bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characteristics of the Circadian Rhythm of Heart Rate Variability in Patients with Sudden Cardiac Death after Myocardial Infarction
Authors: Itou Tetsushi , Obata Shinichirou , Tateishi Osamu 
Published: October 2006

Background: Sudden cardiac death (SCD) after myocardial infarction, most commonly caused by ventricular fibrillation, is closely associated with autonomic nervous tone. However, the mechanism of SCD and its association with autonomic nervous tone and the circadian rhythm of this tone remain obscure. We examined the characteristics of autonomic nervous tone in patients with SCD using heart rate variability (HRV) analysis.Methods: HRV was analyzed by spectral and nonspectral methods in 46 postinfarction patients, including 6 patients who experienced SCD (SCD[+]) and 40 survivors (SCD[—]). The circadian rhythm of HRV was assessed by a nonlinear least squares method combined with the maximum entropy method (MEM) using data from 24‐hour ambulatory ECGs. The mean follow‐up period was 27 ± 12 months.Results: Midline estimating statistic of rhythm and the amplitude of the high frequency (HF) component in the SCD(+) group were lower than those in the SCD(—) group, and differences of the circadian rhythm of the HF component between the SCD(+) group and the SCD(—) group were observed.Conclusions: A decreased HF component indicating diminished parasympathetic nervous activity was the strongest independent predictor of SCD. These results suggest that postinfarction patients whose parasympathetic nervous activity is low and whose circadian changes are small may be susceptible to SCD.
Early Electrocardiographic Signs of Drug‐Induced Torsades de Pointes
Authors: Svernhage Elisabeth , Houltz Birgitta , Blomström Per , Brachmann Johannes , Crijns Harry , Jensen Steen , Vallin Hans , Swedberg Karl , Edvardsson Nils 
Published: October 2006

Background: The aim of the present analysis was to identify early changes in the surface ECG predicting development of torsades de pointes (TdP) during treatment with almokalant, a Class III antiarrhythmic compound.Methods and Results: In two studies with identical protocols, five patients were reported to have developed TdP. The proarrhythmia occurred 43–137 minutes after start of infusion of almokalant, a selective IKr‐blocking substance. Precordial ECG leads V1–V6 were continuously recorded on tape and analyzed for ECG changes during the first 40 minutes of infusion. The tape recording for one patient was, however, technically insufficient for analysis. Each of the remaining four patients was compared with two control patients from the same study and matched for gender, age, conversion to sinus rhythm, and plasma drug concentration. Prolongation of the QTtop interval, i.e., from the beginning of the Q wave to the first identifiable top of the TU complex, was significantly greater during the 40‐minute period (P = 0.009) among the TdP cases compared with controls. Remarkably, the increase was twice that seen in controls within the first 10 minutes of infusion. A significantly greater increase in the interlead QT dispersion (P = 0.0496) and the intralead QT variability were also observed over the 40 minutes.Conclusion: Our analysis indicates that a rapidly developing and pronounced increase in QTtop duration, a significant increase in interlead QT dispersion, as well as an increased intralead QT variability, characterized patients who developed TdP when treated with an IKr channel‐blocking substance, as compared to identically treated patients without TdP.
Efficacy of Intravenous Atenolol for Prevention of Neurally Mediated Syncope Induced by Head‐Up Tilt Testing
Authors: Ortega Javier , Madrid Antonio H. , Seara Javier G. , Rebollo José M. Gonzalez , Lozano Fernando , Parra Javier , Palma José Luis , Moro Concepción 
Published: October 2006

BackgroundIn our hospital we performed a prospective, randomized, double‐blind, and controlled study on the efficacy of oral atenolol in patients with neurocardiogenic syncope. Fifty patients with clinically diagnosed vasovagal syncope were included.A complete study to discard other possible causes of syncope was performed in all patients. In the first part of this study, before the patients were randomized in two groups to receive either atenolol or placebo, a baseline tilt test with a protocol of 80° during 45 minutes was performed.MethodsAll patients with a positive response (18) underwent an infusion of intravenous atenolol and the test was repeated. Four patients with a positive baseline test did not accept the infusion of that drug and, therefore, were not included in this protocol. Atenolol prevented a second positive tilt in 5 of 18 patients (27.8%).ResultsThere were no significant differences between both groups with respect to age, gender, blood pressure, heart rate, and number of episodes of syncope. Thirteen patients had a recurrent positive response in spite of atenolol. Eleven of these subjects had a syncope during the first tilt test. In seven of these patients (63.6%) atenolol prevented severe symptoms 'syncope) in the second test. In patients with a significant cardioinhibitory response in the first test, atenolol did not prevent a second positive response in any of the patients.ConclusionsIn our study, intravenous atenolol was not an efficient drug to prevent a second positive tilt test in patients with clinically diagnosed vasovagal syncope and a first positive tilt‐table test. Only 5 of 18 patients (27.8%) had a negative response in the second test after the infusion of that drug. This drug was more effective in patients with a vasodepressor or mixed response in the first tilt test. A.N.E. 1999; 4(2):130–136
Circadian Pattern of QT/RR Adaptation in Patients with and Without Sudden Cardiac Death after Myocardial Infarction
Authors: Yi Gang , Guo Xiao Hua , Gallagher Mark M. , Hnatkova Katerina , Reardon Michael , Poloniecki Jan , Camm A. John , Malik Marek 
Published: October 2006

Background:Abnormalities in the adaptation of the QT interval to changes in the RR interval may facilitate the development of ventricular arrhythmias. Methods:This study sought to evaluate the dynamic relation between the QT and RR intervals in patients after acute myocardial infarction. The study population consisted of 14 patients after myocardial infarction (age 60 ± 7 years, 12 men) who died suddenly (SCD victims) within 1 year after the myocardial infarction and 14 pair‐matched age, sex, left ventricular ejection fraction, infarct site, thrombolytic therapy) patients who remained event‐free after myocardial infarction (Ml survivors) for at least 3 years. Fourteen normal subjects were studied as controls (age 55 ± 9 years, 11 men). QT and RR intervals were measured on a beat‐to‐beat basis automatically with a visual control from 24‐hour ambulatory ECGs using Reynolds Pathfinder 700. Mean hourly values of the QT/RR slope (QT =α+βRR) and corrected QT interval at 1000 ms of RR interval (QT1s) were derived for each subject using an inhouse program (QT1s=α+1000β). The dynamics of the QT/RR slope and QT1s were assessed on the basis of hourly mean values. The circadian rhythm of ventricular repolarization (QT1s and QT/RR slope) was examined by harmonic regression analysis. Results:There was a trend towards a significant difference in 24‐hour mean value of QT1s between study groups (408 ± 26 ms vs 381 ± 43 ms and 386 ± 22 ms, P = 0.06), and a significant difference was found between SCD victims and normal subjects (408 ± 26 vs 386 ± 22 ms, P = 0.02). The QT1s differed significantly between study groups (P = 0.038) only during the day time (09:00–19:00 hour), when QT1s was significantly longer in SCD victims than in normal subjects (409 ± 33 vs 380 ± 27 ms, P = 0.02) and tended to be longer than in Ml survivors (409 ± 33 vs 379 ± 42 ms, P = 0.08). The 24‐hour mean value of QT/RR slope was significantly different between study groups (P = 0.04), with a significantly steeper slope in SCD victims than in normal subjects (0.15 ± 0.07 vs 0.09 ± 0.02, P = 0.008). During day time, the QT/RR slope differed significantly between study groups (P = 0.04), while the difference was less marked at night (P = 0.08). The slope was significantly steeper in SCD victims than in normal subjects during both day and night (P < 0.05). A marked circadian variation of QT1s was observed in normal subjects, which was blunted in Ml survivors and SCD victims. Conclusions:Abnormal repolarization behaviors, characterized by longer QT1s and impaired adaptation of QT to variations in RR intervals, were found in SCD victims. Hence, lethal ventricular tachyarrhythmias might be provoked by the altered repolarization dynamics in patients after myocardial infarction. A.N.E. 1999;4(3):286–294
Occurrence and Prognosis of Ventricular Arrhythmia in Men With and Without Asymptomatic Leg Artery Disease: Results from a Prospective Population Study “Men Born in 1914,” Malmö, Sweden
Authors: Hedblad B. , Janzon L. , Ögren M. 
Published: October 2006

Background:The occurrence of frequent or complex ventricular arrhythmia in apparently healthy men during ambulatory ECG recording has been shown to be associated with an increased incidence and mortality in ischemic heart disease. Similar risk has been documented for individuals with asymptomatic leg artery disease. The objective of this follow‐up of 450 men from the prospective cohort study “Men born in 1914” in Malmö, Sweden has been to assess whether there is any relationship between the occurrence of ventricular arrhythmia and asymptomatic leg artery disease and whether the prognosis with regard to survival and incidence of myocardial infarction is different in men with and without asymptomatic leg artery disease.Methods:The ECG was recorded during 24 hours. Mortality and incidence of cardiac events (i.e., acute myocardial infarction and death in chronic ischaemic heart disease) during the 10 years following the baseline examination 1982–1983 has been related to occurrence of frequent or complex ventricular arrhythmia (i.e., Lown class 2–5) and prevalence of asymptomatic leg artery disease (i.e., ankle‐arm blood pressure index, ABPI < 0.9 at rest).Results:There was no association between the prevalence (14% vs 13%) or severity of leg artery disease and the occurrence of ventricular arrhythmia. History of cardiovascular disease was related to both conditions. In men without leg artery disease, occurrence of arrhythmia was associated with an increased mortality rate, from 29.1 to 41.5 per 1000 person‐years (P = 0.046) and cardiac event rate, from 15.6 to 27.1 per 1000 person‐years (P = 0.023). The increased incidence of cardiac events and death associated with arrhythmia was modified by the presence of leg artery disease. There was a low ABPI in the group with arrhythmia associated with an increase in mortality rate from 41.5 to 95.8 per 1000 person‐years and an increase of the cardiac event rate from 27.1 to 76.1 per 1000 person‐years. These associations remained statistically significant after adjustment in the analysis with regard to history of cardiovascular disease and other potential confounders.Conclusions:Occurrence of ventricular arrhythmia is a common condition in apparently healthy elderly men. Although it seems to be equally common in men with and without asymptomatic leg artery disease, with regard to the incidence of cardiac events and death it is associated with a more serious prognosis in men with leg artery disease.A.N.E. 1999;4(3):309–315
Changes in High Frequency QRS Energy in the Signal‐Averaged Electrocardiogram After Acute Experimental Infarction
Authors: Bloomfield Daniel M. , Lander Paul , Steinberg Jonathan S. 
Published: October 2006

Background: The effect of Ml on the high frequency content of the QRS complex in the SAECG remains a matter of controversy. The purpose of this study was (1) to characterize the changes in the high frequency QRS energy that occur after experimental Ml in dogs, (2) to evaluate the change in QRS energy in a number of frequency bandwidths, and (3) to evaluate the relationship between the change in QRS energy and infarct size and location, as well as the inducibility of VT.Methods: MIs were created in 21 dogs by balloon occlusion of the left circumflex (n = 10) or left anterior descending (n = 11) coronary arteries. SAECGs, using three orthogonal leads (X, Y, Z), were obtained before and 4–6 days after the Ml. The vector magnitude was calculated. Using a spectral filter, we calculated the energy in û Vs) of the entire QRS as the integrated area of the signal voltage within a low frequency bandwidth (15–40Hz) and two high frequency bandwidths (40–80 Hz, 80–300 Hz). QRS energy was log transformed to achieve a normal distribution.Results: There was a significant decrease in QRS energy after Ml in the low and high frequency bandwidths in the 21 dogs that was primarily detected in the Y lead. This decrease in high frequency energy after Ml occurred primarily in the dogs with anterior infarction where there was a 13–21% drop in QRS energy in all three bandwidths in the vector magnitude as well as the Y and Z leads (all P > 0.05). This drop in QRS energy after anterior wall Ml was moderately correlated with increasing infarct size in all three bandwidths. There were no consistent changes in QRS energy in the dogs with posterior infarction. The drop in QRS energy after Ml was not associated with inducible VT. The change in QRS energy after Ml in all three bandwidths were highly correlated.Conclusions: The process of Ml produced a decrease in QRS energy, in both low and high frequency bandwidths, that was most consistent in dogs with anterior wall Ml. The decrease in QRS energy after Ml was not associated with inducible VT. Ml produced similar changes in QRS energy in low and high frequency bandwidths. A.N.E. 1999;4(1):72–82
Evaluation of Patients with Palpitations: Cardiac Event Recorder Versus 48‐hour Holter Monitoring
Authors: Makowska Ewa , Szymot Joanna , Soszyriska Malgorzata , Kulakowski Piotr 
Published: October 2006

Objectives: (1) To compare a diagnostic yield of cardiac event recorders with that of 48‐hour Holler monitoring, (2) to determine the etiologies of palpitations, and (3) to assess an optimal duration of using an event recorder by a patient.Background: Palpitation is a common symptom which accounts for 16% of total complaints reported by patients in general medical settings. An ambulatory Holter ECG monitoring or an event recorder can be used to establish the cause of palpitations.Methods: (1)The study group consisted of 33 consecutive patients (24 females, 9 males, mean age 50 ± 32 years) with undiagnosed attacks of palpitations, occurring at least once per month. Each patient was randomly allocated to use either an event monitor or 48‐hour Holler monitoring. The patient kept the event monitor for 4 weeks. After the first monitor was returned, the patient was given the other device.Results: Holter monitoring determined the etiology of palpitations in 11 (33%) patients, and the event recorder in 21 (64%) patients (P = 0.0138). In the whole study group, the etiology of palpitations was disclosed in 23 (70%) patients. The diagnosis was possible using Holler ECG monitoring in only 2 (9%) patients, whereas the event recorder revealed the underlying mechanism of palpitations in 12 (52%) patients (P = 0.0007). In nine (39%) patients both methods were able to disclose the eliology of palpitations. The findings of 117 recordings obtained using an event recorder during palpitations were atrial fibrillation in 10 (9%), narrow QRS tachycardia in 4 (3%), frequent supraventricular eclopy in 17 (15%), frequent ventricular eclopy in 6 (5%), and episodes of palpitations sinus rhythm were recorded in the remaining 80 (68%). Of patients who experienced episodes of palpitations while using an event recorder, the earliest recording was obtained on the first day of the study, and the latest on the 18 day of using the event recorder.Conclusions: (1) The cardiac event recorders yield more diagnoses than 48‐hour Holter monitoring in patients with palpitations occurring at least once per month, (2) in this group of patients the event recorder provided a diagnostic ECG recording during the first 18 days of using the device, and (3) in the majority (57%) of patients a normal sinus rhythm was recorded during episodes of palpitations. A.N.E. 2000;5(4):315–321
Assessment of Cardiac Autonomic Nervous Activities by Means of ECG R‐R Interval Power Spectral Analysis and Cardiac Depolarization‐Repolarization Process
Authors: Ue Hidetoshi , Masuda Izuru , Yoshitake Yasuhide , Inazumi Takanori , Moritani Toshio 
Published: October 2006

Background: Cardiac autonomic dysfunction is prevalent in diabetic patients and associated with prolongation of myocardial repolarization period. It was speculated that changes in autonomic nervous system activity, particularly the sympatho‐vagal balance contributes to the prolongation of myocardial repolarization.Methods: Ten patients with ischemic heart disease (IHD), thirty patients with diabetes mellitus, and ten control subjects (CONT) volunteered for this study. The patients with diabetes mellitus were further divided into three subgroups according to the severity of neuropathy: patients without any neuropathy (NO), with peripheral neuropathy (N1) and with autonomic neuropathy (N2). ECG activation time (AT), activation recovery interval (ARI), and recovery time (RT) was measured and ECG R‐R spectral analysis was performed.Result: There were significant decreases (P < 0.01) in RTc in N1, N2, and IHD as compared with CONT and NO. In addition, HI of R‐R interval power spectrum were significantly decreased (P < 0.01) in N1, N2, and IHD than those in CONT and NO.Conclusion: We have successfully developed and adapted a new computer system for simultaneous ECG RT measurements and ECG R‐R power spectral analysis, a putative index of autonomic dysfunction and risk for sudden cardiac death, to study patients with ischemic heart disease and with varying degrees of diabetic autonomic neuropathy. Those with little HI power, which reflects more severe diabetic neuropathy and a high risk of sudden cardiac death, had significantly longer RTc, which is consistent with sympatho‐vagal imbalance toward parasympathetic denervation.
Wavelet Analysis of Signal‐Averaged Electrocardiograms
Authors: Hnatkova Katerina , Malik Marek , Kulakowski Piotr , Camm A. John 
Published: October 2006

Background:Wavelet representation is able to detect low amplitude patterns even if hidden within signals of much higher amplitudes. Method:A software system has been developed that implements wavelet representation of signal‐averaged electrocardiograms (SAECG). In this system, wavelet analysis leads to 4 numerical parameters that characterize the content of low amplitude perturbations found within the high gain QRS complex. In three substudies, these numerical parameters were compared with the standard time‐domain indices of SAECG. Populations:Normal limits were identified from recordings of 104 normal healthy volunteers (54 males, mean age 50 ± 17 years). Short‐term reproducibility of the numerical indices and of abnormal findings was evaluated in a population of 85 subjects (16 healthy volunteers, 22 patients with documented ventricular tachycardia [VT] without structural heart disease, 30 patients with documented sustained postinfarction VT, and 17 survivors of acute myocardial infarction) who were each recorded three times with 5‐minute periods separating individual recordings. The power of wavelet and time‐domain analyses in distinguishing patients with and without sustained VT after myocardial infarction was assessed using recordings of 53 patients with postinfarction VT and of 53 age, sex, and infarct site matched patients without a history of arrhythmic complications after infarction. Results:The studies have shown that (a) the indices of wavelet analysis are more reproducible than the time‐domain indices, (b) the distinction between patients with and without VT after myocardial infarction is similarly powerful by wavelet and time‐domain analyses, and the association of the positive SAECG analysis with postinfarction VT is highly significant with both analyses (P = 3.94 × 10–14 for wavelet analysis and 2.55 × 10−9 for time‐domain analysis), the indices of wavelet analysis differ significantly between normals and patients with an uncomplicated history of myocardial infarction (P = 0.02–0.005), while time‐domain indices do not (all parameters NS), (d) in contrast to the time‐domain analysis, wavelet analysis was similarly powerful in identifying VT patients with anterior and inferior infarction (P = 1.4 × 10−9, n = 30, and P = 2.0 × 10−15, n = 23, respectively). Conclusion:Wavelet analysis is a highly reproducible method for SAECG processing which (a) is as powerful as the time‐domain analysis for the identification of ischemic VT patients, (b) compared to the time‐domain analysis, is not dependent on infarct site, and is able to distinguish postmyocardial infarction patients without VT from healthy subjects. A.N.E. 2000,5(1):4–19
Comparison of Various Measures of Optimum Atrial Timing in Patients with Dual Chamber Pacemakers
Authors: Pai Sudha M. , Jacobson Alan K. , Pai Ramdas G. 
Published: October 2006

Background:In patients with dual chamber pacemakers, the optimal AV delay is highly variable. This study examines the alternative measures of optimum atrial timing and the factors responsible for the marked variability in the optimal AV delay. Methods and results:Twelve patients with dual chamber pacemakers were studied. The AV delay was varied from 25 to 250 ms in 25‐ms increments and at each stage, mitral, tricuspid, and aortic flows were recorded using the Doppler technique. The optimum AV delay varied from 75 to 175 ms (146 ± 37 ms). At optimum AV delay, both the E and A waves of the transmitral flow were partially fused, eliminating diastasis with a fusion velocity of 27 ± 14 cm/s. The stroke distance was lower when the E and A waves were not fused at shorter AVD, despite a longer diastolic filling period, or fully fused at a longer AVD, which also the shortened diastolic filling period. At optimum AV delay, the E/A velocity ratio was 0.74 ± 0.15, reflecting slight atrial predominance of LV filling. The optimum timing of atrial contraction was better defined in terms of its relation to LV ejection (175 ± 31 ms before LV ejection), and this had a smaller coefficient of variation than optimum AV delay. This interval, unlike the AV delay, was not affected by interatrial and interventricular conduction times. Conclusions:In this older population of patients with dual chamber pacemakers without significant valvular heart disease, the effective LA contraction in relation to LV ejection is a better measure of atrial timing than the programmed AV delay which is affected by atrial and ventricular conduction times. A.N.E. 2000;5(1):68–72