significantly correlated with a loss of planarity and with a wider shape of the loop. QT dispersion is then closely related to a spatial distortion of the cardiac vector during the repolarization phase and can be indirectly evaluated on the 3D electrocardiogram.

The aim of this paper is to validate wavelet analysis of Holter recordings as a tool for the detection of risk of sudden cardiac death for patients surviving an acute myocardial infarction. The study uses time-averaged HR-ECGs from the European Myocardial Infarct Amiodarone Trial (EMIAT). Each HR-ECG is transformed into 511 orthogonal Meyer wavelet coefficients, extending from 128 ms before to 384 ms after QRS onset, and their value is assessed by means of the CARTEF Time-Frequency Abnormalities Stratification method. We then perform a linear discriminant analysis to assess the discriminant power of all wavelet coefficients with a significant p-value (p

The QT interval measured on the body-surface Electrocardiogram (ECG), corresponds to the time elapsed between the depolarization of the first myocardial ventricular cell (beginning of the Q wave) and the end of the repolarisation of the last ventricular cell (end of the T wave). Abnormalities in the adaptation of the QT interval to changes in heart rate may facilitate the development of ventricular arrhythmia. None of the formulas previously proposed for the adjustment of QT for changes in heart rate provide satisfactory correction. This is due to the "memory phenomenon" (i.e. time delay) ranging up to 3-4 minutes, between a change in heart rate and the subsequent change in the QT interval. In this paper, patient specific predictive models based on a Multi Layer Perceptron are presented and their predictive performance is tested on real and artificial data.

The QT interval measured on the body-surface Electrocardiogram (ECG), corresponds to the time elapsed between the depolarization of the first myocardial ventricular cell (beginning of the Q wave) and the end of the repolarisation of the last ventricular cell (end of the T wave). Predictive models of the QT dynamical behavior are believed to be a useful tool to detect abnormalities in QT adaptation for heart rate changes. In this paper, patient specific predictive models based on a Multi Layer Perceptrons are presented and their predictive performances are tested on real and artificial data.

Summary. An important part of an electrocardiogram (ECG) interpretation is the comparison between the present ECG and earlier recordings. The purpose of the present study was to evaluate a combination of two computer-based methods, synthesized vectorcardiogram (VCG) and CAVIAR, in this comparison. The methods were applied to a group of 38 normal subjects and to a group of 36 patients treated with anthracyclines. A fraction of these patients are likely to develop cardiac injury during or after the treatment, since anthracyclines are known to cause heart failure and cardiomyopathy. Two ECGs were recorded on each patient, one before and one after the treatment. On each normal subject, two ECGs were recorded with an interval of 8–9 years. A synthesized VCG was calculated from each ECG and the two synthesized VCGs from each subject were analysed with the CAVIAR method. The CAVIAR analysis is a quantitative method and normal limits for four measurements were established using the normal group. Values above these limits were more frequent in the patient group than in the normal group. The conventional ECGs were also analysed visually by an experienced ECG interpreter without knowledge of the result of the CAVIAR analysis. No significant serial changes were found in 10 of the patients with high CAVIAR values. Changes in the ECGs were found in two patients with normal CAVIAR values. In summary, synthesized VCG and CAVIAR could be used to highlight small serial changes that are difficult to find in a visual analysis of ECGs.

An almost perfect planarity of the spatial QRS loop is known as a characteristic of normal hearts. The Lyon VCG program routinely computes an original planarity index based on the relative magnitude of a so-called geometrical area vector (GAV%). It provides an indirect assessment of any kind of loop distortion (distorted segments lying outside the preferential plane, concavities, figures of eight, narrow configuration). Mean intraindividual variations of GAV%, studied in three different conditions, showed its relatively good stability. Eleven groups totaling 1,435 subjects were investigated. The highest GAV% values (mean, 88%) and the smallest scatter (sigma = 7) were found in normal tracings. GAV% was lower in right (mean, 82%) and left (76-82%) ventricular hypertrophies, in inferior (82%) and anterior (61%) myocardial infarctions, and in right (55%) and left (49%) bundle branch blocks. The diagnostic value of this index was tested for the normal-abnormal discrimination. Using a threshold of 80%, specificity was 89.6%, sensitivity was 78.6% for anterior myocardial infarction, right BBB was 86.6%, left BBB was 91.0% and other groups had unsatisfactory sensitivity. Poor correlations were observed with six other structural parameters, demonstrating that GAV% is relatively independent and may provide new diagnostic information.

have also been shown to be elevated in patients with non-postoperative atrial arrhythmias, specifically atrial fibrillation (AF). We postulated that a high CRP level would predict AF recurrence in patients on antiarrhylhmic drugs (AAD). Methods and results: One hundred and fifty seven patients who had undergone direct current cardioversion for AF between November 2001 and June 2002 were identified (Tablel). All had CRP levels drawn prior to the procedure. All these patients had been on AAD prior to and following cardioversion. All patients were followed in our out patient clinic.109 patients had recurrence of AF and 48 patients did not have recurrence of AF and responded to AAD. Using the Mann-Whitney nonparametric test the mean hsCRP level in the group with recurrence was 0.642 which was statistically higher than the group with no recurrence 0.264 (p-valuec0.001). Only left ventricular ejection fraction (LVEF) was related to hsCRP in multivariate analysis, however LVEF was not statistically different between both groups. The odds ratio of developing recurrence was 9 with every 0.5 unit increase over 0.554 (pvalue