bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slowed Conduction with Antiarrhythmic Drugs Reduces High Frequency Energy of the Signal‐Averaged Electrocardiogram
Authors: Bloomfield Daniel M. , Freedman Roger A. , Steinberg Jonathan S. 
Published: October 2006

Background: We have previously demonstrated that high frequency QRS energy decreases after experimental myocardial infarction (Ml) and is lower in patients who have had MI compared to controls. The mechanism for this decrease in high frequency QRS energy is unclear. The objective of this study was to evaluate the effect of slowed myocardial conduction on high frequency QRS energy measured on the signal‐averaged SAECG. We hypothesized that slowed conduction in the infarcted ventricle may be responsible for the decrease in high frequency QRS energy. In order to test this hypothesis, we examined antiarrhythmic drug therapy known to slow conduction (propafenone) compared to drug therapy with minimal effects on conduction (sotalol).Methods: In patients with sustained ventricular tachyarrhythmias undergoing serial drug testing, SAECGs were obtained before and after antiarrhythmic therapy. After filtering the leads with a spectral band‐pass (15–40 Hz, 40–80 Hz, and 80–300 Hz) filter, the vector magnitude was con structed, and the energy (in μV sec) was calculated for the entire QRS by integrating the area under the filtered QRS complex.Results: Propafenone significantly prolonged QRS duration (+17%, P > 0.001) and significantly reduced QRS energy (‐16.1% to 21.8%, P > 0.0001) in all three band widths. Sotalol did not have either effect (P = ns). There was a strong correlation between the prolongation of the filtered QRS and the drop in QRS energy for all three band widths (r values ranging from 0.64–0.90, all P > 0.05). When the changes in QRS energy were corrected for QRS duration, the results did not change.Conclusion: The Class IC antiarrhythmic drug propafenone, known to decrease myocardial conduction velocity, significantly reduced QRS energy in all three band widths, whereas the Class III drug sotalol did not. These data are consistent with the hypothesis that decreases in low and high frequency QRS energy after Ml result in part from slowed conduction.
Spectral Analysis of RR and R‐T Variabilities in Patients with Coronary Artery Disease
Authors: Sandrone G. , Torzillo D. , Fundarò C. , Porta A. , Danna P. , Polese A. , Malliani A. , Lombardi F. 
Published: October 2006

Background: As the duration of the Q‐T interval is dependent upon the length of the preceding cardiac cycle, changes in QT interval duration mainly reflect, in normal subjects, the physiological beat‐by‐beat variability of the sinus node. However, little information is available on short‐term Q‐T variability in patients with an abnormal neural modulation of the sinus node.Methods: We analyzed, with autoregressive techniques, RR and R‐Tapex, and R‐Tend variabilities in 12 patients after myocardial infarction, in 13 patients before and after percutaneous transluminal coronary angioplasty (PTCA), and in 10 age‐matched controls.Results: No significant differences in mean value and variance of RR, R‐Tapex, and R‐Tend interval among the three groups of subjects were observed. Spectral analysis of RR variability was characterized by signs of sympathetic activation with a predominance of low frequency (LF) component in patients after myocardial infarction (69 ± 5 nu) and before PICA (74 ± 5 nu) in comparison to controls (50 ± 4 nu). Instead, spectral energy was equally distributed within LF and HF (high frequency) components of RTapex and R‐Tend variabilities in the three groups of subjects.Conclusions: These data indicate that the predominance of LFRR in normalized units, indicating an increase of sympathetic modulation of sinus node activity in patients with coronary artery disease, are not accompanied by a parallel predominance of the LF component of R‐Tapex and R‐Tend variabilities. This difference reflects, in our opinion, a minor dependency of duration of ventricular repolarization from the preceding cardiac cycle in patients with coronary artery disease.
Absence of Increased Systemic Vascular Resistance During Syncopal Episodes in Patients with Tilt‐Positive Neurocardiogenic Syncope
Authors: Perl Shira , Weitzman Shimon , Battler Alexander , Katz Amos 
Published: October 2006

BackgroundThe purpose of this study was to elucidate the mechanism of syncope in patients with neurocardiogenic syncope (NCS) by measuring hemodynamic parameters continuously during a head‐up tilt (HUT) test.MethodsTwenty‐three adults (mean age 22.6 ± 9.8, range 15–62) participated in the study: 16 with a history of syncope suggesting NCS and 7 healthy volunteers who served as controls. The subjects underwent a 45‐minute 60° tilt test. Heart rate and blood pressure were monitored continuously. The stroke volume was measured every minute by noninvasive impedance cardiography, and systemic vascular resistance was calculated from these measurements. The test was terminated when syncope occurred or after 45 minutes in an upward position.ResultsEight of the 16 patients had a positive HUT, while all control subjects had a negative HUT. Decreased stroke volume and cardiac index were observed in all subjects and subgroups in the upward position, compared to the rest position (P < 0.01). Systemic vascular resistance rose in patients with a negative HUT and all controls (P < 0.03), but did not change in the HUT‐positive patients (P = 0.25), during the HUT. Systemic vascular resistance was significantly lower in the upward position in the positive HUT than in the other groups (P < 0.04), but there were no differences in the cardiac index.ConclusionsFailure to achieve an appropriate increase in systemic vascular resistance may be an important mechanism in some cases of NCS and should be taken in account when considering therapeutic options. Impedance cardiography is a noninvasive technique for the detection of this abnormal response and can be used to assess the effect of drug therapy on systemic vascular resistance. A.N.E. 1999; 4(2):121–129
Continuously Recorded Physical Activity Level During Myocardial Ischemia Detected by Ambulatory Electrocardiography
Authors: Podolec P. , Jasek S. , Droste C. , Kardos A. , Tracz W. , Roskammt H. 
Published: October 2006

BackgroundThe goal of the study was to establish the usefulness of a new device, the Actograph, to differentiate the causes of ischemia detected in ambulatory Holter monitoring. Twenty‐five patients (7 women, 18 men) with angiographically proven coronary artery disease and stable effort angina were evaluated.MethodsPatients had their physical motor activity (PMA) registered by means of an Actograph simultaneously with Holter monitoring during 24 hours when they underwent a standardized bicycle exercise test and performed their usual daily activity with mandatory walking and stair climbing.ResultsNineteen of 25 patients had 97 transient ischemic episodes (TIEs) in the postexercise monitoring period (5.1 episodes/patient and 91.5 min/patient). Seventy‐four TIEs were associated with a high heart rate (HR) increase and evidence of PMA. Seven TIEs occurred without HR increase, but with evidence of considerable physical exercise. During 13 TIEs there was HR increase without any proof of physical activity. In only three TIEs there was neither HR increase nor measurable PMA. Patients’activity period during 24 hours extended from 19.6%–48.9% of recording time. The higher the patients’activity level during the 24‐hour period, the higher the number of TIEs were noted (r = 0.57, P < 0.03). Increased activity was recorded in patients’diaries only during 51(69%) of TIE with evidence of increased HR and PMA. Patients who had only asymptomatic TIEs on the ambulatory ECG had significantly higher PMA than patients without ischemia during Holter monitoring (26% vs 33%; P < 0.001). PMA during walking was significantly higher than during bicycle exercise and climbing stairs (P < 0.001). Surprisingly, the physical activity episodes with lowest PMA, bicycle exercise testing, in all cases were accompanied by TIE, while activity episodes with highest PMA, walking, provoked TIEs only in 40% of cases. There is clearly no correlation between activity measured by the Actograph and HR increase during cycloergometer tests (R2 = 0.08), while stair climbing and walking shows good correlation (R2 = 0.6).ConclusionsThe Actograph is a useful device that gives additional insight into the pathophysiology of ischemia. The weakness of the method is lack of the ability to measure intensity of physical activity.
Heart Rate Variability Is Decreasing During Paroxysmal Atrial Fibrillation
Authors: Piot Olivier , Halimi Franck , Jouven Xavier , Lavergne Thomas , Guize Louis , Le Heuzey Jean‐Yves 
Published: October 2006

BackgroundThe high R‐R variability in permanent atrial fibrillation (AF) is stable. Its behavior in paroxysmal AF is unknown. The aim of this study was to examine heart rate variability behavior during paroxysmal AF and its relationship with clinical characteristics by using time‐domain indices and scatterplot analysis.MethodsIn 43 patients, R‐R variability was assessed by time‐domain indices and graphical measurements of scattering area (SA) on scatterplot for each sample of 150‐second ventricular rhythms extracted at the onset, the middle, and before termination of AF episodes recorded on Holter monitoring. Results were compared between the three time periods, and a nested procedure assessed the components of the SA variance.ResultsIn 110 episodes lasting 89 ± 130 minutes with a mean of 2.5 ± 3 (1–12) per patient, mean R‐R interval did not significantly change while time‐domain indices and SA significantly decreased between the three time periods (P < 0.05 for SD and CV, P < 10−2 for rMSSD and pNN50, P < 10−4 for SA, ANOVA 1). The magnitude of the decrease in SA was not related to any episode characteristic; in addition, there was no variation from episode to episode within patient (1% of SA variance), and the high variation between patients (70%, P < 10−4) was not related to any clinical parameter.ConclusionsHeart rate variability decreases gradually during paroxysmal AF. This decrease is peculiar to each patient, unrelated to clinical status. A.N.E. 1999; 4(2):144–151
Relationship Between Autonomic Control of Heart Rate and QT Dispersion in Patients with Acute Anterior Wall Myocardial Infarction
Authors: Mazur Alexander , Strasberg Boris , Kusniec Jairo , Imbar Shula , Sulkes Jacqueline , Abramson Evgeny , Sclarovsky Samuel 
Published: October 2006

BackgroundHeart rate variability (HRV) and QT dispersion are new and promising noninvasive indices for postinfarction risk stratification. The relationship between measures in patients with acute myocardial infarction (AMI) is unknown.MethodsWe analyzed short‐term HRV and standard electrocardiogram recordings for QT dispersion in 56 patients with first Q‐wave anterior wall AMI.ResultsAll frequency domain measures of HRV correlated inversely with the magnitude of QT dispersion. The correlations were relatively stronger for rate‐corrected (−0.46 to −0.59) than for original values (−0.37 to −0.5) of QT dispersion. Similarly, the average normal cardiac cycle length (average NN) computed from HRV recordings correlated weakly and inversely with the magnitude of noncorrected QT dispersion (r =−0.29).ConclusionsThe inverse relationships between QT dispersion and both NN interval and HRV found in the present study suggest impaired adaptation of ventricular repolarization to changes in heart rate in AMI patients. Abnormal autonomic modulation of ventricular repolarization may thus result in increased QT dispersion. This finding may provide some insight into the mechanism underlying increased risk of sudden death after AMI. A.N.E. 1999; 4(2):152–157
Alteration in QT‐RR Relationship in Diabetic Patients with Autonomic Dysfunction
Authors: Shimono Mayumi , Fujiki Akira , Asahi Toshimi , Inoue Hiroshi 
Published: October 2006

BackgroundImpaired autonomic nervous activity and changes in ventricular repolarization might be related to catastrophic events in diabetic patients.MethodsWe analyzed the QT‐RR relationship and autonomic activity with Holter monitoring in 20 diabetic patients and 10 controls. The diabetic group was divided into two groups: 9 patients with normal coefficient of variance of RR interval (CVRR > 2.5%, DMN group) and 11 with low CVRR (CVRR≤; 2.5%, DML group). Mean hourly QT and RR intervals were determined using the first 10 sinus beats of every hour. Spectral power of heart rate variability was determined with the fast Fourier transform technique.ResultsThe DML group had shorter RR and QT intervals during sleep compared with the DMN group and control group. There was no difference in corrected QT interval among the three groups. The DML group showed decreased circadian variation of high‐frequency (HF) power, and steeper regression line and smaller correlation coefficient of QT‐RR relationship compared with other groups. There was an inverse correlation between InHF and the slope of the regression line of the QT‐RR relationship.ConclusionsThese results indicate that modulation of QT interval with heart rate is impaired along with impairment of cardiac parasympathetic activity in the DML group. Altered modulation of ventricular repolarization might contribute to the pathogenesis of catastrophic cardiac events in diabetic patients with neuropathy.
Prediction of Cardiac Death in Patients with Bundle Branch Block After Myocardial Infarction
Authors: Sierra Gilberto , Morel Patrick , Jean‐Lucien Rouleau  , Ferguson John , Davies Richard F. , Stewart Duncan J. , Talajic Mario , Gardner Martin , Dupuis Robert , Lauzon Claude , Sussex Bruce , Warnica Wayne , Le Guyader Pierre , Nadeau Reginald , Savard Pierre 
Published: October 2006

BackgroundLeft (LBBB) and right (RBBB) bundle branch block (BBB) patients have an increased incidence of cardiac death after myocardial infarction (Ml). The purpose of this study was to assess the value of the signal‐averaged electrocardiogram (SAECG) and other clinical variables for the prediction of cardiac death after MI in BBB patients.MethodsSAECGs were recorded 5–15 days after MI in 76 LBBB and 79 RBBB patients. The SAECG was analyzed in the time domain and the frequency domain (wavelet analysis in 7 frequency bands ranging from 0.05 to 250 Hz).ResultsDuring follow‐up (17 ± 8 months), cardiac death occurred in 22 LBBB (28.9%) and 12 RBBB patients (15.2%). None of the SAECG time‐domain variables were significantly different between patients with and without cardiac death. In LBBB patients, univariate analysis showed that one wavelet parameter in the 3.9‐ to 7.8‐ Hz frequency band (P = 0.008), inhospital recurrent Ml (P = 0.002), left ventricular ejection fraction (LVEF) < 30% (P = 0.004), lack of percutaneous transluminal coronary angioplasty (P = 0.02), and history of angina (P = 0.029) were significantly different in cardiac death patients. In RBBB patients, only recurrent angina was significantly different (P = 0.025). In LBBB patients, the combination of recurrent Ml or LVEF < 30% displayed the best predictive values: sensitivity (85.7%), specificity (76.6%), positive (52.2%), negative (94.7%), and total (78.7%) predictive accuracies and risk ratio of 9.9. The effect of recurrent Ml and LVEF < 30% remained after statistical adjustment by means of regression using Cox proportional hazards.ConclusionsHigh‐risk Ml patients can be identified by recurrent Ml and LVEF < 30% in LBBB patients, and by recurrent angina in RBBB patients. SAECG did not demonstrate incremental information for the purpose of risk stratification in BBB patients.
Influence of Cigarette Smoking on Heart Rate Variability in Young Healthy Subjects
Authors: Andrikopoulos George K. , Dilaveris Polychronis E. , Richter Dimitris J. , Gialafos Elias J. , Lazaki Elena A. , Avgeropoulou Catherine K. , Gialafos John E. 
Published: October 2006

BackgroundCigarette smoking is strongly related to decreased vagal cardiac activity and increased cardiac death. We sought to examine the short‐term effects of smoking on heart rate variability (HRV) in healthy young subjects in the sitting position to investigate the influence of smoking on autonomic cardiac control.MethodsThirty‐two healthy volunteers (18 males, 14 females, 21 habitual smokers and 11 nonsmokers, mean age 30 ± 3 years, range 24–36 years) were studied. Smokers were asked not to smoke for 8 hours prior to examination. Mean, SDNN, rMSSD, pNN50, total power, LF, HF, and LF/HF ratio were measured for 30 minutes, divided into six periods of 5 minutes each. Smoking of a single cigarette took place during the second period.ResultsSmoking caused a significant increase of the LF/HF ratio and of the normalized values of the LF component. A significant decrease in absolute values of total power, LF, and HF components was noticed. All time‐domain indices were significantly decreased. We also noticed that although the changes appeared during smoking (second period) the maximal changes were documented 5 to 10 minutes after smoking cessation (third and fourth periods).ConclusionsCigarette smoking in the sitting position causes a transient decrease in vagal cardiac control and a moderate sympathetic activation. These changes last for at least 30 minutes and are compatible with a modulation of the autonomic control of the sinoatrial node toward sympathetic predominance. Despite the differences concerning the baseline HRV measures between nonsmokers and habitual smokers, an almost identical pattern of sympathovagal modulation was observed.
A Comparison of T‐Wave Alternans and QT Dispersion as Noninvasive Predictors of Ventricular Arrhythmias
Authors: Berul Charles I. , Michaud Gregory F. , Lee Victor C. , Hill Sharon Laneau , Estes Mark , Wang Paul J. 
Published: October 2006

Background:The purpose of this study was to compare the utility of T‐wave alternans and dispersion markers for predicting vulnerability to ventricular arrhythmias. Microvolt level T‐wave alternans, QT dispersion (QTd), JT dispersion, and other dispersion indices have been postulated as noninvasive markers of vulnerability to ventricular arrhythmias. However, T‐wave alternans has not been directly compared to dispersion markers in the same patient population. Methods:Twenty‐four patients underwent electrophysiological study to investigate recent syncope, ventricular tachycardia, or ventricular fibrillation. Digitized orthogonal ECGs were obtained to investigate the presence of T‐wave alternans using spectral analysis, and standard 12‐lead ECGs were obtained for QT and JT dispersion analysis. Results:T‐wave alternans measurements showed greater sensitivity than QT or JT dispersion, but similar results as the variation coefficient of the JT interval. There was no statistically significant difference in specificity, predictive values, or clinical accuracy between T‐wave alternans and any of the dispersion markers (P = N.S.). The combination of increased QT or JT dispersion and T‐wave alternans was the most specific predictor. Conclusions:Heterogeneity of repolarization amplitude and duration may both be important noninvasive ECG markers of ventricular vulnerability. In this small group of high‐risk patients, T‐wave alternans has similar clinical accuracy as the ECG interlead repolarization dispersion markers. The predictive ability of these markers may improve with standardization of methodology or a combination of these approaches. A.N.E. 1999;4(3):274–280
QT Dispersion in Healthy Chinese Children and Adolescents
Authors: Zhang Niu , Ho Ting Fei , Yip William C.L. 
Published: October 2006

Background:QT dispersion (QTd) reflects the interlead difference in QT interval. It may provide a measure of repolarization inhomogeneity. Studies on QTd mainly involve adults, while QTd in children are less well studied. The aim of this study was to evaluate QTd in healthy children and assess the relationship of gender, age, and anthropometric parameters, viz. weight (W), height (H), body mass index (BMI), and body surface area (BSA) to QTd. Methods:Five hundred and one Chinese children and adolescents (243 boys, 258 girls) with no history of cardiovascular diseases were studied. Their ages ranged from 6.3 to 17.5 years. Surface 12‐lead electrocardiograms were measured in each child at rest. QT and R‐R intervals in each of the 12 leads were manually measured at a magnification of 2X. QT was corrected to QTc according to Bazett's formula. QTd was calculated as the difference between the maximum and minimum QT of the measured leads, while corrected QTd (QTcd) was the difference between the maximum and minimum QTc of the measured leads. Adjusted QTd was QTcd divided by the square root of the number of measurable leads. Results:Mean QTd of all subjects was 34 ms (95% Cl 33.6–35.1 msl. Mean QTd for boys and girls was 35 ms and 34 ms, respectively (P = 0.18). Mean QTcd for the whole group was 47 ms (95% Ci 45.8–48.2 ms), while mean adjusted QTcd was 14 ms (95% Cl 13.8–14.5 ms). There were no significant gender differences in QTcd or adjusted QTcd. Weak negative correlation existed between age and QTd, QTd and adjusted QTcd (r =−0.22, r =−0.26, r =−0.21, respectively, P < 0.001 Similarly, QTcd also had a weak significant negative correlation with W (r =−0.20), H (r =−0.21) and BSA (r =−0.22), P < 0.001. However, multiple stepwise regression analysis revealed that only age was significantly related to QTcd (R2 = 0.066) and QTd (R2 = 0.059), P < 0.001. Conclusions:The results of this study indicate a trend of decreasing QTd and QTcd with increasing age, supported by multiple regression analysis. However indices of QTd in children are not influenced by anthropometry. This information may be useful for the clinical application of QTd in children. A.N.E. 1999;4(3):281–285
Signal‐Averaged ECG in Noninvasive Assessment of Reperfusion in the Acute Phase of Myocardial Infarction
Authors: Kulakowski Piotr , Karpiński Grzegorz , Szymot Joanna , Ceremuzyñki Leszek 
Published: October 2006

Background:Coronary artery patency after thrombolytic therapy has important prognostic implications for survival after acute myocardial infarction (Ml). Several noninvasive methods have been tested to assess the effectiveness of thrombolytic therapy. However, the value late potential (LP) analysis from the signal‐averaged ECG for assessment of reperfusion has not been established. Methods:In 50 patients (34 males, 16 females, mean age 59 ± 12 years, range, 35 years to 84 years) with acute Ml, signal‐averaged ECG recordings were performed using the FD‐3 solid‐state Holter recorder and analyzed prior to and 1, 2, and 3 hours from the initiation of thrombolytic treatment. Reduction in ST elevation of > 50% compared with baseline values was taken as a marker of successful reperfusion. Results:At 2 hours, 28 (56 %) patients were considered to have successful reperfusion: LPS were not present in any patient with successful reperfusion compared with 8 (36%) patients without reperfusion (P = 0.002). At 3 hours 31 (62 %) patients were considered to have successful reperfusion: 1 (3%) had abnormal signal‐averaged ECG versus 6 (35%) patients without reperfusion (P = 0.01). An abnormal signal‐averaged ECG identified patients with failed reperfusion with very high specificity and positive predictive value (100% and 100% at 2 hours; 97% and 86% at 3 hours, respectively). Conclusions:Patients with failed reperfusion have abnormal signal‐averaged ECGs more frequently than patients with successful reperfusion. Thus, signal‐averaged ECG may be helpful for identification of patients without reperfusion who may urgently need invasive treatment or rethrombolysis to restore blood flow in the infarct‐related artery. A.N.E. 1999;4(3):301–308