bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absence of Gender Difference in Circadian Trends of QT Interval Duration
Authors: Anselme Frédéric , Maison‐Blanche Pierre , Cheruy Pascale , Saoudi Nadir , Letac Brice , Coumel Philippe 
Published: October 2006

Background: The long‐term circadian behavior of the QT interval duration was comparatively evaluated in females and in males. The corrected QT interval duration is known to be longer in females than in males, and this gender difference persists after double autonomic blockade.Methods: Our population consisted of 32 young healthy subjects (16 males). Twenty‐four‐hour ambulatory ECG recordings were processed by QT analysis software. All sinus complexes were averaged on a 30‐second time basis. The averaged template was defined by a single QT apex (QTa) interval and its mean RR interval. The circadian behavior of ventricular repolarization was assessed by the nocturnal lengthening of QTa at an identical RR interval, and by the respective diurnal and nocturnal QT/AR relationship in both genders.Results: The corrected QTa was longer in females (318 ± 20 vs 294 ± 13 ms, P = 0.0003). The correlation coefficients of the QTa/RR regression lines were >0.75, whatever the gender and the circadian period considered. In both genders, diurnal slopes were higher than nocturnal ones (0.15 ± 0.01 vs 0.09 ± 0.03 in males and 0.18 ± 0.04 vs 0.09 ± 0.05, P = NS), and the nocturnal lengthening of QTa was on the same range (25 ± 12 vs 17 ± 12 ms, P = NS).Conclusion: The longer corrected QT interval in females is not associated with a specific static or dynamic circadian behavior of QT interval.
Evaluation of Outpatient Arrhythmias and Pacemakers Utilizing Transtelephonic Monitoring Devices
Authors: Dubner Sergio , Sztyglic Elena , Boskis Pablo , Roa Graciela , Boskis Bernardo 
Published: October 2006

Background: The purpose of this trial was to evaluate a patient actuated transtelephonic cardiac monitoring system in order to document cardiac arrhythmias and cardiac pacemaker function.Material: Eighty‐two patients were prospectively evaluated, 69 with pacemaker (group I) and 13 with symptomatic arrhythmias (group II). Two different recorders were used: a memory loop‐recorder (KH) and a wrist‐worn recorder (HW). Both of them were implemented using a small, portable, battery‐powered transmitter, which monitors a modified V5 in KH and a lead 1 with the HW over regular nondigital pulse telephone lines.Results: In group I, 54 patients used single chamber pacemakers, 2 VDDR, and 13 used dual chamber devices. In group II, all patients included referred palpitations as their symptom. In group I, 248 registers were made using the KH and 50 with the HW. Recordings were made with KH had a 96% accuracy in the diagnosis of the ECG, while HW recordings failed to detect the QRS and the spike in 52% of the cases. Arrhythmia patients (group II) made 65 recordings with KH, all symptomatic: 28 were ventricular ectopic beats (23 isolated, 4 bigeminy, and 1 coupled ventricular ectopic beats); 9 supraventricular ectopic beats (isolated); 18 episodes of sinus tachycardia; and 10 normal sinus rhythm. Artifact was present partially in 6 other recordings, but did not affect the diagnosis. Two patients made no recordings and were excluded from the trial (group I).Conclusions: The loop‐recording transtelephonic monitoring system is an excellent tool for the evaluation of patients with symptomatic arrhythmias and pacemaker. The memory KH had an excellent performance, even over regular telephone lines. The accuracy of the HW recordings was low and failed to evaluate the QRS, probably due to the direction of the AQRS vector.
Relationship Between Heart Rate Variability and Cardiovascular Risk Factors in Middle‐Aged Males
Authors: Pikkujämsä Sirkku M. , Huikuri Heikki V. , Ikäheimo Markku J. , Airaksinen K. E. Juhani , Rantala Asko O. , Lilja Mauno , Savolainen Markku J. , Reunanen Antti , Kesäniemi Y. Antero 
Published: October 2006

Background: Abnormal autonomic control of heart rate is associated with an inreased risk of cardiovascular morbidity and mortality. There are few population‐based reports on the interindividual variation and determinants of cardiac control in healthy middle‐aged males.Methods: Autonomic modulation of heart rate was studied in 172 randomly selected middle‐aged males (mean age 50 ± 6 years) by measuring the heart rate variability (HRV), which was related to life style data, personality type, blood pressure, lipid analyses, results of the 2‐hour glucose tolerance test and left ventricular function.Results: Large interindividual variation was observed in the standard deviation of RR intervals (mean 59 ± 20 ms; coefficient of variation (CV) 34%) compared to variation of the average heart rate (mean 76 ± 11 beats/min, CV 14%). When analyzed as normalized units, marked interindividual variation was observed in the low (CV 16%) and high frequency component (CV 37%). The total power of HRV had significant indirect univariate correlations with age, blood pressure, body mass index, 2‐hour blood glucose level, fasting and 2‐hour serum insulin levels, triglyceride level, and a direct correlation with left ventricular fractional shortening. In a multiple regression analysis, the total power of HRV was best predicted by age (β=−0.27, P = 0.0002), followed by the fractional shortening (β= 0.25, P = 0.0004), systolic blood pressure (/3 =−0.2 1, P = 0.005) and 2‐hour insulin level (β=−0. 9, P = 0.01).Conclusions: Overall HRV has a wide interindividual variation and is related to several cardiovascular risk factors, perhaps contributing to the observed association between low HRV and cardiovascular mortality. Normalized units of HRV reflecting sympathovagal balance are unrelated to age, life style, or cardiovascular risk factors.
The Signal‐Averaged ECG Obtained by a New Digital Holter Recording System
Authors: Schneider Michael A. E. , Plewan Andreas , Schmitt Claus , Meinertz Thomas 
Published: October 2006

Background: The implementation of signal‐averaged analysis in the Holter recording may increase cost‐effectiveness and enables further insights into pathophysiological links between arrhythmia genesis and time related modulating factors. This study assesses the feasibility of a new digitizing long‐term recorder system to perform a signal‐averaged analysis and compares the data with the results achieved by an established bedside real‐time recording system.Methods: The study was performed prospectively in 22 patients. The digital recorder FD‐3 obtained a 3‐channel 24‐hour Holter monitoring. For the signal‐averaged ECG analysis, a template averaging was achieved in 5‐minute periods. The interpolated sampling rate was 1024 Hz. The signal‐averaged ECG by bedside real‐time system was performed using the Predictor system. At 25–250 Hz and 40–250 Hz band‐pass filter, 4 FD‐3 epochs acquired in a 6‐hour interval were chosen and the mean values of QRS, root mean square (RMS), and low amplitude signal (LAS) were compared with the data obtained by one Predictor measurement.Results: The regression analysis shows a positive correlation between the FD‐3 and Predictor data of QRS, RMS, and LAS at both filter settings except for LAS at 25–250 Hz. Regarding the late potential classification, at 25–250 Hz 4 of 22 (18%) FD‐3 and Predictor classifications were not coherent and at 40–250 Hz only 2 of 22 (9%) classifications did not correlate.Conclusions: The FD‐3 recorder is feasible to perform a signal‐averaged ECG analysis. Especially at 40–250 Hz, the late potential classification shows a concordant distribution.
Localization of Myocardial Infarction Based on Learning Vector Quantization Networks Applied to ST Elevations of the 12‐Lead ECG
Authors: Reinhardt Lutz , Vesanto Riikka , Montonen Juha , Fetsch Thomas , Mäkijärvi Markku , Sierra Gilberto , Katila Toivo , Breithardt Günter 
Published: October 2006

BackgroundDuring recent years artificial neural networks have been proposed as a diagnostic tool in different fields of cardiology. Most of the studies have utilized the multilayer perceptron with backpropagation learning rule for the design of the network. As a new approach, Learning Vector Quantization (LVQ) which belongs to the class of competitive learning networks, was developed particularly for classification problems. So far there are no data available on the application of LVQ for classification tasks in cardiology. The present study aims at investigating the performance of LVQ for localization of myocardial infarction (Ml) based on ST elevations in the standard 12‐lead ECG.MethodsAltogether, 769 male patients (age 53 ± 7 years) with an acute Ml were included into the study. Three hundred fifty‐three patients (46%) presented with anterior and 416 patients (54%) with inferior Ml based on typical changes in the standard 12‐lead ECG. Standardized ST elevations in all 12 leads were used as input structure for the network. The performance of the network was studied using two different learning and test sets. The influence of the number of reference vectors and training steps on the classification accuracy for infarct location was investigated.ResultsThe highest classification accuracy of 88.6% for infarct location was achieved using the learning set with 66% of all patients. This setup was based on five reference vectors and 200 training steps. The best accuracies for anterior Ml were higher as compared to inferior infarctions in both the test and training set. Using more than 50 reference vectors resulted in a decrease of classification accuracy due to overtraining of the network.ConclusionAppropriately initialized and trained artificial neural networks based on LVQ give a high accuracy for localization of Ml using only ST elevations of the standard 12‐lead ECG.
Quantification of Prevalence of Asymptomatic Ventricular Arrhythmias in Patients with Heart Failure
Authors: Anastasiou‐Nana Maria I. , Menlove Ronald L. , Mason Jay W. 
Published: October 2006

BackgroundVentricular arrhythmias (VAs) are recorded in many patients with chronic heart failure. The present study was designed to prospectively determine and quantify the prevalence of asymptomatic VAs in this patient population.MethodsOne hundred and two patients, 82 men and 20 women (median age 61 years) with NYHA Functional Class II (n = 50, 49%) and III (n = 52, 51%) heart failure were prospectively assessed with 24‐hour ambulatory ECGs.ResultsRare premature ventricular complexes (PVCs) (<100/24 hours) were observed in 22 (21.6%), moderately frequent (101–1000/24 hours) in 31(30.4%), and frequent (>1000/24 hours) in 49 (48.0%) patients. A significantly greater prevalence of <100 PVCs/24 hours was observed in male compared to female patients (P < 0.03) and in those over 61‐years old compared to younger patients (P < 0.01). There was a significantly greater incidence of >0 repetitive PVCs (RPVCs) per 24 hours and >25 RPVCs/24 hours in patients with low ejection fraction (EF), defined as either ≤0.30 (P = 0.003) or ≤ 0.22 (P = 0.02). The occurrence of VT events was significantly associated with EF ≤ 0.30 (P = 0.007). The prevalence of >100 PVCs/24 hours was significantly higher in patients treated with digoxin (P < 0.02).ConclusionsPVCs are more frequently observed and more frequent in number in patients with heart failure than in normal subjects, and arrhythmia severity correlates with severity of left ventricular dysfunction.
Functional Late Potential Analysis With Exercise Testing to Identify Patients Prone to Ventricular Tachycardia After Myocardial Infarction
Authors: Steinbigler Peter , Haberl Ralph , Schmücking Ingo , Dorwarth Uwe , Mattke Sören , Hoffmann Ellen , Steinbeck Gerhard 
Published: October 2006

Objective: Exercise induced ischemia or heart rate acceleration may unmask late potentials or provoke functional changes, which might be important factors to improve the low positive predictive value of late potential analysis at rest for postinfarction risk stratification. However, methodological refinements are required to detect late potentials with exercise.Methods: We, therefore, investigated the surface‐electrocardiogram in 100 patients after myocardial infarction (50 with sustained ventricular tachycardia [group I], 50 patients without ventricular arrhythmias [group II], and in 15 normals before and immediately after bicycle exercise test using Spectrotemporal Mapping (STM) with fast Fourier transform (FFT) and Simson method and introduced selective signal averaging.Results: In group I, 30 out of 50 patients showed late potentials at rest, after selective signal averaging also recognizable immediately after exercise in all of these patients, however, with a time‐shift of 18 ± 13 ms into the ST‐segment. Twelve out of 50 patients of group I with only transient late potentials tended to have inducible and recurrent ventricular tachycardia with a shorter cycle length. In group II, 4 out of 50 patients had late potentials at rest and 2 out of 46 patients developed them during exercise. Transient pathological Simson method was associated with transmural ischemia.Conclusions: Thus, detection of the effects of exercise on late potential analysis is possible with selective signal averaging immediately after exercise. Exercise unmasks late potentials not detectable at rest by their time‐shift into the ST‐segment. Using this method, patients that would have been lost with conventional late potential analysis, could be identified.
Late Potentials in Healthy Subjects
Authors: Toft Jens , Rasmussen Verner , Hesse Birger , Au Samir , Carstensen Steen , Jensen Gorm 
Published: October 2006

Objective: Criteria for detection of late potentials have not yet been standardized, but the criteria recommended by ESC/AHA/ACC are widely used. In this investigation, the prevalence of late potentials is studied in an age stratified healthy population with likelihood of coronary artery disease < 5%. Relation between signal‐averaged variables and clinical variables was studied.Methods: Signal‐averaged ECGs were recorded using Butterworth filters at 40 and 250 Hz. The following three time‐domain parameters were evaluated: QRS duration (duration of the amplified, filtered QRS complex); LPD (duration of the late potentials, i.e., duration from the point of time when the magnitude of the main complex becomes lower than 40 μV); and RMS40 (root mean square of the activity within the last 40 ms of the amplified, filtered QRS complex).Results: QRS duration was significantly longer in men than in women, and was correlated to the mass of the left ventricle (LVM). The combination LPD and RMS40 gave the highest prevalence of late potentials. The prevalence of late potentials was 25%.Conclusion: Standard criteria should be used with great caution, and normal limits should be established in each laboratory to a preselected noise level. QRSD should be included within the definition of reference limits and should be gender matched. Even though there is correlation between LVM and the QRSD, the upper normal limit of QRSD based on LVM matching is unchanged.
Cross Spectral Analysis in Assessment of Baroreflex Gain in Patients with Coronary Artery Disease
Authors: Airaksinen K.E. Juhani , Tahvanainen Kari U.O. , Kuusela Tom A. , Huikuri Heikki V. , Niemelä Matti J. , Karjalainen Pasi , Eckberg Dwain L. 
Published: October 2006

Background: Interest in determination of baroreflex sensitivity in clinical practice is growing because of its prognostic information in patients with heart disease. The purpose of the present study was to assess the feasibility of cross spectral analysis in the determination of baroreflex gain from spontaneous RR interval and systolic pressure fluctuations, and to compare the results to the traditional pharmacological method in patients with coronary artery disease.Methods: We measured the gain and time lag between RR interval and systolic pressure variabilities in the frequency domain, and compared baroreflex indexes obtained by this technique with standard phenylephrine tests in 32 patients with coronary artery disease.Results: Cross spectral analysis by fast Fourier transform techniques yielded acceptable (> 0.5) coherence between systolic pressure and RR interval in the mid‐ (0.07–0.15 Hz) and in the respiratory‐frequency (0.15–0.40 Hz) band fluctuations in 30 patients (94%), with mean coherences of 0.69 and 0.74. The mean phase difference in the mid‐frequency band was greater than in the respiratory‐frequency band (−83 vs −23 degrees, P < 0.001), suggesting that the mid‐frequency fluctuations of RR intervals followed nearly 2 seconds after pressure changes, while respiratory‐frequency fluctuations of RR intervals occurred nearly concomitantly with systolic pressure. The mean baroreflex slope derived from the bolus phenylephrine technique was 6.2 ms/mmHg (range 1.6–16.0), 5 patients had an abnormally low (< 3 ms/mmHg) baroreflex sensitivity. Baroreflex gain determined by cross spectral analysis from the mid‐frequency band correlated significantly (r = 0.60, P < 0.001, n = 27) with the baroreflex gain determined by the phenylephrine test, while the correlation in the respiratory‐frequency band was not significant (r = 0.35, P = 0.09, n = 26).Conclusions: Baroreflex slopes derived from cross spectral techniques provide reliable (but not perfect) information regarding baroreflex gain derived from the classic phenylephrine technique, even in patients with depressed baroreflex responses. Cross correlation calculation of spontaneous baroreflex slopes should be limited to data in the mid‐frequency range, where the slopes are likely to reflect simple baroreflex physiology.
Effect of Low‐Dose Scopolamine on Autonomic Control of the Heart
Authors: Raeder Ernst A. , Stys Adam , Cohen Richard J. 
Published: October 2006

Background: In low doses, scopolamine paradoxically enhances parasympathetic outflow to the heart. The mechanisms which mediate this action are not fully understood. Moreover, there are conflicting data regarding the potential role of sympathetic activity. This study in 17 healthy individuals was designed to characterize the influence of low dose transdermal scopolamine on the gain of the baroreflex and respiratory heart rate reflex and to determine the role of sympathetic activity.Methods: The effect of scopolamine was analyzed in the time and frequency domain by computing heart rate variability indices. The gains of the respiratory heart rate reflex and the baroreflex were estimated simultaneously by means of a cardiovascular system identification approach using an optimized autoregressive moving average algorithm. Measurements were repeated in the upright posture to assess the influence of enhanced sympathetic activity. In six subjects ambulatory ECGs were recorded to determine whether there are diurnal variations of the effect of scopolamine.Results: Scopolamine enhances vagal modulation of heart rate through both the respiratory‐heart rate reflex and the baroreflex, as the gains of both were augmented by the drug in the supine and in the upright postures.Conclusions: Scopolamine increases parasympathetic cardiac control by augmenting the gain of the respiratory‐heart rate and baroreflex. This action is not attenuated in the upright posture when sympathetic tone is increased.
Association Between Parasympathetic Activity and Late Potentials at Low Noise Level
Authors: Christiansen Evald Høj , Frost Lars , Mølgaard Henning , Nielsen Torsten Toftegaard , Pedersen Anders Kirstein 
Published: October 2006

Background: Late potentials (LP) in the signal‐averaged ECG represent activation of myocardial areas with slow conduction and predicts re‐entrant malignant ventricular arrhythmias in coronary artery disease. Low heart rate variability, which reflects low vagal and concomitantly elevated sympathetic activation also predicts ventricular arrhythmia. This autonomic profile is associated with the presence of LP (detected at noise level 0.4 μ;V) early after myocardial infarction. In contrast, sympathetic stimulation and diminution of vagal tone influence LP parameters (detected at noise level 0.2 μ;V) in the opposite direction in healthy subjects. The aim of this study was to estimate the possible association between measures of cardiac autonomic function and LP (detected at 0.4 and 0.2 μ;V) in patients with chronic coronary artery disease.Methods: ECGs of 174 consecutive patients with angiographically documented coronary artery disease and without myocardial infarction during the last 3 months were signal‐averaged to noise level 0.2 and 0.4 μ;V. LP were considered to be present if any two of the following criteria were present: signal‐averaged QRS duration > 120 ms, root‐mean‐square voltage of the terminal 40 ms of the averaged QRS complex < 25 μ;V, and late potential duration > 40 ms. Heart rate variability was measured at rest in 5‐minute ECG recordings as: the standard deviation (SD) of all RR intervals, SD corrected for RR (SD/mean RR), and the power of high frequency (HF) component (0.15–0.40 Hz).Results: One hundred seven (61%) of the patients had LP at noise level 0.2 μ;V. LPs were more frequently observed in patients with slow heart rate, high heart rate variability, and high levels of vagal activity (mean RR >; 1000 ms, SD >; 60 ms, and HF >; 100 ms2) than in patients with higher heart rate, low heart rate variability and attenuated vagal activity: 73% vs 54% (P = 0.02), 71% vs 53% (P = 0.02), 72% vs 51% (P = 0.005) for mean RR, SD, and HF power, respectively. Adjustment for possible confounding from mean RR level, gender, previous acute myocardial infarction, treatment with betablocker, and left ventricular ejection fraction did not significantly alter these associations. At noise level 0.4 μ;V 26% (45/174) had LP and the diagnosis of LP was not significantly associated with heart rate variability.Conclusions: At low noise level (0.2 μ;V) higher parasympathetic activity is associated with the diagnosis of LP. The predictive power of presence of LP diagnosed at low noise level for development of sudden cardiac death may be reduced by this association. In order to increase the predictive accuracy of LP we recommend either the use of noise level 0.4 μ;V, or identification of high arrhythmia‐risk patients by a combination of the presence LP and impaired heart rate variability. However, a prognostic study is needed to further clarify this.
Provocative Testing in Children with Suspect Congenital Long QT Syndrome
Authors: Berul Charles I. , Sweeten Tammy L. , Hill Sharon L. , Vetter Victoria L. 
Published: October 2006

ObjectivesThis study was designed to evaluate several alternative ECG measurements and provocative tests in order to identify markers for children with suspect congenital long QT syndrome (LQTS).BackgroundA single QTc measurement on a resting ECG does not identify all children with LQTS. Alternative ECG measurements have been established for identification of LQTS patients, with varied degrees of accuracy. Additionally, findings of QT prolongation during exercise or catecholaminergic stimulation have been suggested as indicators for the presence of LQTS and associated arrhythmias.MethodsThe ECGs from 40 children with suspect congenital LQTS were compared with 1000 gender and age matched control patients. Complete exercise ECG studies were performed on 32 of the 40 suspect LQTS patients and compared with 29 controls. ECGs recorded during isoproterenol infusion were obtained in 9 suspect LQTS patients and compared with 44 matched control subjects.ResultsDuring exercise, the QTc was mildly prolonged in both groups, without a similar increase in JTc, suggesting prolongation of depolarization time. QT and JT dispersion shortened with exercise in control subjects, but not in the suspect LQTS patients. During isoproterenol infusion, the QTc and JTc are prolonged in the suspect LQTS group, without an increase in the control patients.ConclusionsWe describe the ECG findings with provocative testing in patients in whom there is a clinical suspicion of LQTS, yet have a normal or borderline QTc. Exercise or isoproterenol may aid in identification of patients with congenital long QT syndrome.