bluuebunny/crossref_metadata_2025_split huggingface dataset:
QT Dispersion as a Marker for Response to Quinidine in Patients with Ventricular Tachyarrhythmias
Authors: Kertland Heather , White C. Michael , Chow Moses S.S. , Kluger Jeffrey 
Published: October 2006

Objective:This study was undertaken to measure the effect of quinidine on QT dispersion and to determine whether changes in QT dispersion are associated with the acute response to quinidine in patients with ventricular tachycardia. Methods:In 36 patients with inducible ventricular tachycardia during programmed electrical stimulation (PES), QT and JT intervals were measured in all 12 leads of electrocardiograms recorded at baseline and after quinidine. QT/JT dispersion was calculated by subtracting the smallest from the largest interval; QTc and JTc dispersion were also calculated. Response to therapy was defined as the inability to induce a ventricular tachyarrhythmia during a repeat PES study. Results:Quinidine significantly prolonged the QTc and JTc intervals in the patients who responded to quinidine (n = 12) and in the nonresponders (n = 24). At baseline, QTc dispersion was similar in responders and nonresponders. However, quinidine increased QTc dispersion in nonresponders (from 78 ± 28 to 113 ± 40 ms, P < 0.05) but not in responders (from 81 ± 26 to 83 ± 42 ms). A similar pattern was seen for QT dispersion, JT dispersion, and JTc dispersion. Conclusion:QT dispersion increases in nonresponders, but not in responders to quinidine for ventricular tachycardia. This QT dispersion profile is distinct from the Class III antiarrhythmics and may explain results from large clinical trials and delineate a new safety and efficacy marker.
Dispersion of the QT Interval in Subjects with Frequent Nonsustained Ventricular Arrhythmias and No Underlying Heart Disease: Arrhythmogenic Substrate or Mechanoelectrical Feedback of Arrhythmias?
Authors: Malfatto Gabriella , Ciambellotti Francesca , Chianca Roberto , Bragato Renato , Branzi Giovanna , Leonetti Gastone , Facchini Mario 
Published: October 2006

Background: QT dispersion (QTd) on the ECG is thought to reflect the temporal and spatial inhomogeneity of repolarization in the underlying myocardium. In myocardial infarction, ischemia, and long QT syndromes, an increased QTd is associated with a propensity for malignant ventricular arrhythmias and sudden cardiac death. We investigated this feature of the repolarization process in subjects with frequent ventricular arrhythmias and structurally normal hearts.Methods: Forty‐nine patients referred for frequent, nonsustained ventricular arrhythmias (45 ± 14 years, ×± SD, 61% female) had normal ventricular dimensions and function, no late potentials, and normal ECG. They were compared with 30 controls (42 ± 13 years, 50% female). QTd was measured as the difference between the longest and the shortest QT in the six precordial leads at a paper speed of 50 mm/s.Results: In patients, QTc was similar to that of controls: 395 ± 21 versus 386 ± 20. However, QTd was greater: 49 ± 20 ms versus 32 ± 14 ms, P < 001. Moreover, 18 patients (36%) had QTd exceeding 60 ms—a value superior to the mean normal value of 2 SD—compared to only 1 control (3%) (P < 0.01). Finally, patients with more frequent ventricular arrhythmias had larger QTd.Conclusions: In patients with frequent nonsustained ventricular arrhythmias and otherwise normal hearts, QT interval dispersion is increased. We speculate that, instead of representing a specific electrophysiological substrate of arrhythmias, QT dispersion in this specific population could result from arrhythmias themselves through a possible mechanoelectrical feedback.
Prognostic Significance of Heart Rate Variability During the First 24 Hours of Acute Myocardial Infarction: A 5‐Year Follow‐up Study
Authors: Sánchez Antonio González , García‐Alberola Arcadio , Lázaro Cristina Llamas , Jimenez Pagan Francisco Javier , Bermúdez Eduardo Pinar , Mingorance Guillermo Vignote , Hernandez Juan Martinez , Valdés Mariano 
Published: October 2006

Background: The prognostic value of heart rate variability (HRV) measured within the first 24 hours of acute myocardial infarction was assessed in 94 consecutive patients.Methods: The mean of standard deviation of normal R‐R intervals for all 5‐minute segments (SDNN index), the width of the R‐R interval histogram at 10% and 50% of the peak, and three frequency‐domain measures of HRV (low frequency [LF], high frequency [HF], and LF/HF ratio) were calculated from a continuous ECG recording taken within the first hours of admission and their prognostic value for long‐term events was studied.Results: During the follow‐up period (56.7 ± 5.9 months) 6 sudden and 7 nonsudden cardiac deaths occurred. Time‐domain measurements of HRV were lower in patients with sudden death (SDNN index: 27.0 ± 20.2 vs 47.5 ± 20.7 ms in survivors, P < 0.001). LF and HF power, but not the LF/HF ratio, were also inversely associated with sudden death. No significant differences were found between survivors and patients with nonsudden cardiac death. After adjustment for other clinical covariates, LF and HF power remained significantly associated with sudden death.Conclusion: We conclude that heart rate variability measured within the first 24 hours of myocardial infarction is a strong predictor of sudden death during subsequent follow‐up.
Modulation of Electrical Microvolt Level T‐Wave Alternans and Left Ventricular Late Potentials Evaluated by Heart Rate Variability Indices, QT Dispersion, and Plasma Catecholamine Levels
Authors: Kurita Akira , Matsui Takemi , Ishizuka Toshiaki , Takase Bonpei , Satomura Kimio 
Published: October 2006

Objective: The purpose of this study was to investigate how the modulation of electrical microvolt level T‐wave alternans (Twa) relates to left ventricular late potentials as evaluated by heart rate variability (HRV), QT dispersion, and plasma catecholamine levels.Background: The Twa and left ventricular late potentials are promising noninvasive powerful markers for risk prediction in patients with ischemic heart disease (IHD) and/or cardiomyopathy. However, their relation to autonomic activity is unclear.Methods: In 56 patients with stable IHD‐measured Twa at rest and during controlled bicycle ergometer testing, we simultaneously recorded recent noninvasive electrocardiographic approaches, such as HRV, QT dispersion, and left ventricular late potentials. Plasma norepinephrine (NE) and epinephrine (E) were also measured.Results: (1) There were no significant differences in clinical findings, NE, and E levels between positive (group A) and negative (group B) Twa. Left ventricular late potentials, LF (low frequency spectra), as well as HF (high frequency spectra) in group A were significantly lower than in group B, but LF/HF did not differ significantly between the two groups. There was a significant inverse correlation between Twa microvoltage and LF/HF that was higher during exercise (r = ‐0.51, P = 0.006) than at rest (r = ‐0.34, P < 0.01). (2) There were no significant differences in clinical findings between positive (group C) and negative (group D) left ventricular late potentials. Plasma NE in group C was significantly higher than in group D (1060 ± 429 pg/mL vs 395 ± 219, P < 0.05). Furthermore, LF/HF in group C was significantly lower than in group D (0.96 ± 0.27 vs 1.1 ± 0.11, P < 0.05). There were no significant correlations between left ventricular late potential parameters and QT or QTc dispersion.Conclusions: The Twa microvoltage in patients with stable IHD exhibits similar physiologic conditions as in patients with lower HRV indices. The presence of left ventricular late potentials might be affected by sympathetic nerve modulation.
Bias of QT Dispersion
Authors: Lund Kaspar , Arildsen Hanne , Perkiömäki Juha S. , Huikuri Heikki V. , May Ole , Pedersen Anders Kirstein 
Published: October 2006

Background: Prolonged QT dispersion (QID) is associated with an increased risk of arrhythmic death but its accuracy varies substantially between otherwise similar studies. This study describes a new type of bias that can explain some of these differences.Material: One dataset (DiaSet) consisted of 356 subjects: 169 with diabetes, 187 nondiabetic control persons. Another dataset (ArrSet) consisted of 110 subjects with remote myocardial infarction: 55 with no history of arrhythmia and 55 with a recent history of ventricular tachycardia or fibrillation.Methods: 12‐lead surface ECGs were recorded with an amplification of 10 mm/mV at a paper speed of 50 mm/s. The QT interval was measured manually by the tangent‐method. The bias depends on the magnitude of the measurement errors and the measurable part of the bias increases with the number of the repeated measurements of QT.Results: The measurable bias was significant for both datasets and decreased for increasing QTD in the DiaSet (P < 0.001) and in the ArrSet (P = 0.11). The bias was 2.5 ms and 1.9 ms at QTD = 38 ms and 68 ms, respectively, in the ArrSet, and 7.5 ms and 2.8 ms at QTD = 19 ms and 55 ms, respectively, in the DiaSet.Conclusions: This study shows that random measurement errors of QT introduces a type of bias in QTD that decreases as the dispersion increases, thus reducing the separation between patients with low versus high dispersion. The bias can also explain some of the differences in the mean QTD between studies of healthy populations. Averaging QT over three successive beats reduces the bias efficiently. A.N.E. 2001;6(1):38–42
Effects of Glucose‐Insulin‐Potassium Infusion on QT Dispersion in Patients with Acute Myocardial Infarction
Authors: Wolk Robert , Lusawa Tomasz , Ceremuzynski Leszek 
Published: October 2006

Background: Increased QT dispersion during acute myocardial infarction (AMI) has been associated with the occurrence of ventricular arrhythmias. Also, serum potassium levels have been shown to be relevant to the arrhythmic risk in this group of patients. The aim of the present study was to assess changes in QT dispersion during infusion of glucose‐insulin‐potassium (GIK) during AMI.Methods: Patients from the Pol‐GIK study were analyzed retrospectively. The patients were selected from the placebo (1000 ml of 0.89% NaCI) and the GIK (1000 ml of 10% dextrose, 20–32 units of insulin, 80 mEq K+) groups (18 and 24 patients, respectively). QT interval duration and dispersion the difference between the longest and shortest QT intervals) were measured at baseline, 18–24 hours into placebo/GIK infusion and 24 hours after the end of infusion.Results: In the placebo group, plasma potassium levels changed from 4.1 ± 0.5 mmol/L at baseline to 4.6 ± 0.8 mmol/L during infusion (P < 0.05) and 4.6 ± 0.4 mmol/L after infusion, whereas in the GIK group the respective values were 4.0 ± 0.4, 4.6 ± 0.3 (P < 0.0001), and 4.5 ± 0.5 mmol/L. QT interval duration was stable throughout the study and there was no difference between the groups. The two groups did not differ in respect to QT dispersion at any time point, the respective values were 79 ± 28, 65 ± 25, and 77 ± 27 ms in the placebo group, and 61 ± 35, 60 ± 26, and 76 ± 43 ms in the GIK group. The incidence of arrhythmias was also similar in both groups.Conclusions: GIK, at the dose used, is unlikely to affect heterogeneity of ventricular repolarization during AMI. A.N.E. 2001;6(1)50–54
Modulation of Ventricular Repolarization and R‐R Interval Is Altered in Patients with Globally Impaired Cardiac 123I‐MIBG Uptake
Authors: Yoshida Naohiro , Nozawa Takashi , Igawa Akihiko , Fujii Nozomu , Kato Bun‐ichi , Mizumaki Koichi , Fujiki Akira , Asanoi Hidetsugu , Seto Hikaru , Inoue Hiroshi 
Published: October 2006

Background: Cardiac 123l‐metaiodobenzylguanidine (MIBG) imaging is widely used to assess cardiac sympathetic neuronal function. However, physiologic significance of impaired cardiac MIBG uptake is not fully elucidated. The purpose of the present study was to determine influences of abnormal cardiac sympathetic neuronal function on heart rate variability (HRV) and ventricular repolarization process.Methods: Twenty‐nine patients with prior myocardial infarction were divided into two groups by a heart‐to‐mediastinum ratio (H/M) of MIBG scintigraphy. Ten patients with globally decreased MIBG uptake (group I: H/M < 1.5), 19 patients with partially decreased MIBG uptake (group II: H/M < 1.5), and 17 control subjects with normal MIBG uptake (group III) were studied. Holler recording and a standard 12‐lead electrocardiography were used for evaluation of HRV, QT‐RR relation, and QT dispersion.Results. Low, high, and total frequency components decreased in groups I and II, as compared to that of group III. The reduction of these frequency domain measures was more severe in group I than in group II, but the differences did not reach statistical significance. Circadian variation of frequency domain measures disappeared in group I. The slope of QT‐RR relation was significantly greater in group I than in groups II and III. QT dispersion was also greater in group I (64 ± 25 msec) than in group 11(43 ± 19 msec) and group III (28 ± 9 msec).Conclusion. These results suggest that patients with sympathetic neuronal dysfunction inferred from globally impaired cardiac MIBG uptake have an altered modulation of ventricular repolarization process as well as decreased HRV.
Perception and Documentation of Arrhythmias after Successful Radiofrequency Catheter Ablation of Accessory Pathways
Authors: Oddsson Hjörtur , Walfridsson Håkan , Edvardsson†† Nils 
Published: October 2006

Background: Some patients continue to have palpitations in spite of successful ablation of Wolff‐Parkinson‐White (WPW) syndrome. Recurrence of accessory pathways as well as unrelated arrhythmias may explain the symptoms.Methods: We followed 194 consecutive patients after successful radiofrequency catheter ablation of overt (147) or concealed (47) WPW syndrome. The mean duration of symptoms was 16 ±; 13 years. Atrial fibrillation was documented in 54 patients (24%) prior to ablation. 185 patients responded to a questionnaire 24 ±; 12 months after ablation.Results: The physical well‐being was improved in 94%, unchanged in 5%, and deteriorated in 1%. However, 76 patients (39%) reported arrhythmia symptoms, in 40 patients causing pharmacological treatment (14 patients) and/or continued contact with their doctor. The underlying arrhythmias were orthodromic tachycardia (10), atrial fibrillation (12), premature beats (12), atrial flutter (1), and ventricular tachycardia (1), while in four patients no explanation was found. Minor symptoms in the other 36 patients were explained by premature beats in 29, while unexplained in 7. All patients with atrial fibrillation after ablation had atrial fibrillation before ablation. Ten relapses of WPW syndrome occurred: eight were known before the time of the questionnaire, two were confirmed at transesophageal atrial stimulation.Conclusion: 94% patients with a long history of tachyarrhythmias due to the WPW syndrome reported improved physical well‐being after ablation, but palpitations were common during a 2‐year follow‐up period; 8% continued to use pharmacological antiarrhythmic treatment. Five percent had symptomatic relapses and in 6% atrial fibrillation episodes reoccurred, i.e., in half of those who had atrial fibrillation before ablation. A.N.E. 2001; 6(3):216–221
THE ORDER OF VENTRICULAR EXCITATION IN HUMAN BUNDLE‐BRANCH BLOCK*†
Authors: Wilson Frank N. , Macleod A. Garrard , Barker Paul S. 
Published: October 2006

IN previous articles from this laboratory1,2 it has been pointed out that, in accordance with the laws which govern the flow of electric currents in volume conductors, the potential variations produced by the cardiac muscle are very much greater in magnitude in the immediate neighborhood of the heart than at a distance from it. It has been shown that when one electrode of the string galvanometer is placed upon the pre‐cordium, the position of the second electrode, so long as it is distant from the heart, has comparatively little influence upon the form of the ventricular electrocardiogram. Attention has been called to certain resemblances between leads of this type and direct leads of the kind employed by Lewis and Rothschild3 in which one electrode is placed in actual contact with the ventricular muscle and the other upon the chest wall. In both cases the form of the ventricular complex is determined in a very large measure, although not to quite the same extent in the former as in the latter, by the potential variations of the exploring electrode; in both cases the muscle units which lie nearest this electrode exert individually a much greater effect upon its potential than those which are more distant from it.Curves obtained by leading from points on or near the heart to one of the extremities utilized in taking the three standard indirect leads may be freed from the influence exerted by potential variations of the indifferent electrode by a method which we have recently described.4 When this electrode is placed upon the left leg the correction is made by subtracting from each ordinate of the recorded curve one‐third of the sum of the deflections, measured in. millivolts, inscribed in Leads II and III at the corresponding instant in the cardiac cycle. It is possible in this way to determine, at least approximately, the time course of the potential of the exploring electrode, and thus to eliminate any difference beween direct and semidirect leads for which potential variations of the indifferent electrode are responsible.
Effects of Hormone Replacement Therapy on Heart Rate Variability in Postmenopausal Women
Authors: Yildirir Aylin , Kabakci Giray , Yarali Hakan , Aybar Funds , Akgul Ebru , Bukulmez Orhan , Tokgozoglu Lale , Gurgan Timur , Oto Ali 
Published: October 2006

Background: Hormone replacement therapy (HRT) is associated with reduced cardiovascular risk, but the underlying mechanism(s) are not fully understood. This study investigated the effects of a 6‐month course of HRT on cardiac autonomic function parameters assessed by heart rate variability (HRV) in postmenopausal women.Methods: Forty‐six healthy postmenopausal women (age 48 ± 5, range 40–60) with normal baseline electrocardiogram and negative exercise testing were enrolled. HRT, which was either 0.625 mg/day conjugated equine estrogen (CEE) plus 2.5 mg/day medroxyprogesterone acetate or 0.625 mg/day CEE alone were administered depending on hysterectomy status. Power spectral analysis of HRV was performed to calculate the low frequency component in absolute (LF) and normalized units (LF nu), high frequency component in absolute (HF), and normalized units (HF nu), and the LF/HF ratio. The standard deviation of RR intervals (SDNN) was calculated from the time series of RR intervals.Results: A 6‐month course of HRT did not significantly alter resting heart rate (P > 0.05). The LF/HF ratio and LF nu significantly decreased after HRT (P = 0.022 and P = 0.032), whereas a significant increase was noted in the HF component of HRV (P = 0.043), indicating an improvement in cardiac autonomic function. The SDNN value, which was 28.8 ± 11.8 ms before HRT significantly increased to 35.4 ± 16.7 ms after 6 months (P = 0.011).Conclusion: Our results indicate that a 6‐month course of HRT may significantly improve cardiac autonomic function parameters, a finding that could at least partly explain the potential cardiopro‐tective effect(s) of HRT. A.N.E. 2001;6(4):280–284
Age, Gender, and Autonomic Tone Effects on Surface Electrocardiographic Indices of Ventricular Repolarization
Authors: Taneja Taresh , Larsen Jennifer , Goldberger Jeffrey , Kadish Alan 
Published: October 2006

Background: Prolonged QT offset dispersion (QToD), an index of heterogeneity of ventricular repolarization, is thought to be an independent predictor of all‐cause and cardiovascular mortality. However the influence of gender and autonomic tone in healthy adults on age‐related changes in measures of ventricular repolarization are not well characterized.Methods: QToD and T wave complexity were measured in 56 healthy subjects with no detectable heart disease (by echo and stress test)—38 young subjects with a mean age of 28 ± 4 years and 18 old subjects with a mean age of 71 ± 7 years. QToD and T wave complexity were computed from 12‐lead ECGs using the GE Marquette QT Guard automated analysis program with manual over‐reading at rest (baseline), following exercise, and double autonomic blockade with atropine and propranolol. Data was analyzed using factorial ANOVA.Results: Young males had a significantly greater QToD than young and old females at baseline (28 ± 5 ms, 23 ± 5 ms, and 22 ± 5 ms, respectively, P < 0.01), an intrinsic effect independent of changes in autonomic tone. In contrast, females had significantly greater T wave complexity than males following exercise and double autonomic blockade with a definite trend at baseline. There was no correlation between T wave complexity and QToD.Conclusions: Age and gender demonstrate a complex interaction on indices of myocardial repolarization with different measures behaving differently. These findings have implications for better understanding age and gender effects on myocardial electrophysiology. A.N.E. 2001;6(4):290–297
Heart Rate Variability in Patients with Congenital Long QT Syndrome
Authors: Perkiömäki Juha S. , Zareba Wojciech , Couderc Jean‐Philippe , Moss Arthur J. 
Published: October 2006

Background: The congenital long QT syndrome (LQTS) affecting myocardial repolarization is caused by mutations in different cardiac potassium or sodium channel genes. Adrenergic triggers are known to initiate life‐threatening torsade de pointes ventricular tachycardias in LQTS patients, and anti‐adrenergic therapy has been shown to be effective in many cases. Despite this well‐documented adrenergic component, the data about autonomic modulation of the heart rate in LQTS, as described by heart rate variability (HRV) analysis, are very limited.Methods: Conventional time‐ and frequency‐domain and newer nonlinear measures of HRV were compared in resting conditions among 27 LQTS patients with gene mutations at the LQT1 (n = 8), LQT2 (n = 10) or LQT3 (n = 9) loci and 34 LQTS noncarrier family members.Results: None of the conventional time‐ or frequency‐domain or newer nonlinear measures of HRV differed significantly between the LQTS carriers and LQTS noncarriers or between the LQT1, LQT2, and LQT3 carriers.Conclusions: These findings suggest that baseline cardiac autonomic modulation of the heart rate measured in resting conditions by traditional or newer nonlinear measures of HRV is not altered in LQTS patients. Furthermore, no differences are observed in HRV parameters between LQTS patients with potassium (KvLQT1, HERG), and sodium (SCN5A) ion channel gene mutations. HRV analysis in resting conditions does not improve phenotypic characterization of LQTS patients. A.N.E. 2001;6(4):298–304