bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence‐Based Understanding of Medication‐Overuse Headache: Clinical Implications
Authors: Dodick David , Freitag Frederick
Published: October 2006

This article discusses the problem of medication‐overuse headache from a variety of perspectives, based on the best available evidence. This presentation clarifies the definition of the disorder, distinguishing it from alternative terminology, and describes its epidemiology, natural history, and clinical course. Antimigraine medications are believed to differ in their relative liability to contribute to the development of medication‐overuse headache. Patients most at risk of developing medication‐overuse headache need to be identified so that appropriate preventive measures can be initiated.
A novel IGnT allele responsible for the adult i phenotype
Authors: Lin Marie , Hou Min‐Ju , Yu Lung‐Chih
Published: October 2006

BACKGROUND: The adult i phenotype has been characterized as the presence of a very low level of I antigen but a high quantity of I antigen on red blood cells (RBCs). It has been noted that this rare phenotype is partially associated with congenital cataracts. It has been demonstrated that the human I locus expresses three IGnT forms, IGnTA, IGnTB, and IGnTC, and that the IGnTC gene is responsible for the I antigen expression on RBCs. This report describes molecular genetic analysis of a Taiwanese person with the adult i phenotype but without congenital cataracts.

STUDY DESIGN AND METHODS: The five exon regions of the IGnT gene of the adult i individual were amplified by polymerase chain reaction (PCR) and cloned, and the sequences were determined. The activity of the IGnT enzyme expressed from the mutant IGnTC gene identified in this i adult was analyzed.

RESULTS: The presented adult i individual possesses wild‐type IGnTA and IGnTB genes but a mutant IGnTC gene with a 243T>A nucleotide substitution, which predicts an amino acid alteration of Asn81Lys. PCR‐restriction fragment length polymorphism analysis has been used to show that this IGnTC*243A allele is uncommon in the general Taiwanese population. The activity of the IGnT enzyme expressed from the mutant IGnTC*243A gene was significantly reduced when compared with that expressed from the wild‐type IGnTC gene.

CONCLUSION: A novel IGnTC allele with a 243T>A missense mutation was demonstrated in our adult i Taiwanese without congenital cataracts. The molecular basis revealed for this adult i case agrees with the proposed molecular genetic mechanism, accounting for the partial association of the adult i phenotype with congenital cataracts.
Relationship Between Ventricular Rate Variability in Nonsustained Ventricular Tachycardia and Subsequent Cardiac Events
Authors: Dabrowski Andrzej , Piotrowicz Ryszard
Published: October 2006

Background: Clinical and experimental observations indicate that reduced beat‐to‐beat changes in the cycle length of nonsustained ventricular tachycardia (NSVT) may portend malignant ventricular tachyarrhythmias and sudden cardiac death. The purpose of the study was to test the hypothesis that measures of ventricular rate variability during NSVT (VRV‐NSVT) may be useful in identifying patients at high risk of life‐threatening arrhythmic events.

Methods: The study group consisted of 326 patients who had NSVT on 24‐hour ECG recordings. Temporal changes in up to 10 beat‐to‐beat intervals of NSVT runs (V‐V) were assessed. The following parameters of VRV‐NSVT were calculated: (1) average value of successive differences in V‐V intervals (ADVV); and (2) normalized average value of successive differences in V‐V intervals (nADVV).

Results: During a mean follow‐up of 4 years, 52 (16%) patients had a documented episode of sustained VT or ventricular fibrillation. Patients with these arrhythmic events had significantly (P < 0.001) lower values of ADVV and nADVV variables in comparison to patients without arrhythmic events. The relative risk of malignant arrhythmic events for patients with ADW < 40 ms was 4.9 (P < 0.001), for patients with nADVV < 6%, the risk was 3.9 (P < 0.001).

Conclusions: The results of this study indicate a strong and significant relationship between NSVT and the risk of subsequent malignant ventricular tachycardia. The assessment of VRV‐NSVT may be useful for identifying patients at high and low risk for subsequent arrhythmic events.
Frequency Response Characteristics Required for Detection of T‐Wave Alternans During Ambulatory ECG Monitoring
Authors: Hearing Bruce D. , Stone Peter H. , Verrier Richard L.
Published: October 2006

Background: T‐wave alternans has been increasingly implicated as a potential marker of vulnerability to ventricular tachyarrhythmias in both experimental and clinical investigations. However, the suitability of ambulatory ECG (AECG) recorders for monitoring this parameter has not been systematically studied.

Methods: We evaluated the frequency response characteristics and performance in monitoring a computer simulated alternans signal in three brands of amplitude‐modulated (AM) and one frequency‐modulated (FM) recorder and compared the results to those of the reference digital AECG unit.

Results: A common feature of the AM recorders was distortion due to electronic head resonance, particularly at heart rates in the range of 60–100 beats/min. The maximum distortion of T‐wave morphology by the AM units was —6% to +28%.

Conclusions: We conclude that digital and FM recorders are preferable for AECG monitoring of T‐wave alternans. AM recorders can be used if the distortion is not excessive.
T‐Wave Alternans During Ambulatory Ischemia in Patients with Stable Coronary Disease
Authors: Verrier Richard L. , Hearing Bruce D. , MacCallum Gail , Stone Peter H.
Published: October 2006

Background: T‐wave alternans is a marker of vulnerability to ventricular tachyarrhythmias and has been documented during myocardial ischemia associated with angioplasty, bypass graft occlusion, and episodes of Prinzmetal's variant angina. We examined whether this phenomenon was present during ambulatory ischemia in ten patients randomly selected from the placebo phase of the Angina and Silent Ischemia Study [ASIS].

Methods: The eligibility criteria for participation in the ASIS study were stable coronary disease, a positive exercise stress test, and verified ischemic episodes during ambulatory ECG (AECG) monitoring. For each patient, one ischemic episode was analyzed which met the criteria of > 2‐mm ST segment depression for > 3 minutes with a relatively stable ST segment baseline of > 1 hour preceding the index episode. T‐wave alternans was measured using the spectral analytical technique of complex demodulation.

Results: In the stable coronary patients of the ASIS trial, we found that T‐wave alternans magnitude nearly tripled from 0.27 ± 0.02 mV × ms before ischemia onset to 0.77 ± 0.08 mV × ms (P < 0.01) during ischemic episodes. Heart rates ranged from 83 ± 2.9 beats/min prior to ischemia to 116 ± 2.5 beats/min during ischemia (P < 0.01). There was no statistical correlation between the magnitude of the ST segment depression > 2 mm and the ischemia‐induced increase in T‐wave alternans.

Conclusions: We conclude that T‐wave alternans often occurs in association with ambulatory ischemia. Thus, risk assessment in stable coronary patients may be enhanced by monitoring both ST segment deviation and T‐wave alternans as they measure relevant but fundamentally different electrophysiological properties.
Time‐Frequency Analysis of Heart Rate Variability
Authors: Birand Ahmet , Saliu Sokol , Kudaiberdieva Gulmira Z.
Published: October 2006

Background: The heart rate variability (HRV) signal is mainly analyzed in frequency‐domain and the signal's spectrum is estimated using either Fast Fourier Transformation (FFT) or the autoregressive (AR) model. These two methods assume that the HRV signal is stationary and additionally the AR method is based on the assumption that the model is linear and the signal is monocomponent in nature. Qualities of spectral estimates are thus closely related to the validity of the above assumptions. Evidence has accumulated indicating that HRV is a multicomponent, nonlinear and nonstationary signal. Then the spectral representations currently used would yield global, approximate, and smoothed view of HRV dynamics.

Methods: We applied time‐frequency (TF) analysis methods, smoothed pseudo‐Wigner distribution (SPWD), and spectrogram and complemented for validation by FT spectrum to the HRV signal of fifteen apparently healthy volunteers (mean age 27.2 ± 5.6 years). Short‐term electrocardiograms (ECG) were recorded during supine and upright tilting positions (baseline recording). After baseline recording we induced parasympathetic, sympathetic, and total autonomic blockade correspondingly to six, nine, and four subjects. In addition, in four patients ECGs were recorded during controlled respiration.

Results: SPWD and spectrogram revealed strips in frequency, or TF components, corresponding to FT components. High frequency (HF) components appeared stationary (in wide sense), with slight mean frequency shifts during spontaneous respiration, concurrent with respiratory motions. Low frequency (LF) and very low frequency (VLF) components had a nonstationary character displaying activity burst in time and interrelation in frequency. Upright tilting caused a uniform reduction in intensity and bandwidth of the HF component and enhancement of intensity and burst activity of the LF component. There was a pronounced decline of HF and LF components’intensity and decrease of HF component's bandwidth after parasympathetic blockade and total autonomic blockade, while the VLF component did not change. Sympathetic blockade was accompanied by augmentation of the LF and HF components’intensity associated with an increase in the HF component's bandwidth and the spreading of it in the region between the LF and HF. The LF component exhibited less burst activity during tilting under sympathetic blockade, as compared to baseline recordings during tilt. The VLF component's behavior did not change after sympathetic, parasympathetic, and total autonomic blockades.

Conclusion: Application of TF distributions to the HRV signal offers a new representation of HRV dynamics. SPWD unveiled features in the HRV signal not available in separate time‐ and frequency‐domains. TF components display idiosyncratic behavior patterns in time and were effected by physiological and pharmacological interventions. A.N.E. 1996;1(4):411–418
Predictive Value of QT Dispersion for Ventricular Tachyarrhythmias in Patients with Implantable Cardioverter Defibrillator
Authors: Grimm Wolfram , Steder Ulrike , Menz Volker , Maisch Bernhard
Published: October 2006

Background: QT dispersion, measured as interlead variability of QT intervals in the surface electrocardiogram, has been demonstrated to provide an indirect measurement of the inhomogeneity of myocardial repolarization as a potential substrate for ventricular arrhythmias.

Methods: QT dispersion was measured in the standard 12‐lead ECG in 51 patients at the time of implantation of a third generation implantable cardioverter defibrillator (ICD) with automatic electrogram storage capability for electrical events triggering device therapy. In addition, QT dispersion was measured in 100 age‐ and sex‐matched healthy controls. All 5 1 study patients with ICD were prospectively followed to determine possible associations between QT dispersion at implant and subsequent spontaneous ICD shocks for ventricular tachyarrhythmias (VT).

Results: Rate‐corrected QT dispersion and adjusted QTc dispersion, which takes account of the number of leads measured, were significantly greater in ICD patients compared to controls (76 ± 25 ms vs 46 ± 11 ms, and 24 ± 7 ms vs 14 ± 3 ms respectively, P < 0.0 1). During 15 ± 8 months follow‐up, ventricular tachyarrhythmias occurred in 23 (45%) of 51 ICD patients. QTc dispersion and adjusted QTc dispersion were not significantly different between ICD patients with ventricular tachyarrhythmias and ICD patients without ventricular tachyarrhythmias during follow‐up (74 ± 19 ms versus 77 ± 29 ms, and 23 ± 6 ms vs 25 ± 8 ms respectively).

Conclusion: Increased QT dispersion measured in the 12‐lead standard ECG does not appear to be a useful marker for future arrhythmic events in a mixed patient population with ICD.
Reexamination of the Roles of Beta‐Endorphin and Cardiac Autonomic Function in Exercise‐Induced Silent Myocardial Ischemia
Authors: Hikita Hiroyuki , Kurita Akira , Takase Bonpei , Nakamura Haruo
Published: October 2006

Background

Anginal pain perception has been reported to be modulated by endogenous opiates, or peripherally as a result of neuropathy. However, whether these factors can contribute to the mechanisms of silent myocardial ischemia remains unclear.

Methods

Based on the results of previous exercise testing, a total of 140 patients (39 diabetic and 101 nondiabetic) with exercise‐induced myocardial ischemia were divided into the following four groups: 19 diabetics with silent myocardial ischemia; 49 nondiabetics with silent myocardial ischemia; 20 diabetics with anginal symptoms; and 52 nondiabetics with anginal symptoms. All patients underwent treadmill exercise testing and 24‐hour ambulatory electrocardiographic recording. Plasma beta‐endorphin levels and tactile thresholds were measured before and during exercise. With regard to the ambulatory electrocardiographic recording, the mean of the standard deviations (SDNNIDX) of all normal sinus RR intervals during successive 5‐minute recording periods over 24 hours was analyzed and considered as an index of the autonomic function.

Results

The plasma beta‐endorphin level during exercise was significantly greater in nondiabetic patients with silent myocardial ischemia than in diabetics with silent myocardial ischemia and in nondiabetics with anginal symptoms. The SDNNIDX mean was significantly less in diabetics with silent myocardial ischemia than in diabetics with anginal symptoms; in nondiabetics with anginal symptoms; and in nondiabetics with silent myocardial ischemia.

Conclusions

We confirm that elevated beta‐endorphin levels are associated with silent myocardial ischemia in nondiabetic patients and that abnormalities in autonomic function seen in diabetes are associated with the silent form of myocardial ischemia. A.N.E. 1997;2(4):319–325
Signal‐Averaged Electrocardiogram: Update 1997
Authors: Mäkijärvi M. , Breithardt G. , Reinhardt L. , Fetsch T. , Borggrefe M. , Martinez‐Rubio A.
Published: October 2006

Background

During the last 10 years, the signal‐averaged electrocardiographic (SAECG) method has been proposed for a growing amount of clinical applications. As a screening method for increased risk of life‐threatening ventricular arrhythmias it has demonstrated its value especially in risk stratification after myocardial infarction (Ml) and in the evaluation of patients with unexplained syncope. Its value in risk prediction is now also proven in patients treated with thrombolytic therapy.

Methods

In patients with dilated cardiomyopathy, hypertrophic cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy, the SAECG is helpful for detecting propensity to spontaneous ventricular tachycardia. P wave signal averaging has been demonstrated to identify patients with propensity to atrial arrhythmias, especially atrial fibrillation. Also, the diagnosis of sick sinus syndrome can be enhanced using this method.

Results

So far, the use of SAECG in other patient populations except coronary heart disease has been very limited. However, the results of the recent studies recommend the utilization of this technique also in children and in the elderly, adjusting the findings with the effects of body size and age on the SAECG.

Conclusions

The SAECG has a definite independent role in improving the predictive accuracy of conventional risk‐evaluation techniques in patients with Ml or cardiomyopathy. New patient populations like children and the elderly enlarge the number of patients benefiting of this method. New clinical applications of the SAECG method, such as detection of the propensity to atrial arrhythmias, ischemia and drug effects, are currently merging. Combining the time‐ and frequencydomain analysis of the SAECG with other methods relevant for the clinical problem is the way to optimize the use of this sophisticated noninvasive technique in clinical practice.
Effect of Repetitive, Transient Coronary Occlusions During Percutaneous Transluminal Angioplasty on Autonomic Cardiac Control
Authors: Limbruno Ugo , Strata Giancarlo , Petronio Anna Sonia , Baglini Roberto , Di Santo Domenica , Amoroso Giovanni , Zucchi Riccardo , Balbarini Alberto , Mariani Mario
Published: October 2006

Background: Previous findings suggest that transient myocardial ischemia and reperfusion may elicit changes in the autonomic balance. In this study, a spectral analysis of heart rate variability was used to assess the modifications of sympathovagal balance induced by coronary angioplasty and their relationship with the occlusion site.

Methods: We studied 23 patients (17M, 6F, age 58 ± 10 years) with left anterior descending and 19 patients (15M, 4F, age 56 ± 9 years) with right coronary artery stenosis. Spectral analysis of heart rate variability was performed, by autoregressive model, in basal conditions and during each balloon inflation. At least two inflations of 90–120 seconds were performed in each patient.

Results: In patients with left anterior descending artery stenosis, the first occlusion induced marked changes in the autonomic balance, which moved toward a sympathetic predominance. The low frequency component of the spectrum and the low‐to‐high frequency ratio increased from 59 ± 10 normalized units (NU) to 75 ± 10 NU (P < 0.001) and from 2.4 ± 1.4 to 7.3 ± 4.7 (P < 0.001) respectively, while the high frequency component decreased from 30 ± 11 NU to 14 ± 7 NU (P < 0.001). These changes showed a progressive attenuation during repetitive occlusions, and were significantly correlated with the entity of myocardial ischemia assessed by the ST‐segment shift measured on the intracoronary electrocardiographic lead. On the contrary, in patients with right coronary artery stenosis the first occlusion was ineffective with regard to the spectral parameters whereas the third occlusion induced a significant increase in the high frequency component (from 31 ± 9 NU to 41 ± 10 NU, P < 0.01) and decrease in the low‐to‐high frequency ratio (from 2.1 ± 0.9 to 1.3 ± 0.5, P < 0.05) suggesting a vagal activation. The entity of vagal activation was not correlated with the ST‐segment shift.

Conclusions: Our data indicate that repetitive coronary occlusions induce significant changes in the autonomic balance. The direction and the time course of these changes are related to the occlusion site.
Circadian Variation and Waking Hour Dynamics of the QT Interval
Authors: Singh Jagmeet P. , Johnston Jim , Sleight Peter , Marinho Maria F. , Kulangara Sara , Casadei Barbara , Hart George
Published: October 2006

Background: The incidence of sudden cardiac death is maximal in the morning hours. Although ventricular arrhythmias have been implicated as a potential mechanism, and several neurohumoral factors affecting myocardial excitability have been shown to be raised in the early morning hours, it is not known if there is any circadian variation in the dynamics of ventricular repolarization when studied on a beat‐to‐beat basis. The objective of this study was to examine the range, diurnal variations, and circadian distribution of the variability of the QT interval in healthy subjects.

Method: We developed and validated a new method for continuous measurement of QT intervals from 24‐hour Holter recordings. The QT intervals measured semi‐automatically were corrected by a linear regression formula derived independently for each patient from his own QT and RR values in 32 healthy males (20 ± 0.4 years). QT variability was assessed by the mean standard deviation of the average of consecutive uncorrected QT intervals (SDA‐QT Index) and corrected QT intervals (SDA‐QTc index) over 5‐minute segments. The rate‐dependent changes of the QT interval were studied as a function of the slope of the regression line between the QT and RR values.

Results: The average QTc range was mean (SD) 79 (± 28) ms; the average maximal QTc interval was 481 (± 24) ms. The 95% upper confidence limit for the mean 24‐hour QTc interval was 443 ms. The RR, QT, and QTc intervals were longer, while the SDA‐QT and SDA‐QTc indices were shorter during sleep. Hourly averages of the SDA‐QT and SDA‐ QTc index revealed a sudden increase in QT variability in the first hour of waking (P < 0.0001 and P = 0.006).

Conclusion: The dynamic behavior of the QT interval shows significant diurnal variations. The maximal QTc interval over 24 hours is longer than previously assumed. The period shortly following awakening is characterized by a peak in the variability of the QT interval. These changes may be indicative of autonomic instability during the early waking hours and correspond with the peak incidence of sudden arrhythmic death.
Twelve‐Lead QT Dispersion Is Smaller In Women Than In Men
Authors: Challapalli Sridevi , Lingamneni Rajeswari , Horvath George , Parker Michele , Goldberger Jeffrey J. , Kadish Alan H.
Published: October 2006

Background

Although gender differences in the corrected QT interval (QTc) have been described, gender differences in QT dispersion (QTd) have not been carefully evaluated. This study was designed to measure QTd in 22 young healthy women and in 20 healthy men.

Methods and Results

Twelve‐lead ECGs were recorded at rest and following double autonomic blockade with atropine 0.04 mg/kg and propranolol 0.2 mg/kg during the menstrual, follicular, and luteal phases of the menstrual cycle, which was confirmed by hormone levels. Men were studied during three separate visits as controls. In women, there was no difference in QTd among the three phases of the menstrual cycle, and thus all three visits were pooled for comparison with men. The 12‐lead QT dispersion (maximum — minimum QT) was larger in men than in women at baseline (41 ± 17 ms vs 35 ± 16 ms), and this difference tended to decrease after double autonomic blockade (35 ± 14 ms vs 32 ± 11 ms). The standard deviation of the QT interval across the 12 leads was larger in men than in women at baseline (12.6 ± 4.5 vs 10.8 ± 4.1), and this difference was no longer significant after double autonomic blockade (10.4 ± 4.4 vs 10.1 ± 3.5). QT dispersion was significantly reduced by autonomic blockade (P < 0.05).

Conclusions

(1) Double autonomic blockade slightly reduces QTd. (2) QTd is higher in men than in women at baseline but more similar after autonomic blockade. These findings may contribute to the gender difference in the corrected QT interval. (3) Increased female QTd is not the mechanism of increased female susceptibility to torsade de pointes. The clinical implications of gender differences in QTd and QTc remain to be defined. A.N.E. 1998; 3(1):25–31
Spatial Dispersion of the Magnetocardiographically Determined QT Interval and Its Components in the Identification of Patients at Risk for Arrhythmia after Myocardial Infarction
Authors: Hailer Birgit , Van Leeuwen Peter , Lange Silke , Gronemeyer Dietrich , Wehr Michael
Published: October 2006

Background

Aim was the examination of the spatial distribution of QT interval in patients after Ml with and without VT. Analysis of the QT interval components was undertaken to identify those repolarization patterns that contribute essentially to heterogeneity of recovery times.

Methods

Multichannel magnetocardiography was performed in 10 healthy subjects as well as in 18 patients after Ml of whom 8 had experienced clinical episodes of sustained VT in a period up to 4 years after Ml. For each subject, the temporal dispersion of the intervals QT, QRS, JT apex, T apex‐T offset, and QT apex was calculated as the difference between its minimal and maximal value. The spatial dispersion of each interval was examined visually by plotting the deviations of each channel from the minimal value with respect to its position. Local and global spatial variability was quantified using two smoothness indices, SI and Sin.

Results

Dispersion and smoothness values for all intervals were generally significantly lower in the control group. When comparing patients with and without VT, dispersion values could not separate between patient groups. In contrast, SI and Sin values were significantly different, the VT group demonstrating higher values for QT, JT apex, and QT apex (P < 0.05).

Conclusion

Spatial analysis of the dispersion of cardiac time intervals is a better marker for increased risk for malignant arrhythmia than the strictly temporal approach using standard dispersion measures. In particular the results suggest that the heterogeneity of repolarization is the greatest during the interval between QRS offset and T apex.
The Potential Impact of Prehospital Electrocardiography and Telemetry on Time to Thrombolysis in a United Kingdom Center
Authors: Melville Martin R. , Gray David , Hinchley Malcolm
Published: October 2006

Background

Despite efforts to modify patient attitudes, prehospital, and in‐hospital factors, the median symptom‐to‐needle and door‐to‐needle time to thrombolysis remains unacceptably long for patients experiencing the symptoms of acute myocardial infarction (AMI) in University Hospital, Nottingham.

In order to circumvent avoidable in‐hospital delays, we evaluated the use of equipment undergoing field tests with the Nottingham ambulance crew that can record and transmit 12‐lead ECGs to the Coronary Care Unit (CCU) from the patient's home, and so enable the identification of patients with AMI who might be appropriate for direct admission to the unit.

Methods

From November 1996, for 3 months, ambulance crews recorded ECGs on all patients with chest pain suggestive of AMI. These were transmitted to and assessed by coronary care nursing staff who decided whether they satisfied existing criteria for thrombolysis, and arranged direct admission to CCU. Door‐to‐needle times were recorded for those patients thrombolysed as a result.

Results

One hundred consecutive ECGs were transmitted. Twenty‐two showed evidence of AMI resulting in direct admission. Of these, 17 (61%) had a final diagnosis of AMI. Eleven (65%) were eligible for thrombolysis, their median door‐to‐needle time being reduced by 60 minutes. The remaining 78 patients were taken to the Casualty Department for further assessment.

Conclusions

ECG 12‐lead telemetry could make a significant reduction on chest pain to needle time, reducing delay by at least 1 hour, and has the potential to facilitate out‐of‐hospital thrombolysis.
Usefulness of Holter Recordings in the Evaluation of Pacemaker Function: Standard Techniques and Intracardiac Recordings
Authors: Barold S. Serge
Published: October 2006

A dedicated pacemaker Holter system facilitates recognition of the pacemaker stimulus by amplifying and displaying it in an ECG channel without any other data. Such a Holter pacemaker channel may occasionally generate electrostatic charges that produce deflections resembling pacemaker stimuli (pseudopacemaker spikes) arising from a loose ECG electrode, crushed tape, or a dirty recording head. False‐positive spikes or spurious marker deflections in Holter pacemaker channels and occasional failure to detect tiny bipolar stimuli can present challenging problems in the interpretation of pacemaker function. In multiple‐channel recorders, skewing of the recording heads may lead to timing errors and puzzling recordings when one of the ECG or pacemaker channels lags behind others producing asynchrony or malalignment in simultaneously recorded tracings.

The interpretation of Holter recordings from contemporary complex pacemakers requires knowledge of pacemaker timing cycles and their interrelationships, a large variety of programmable parameters or functions, behavior of the nonatrial sensor or sensors in rate‐adaptive systems, device‐specific responses to protect the system from a variety of undesirable situations, and an appreciation of pacemaker eccentricities.

There are a few prospective studies on the value of routine Holter recordings in pacemaker patients. The real value of Holter recordings lies with symptomatic patients when symptoms occur during the recording period. Correlation between symptoms and occasional abnormality of pacemaker function during Holter monitoring remains poorly characterized. The cause of the symptoms is frequently unrelated to the pacemaker system and may not be related to coexisting arrhythmias. In asymptomatic patients, Holter recordings are particularly useful to uncover a lead problem after an unrevealing thorough investigation in the pacemaker clinic.

Special instrumentation was recently developed to register telemetry data from implanted pacemakers simultaneously with ambulatory electrocardiography. In this way, diagnostic marker signals and/or intracardiac electrograms transmitted from the pacemaker can be recorded continuously for 24 hours by a Holter recorder. Advanced technology involving the memory capability of pacemakers will transform the pacemaker itself into a 24‐hour Holter recorder, probably in 4 to 5 years. At present, the memory for storage of intracardiac electrograms is limited from a few seconds to less than a minute according to the manufacturer, but even such mini‐Holter recordings can be diagnostically important.
QT Measurement: A Comparison of Three Simple Methods
Authors: Tran Hieu T. , Fan Chengde , Tu Wei Q. , Kertland Heather , Li Li , Kluger Jeffrey , Chow Moses S.S.
Published: October 2006

Background: QT interval and QT dispersion are useful noninvasive measurements in clinical cardiology and can be measured by several methods. The comparative variability of these methods, however, is not well defined.

Methods: We evaluated the intra‐ and interobserver variability of three simple methods of QT measurement: (1) ruler method: use of a 0.5‐mm scale precision ruler to measure QT with end of T wave determined by extrapolating its slope to baseline; (2) caliper method: use of a standard electrocardiogram (ECG) caliper and the standard ECG paper scale with QT determined by visual inspection; (3) computer method: use of a digitized computer software program with QT determined by cursor set manually by the user. QT intervals from 11 patients (total 44 ECG leads) in sinus rhythm without conduction defect were measured by five blinded, trained observers at two time points (a week apart) in a crossover manner.

Results: The mean difference in intraobserver measurements were 6 ± 2, 12 ± 12, and 27 ± 2 ms by the ruler, caliper, and computer methods, respectively (P > 0.01, ruler vs caliper or computer). The mean differences in interobserver measurements were 13 ± 3, 16 ± 4, and 29 ± 3 ms for the same methods, respectively (P > 0.01, ruler vs caliper, computer). Enlargement of the ECG to 200% did not reduce the measurement variability.

Conclusion: The ruler method as described yielded the lowest variability in QT measurement.
Significance of the Accuracy of RR Interval Detection for the Analysis of New Dynamic Measures of Heart Rate Variability
Authors: Tapanainen Jari M. , Seppänen Tapio , Laukkanen Raija , Loimaala Antti , Huikuri Heikki V.
Published: October 2006

Background: Interest in the analysis of RR interval variability by new dynamic methods is growing, because these methods give different, complementary information on heart rate behavior compared to the traditional measures of HRV. Several new methods have been recently introduced for studying complex heart rate dynamics, but the validity of these methods in analyzing RR interval behavior from Holter recordings is not well established.

Methods: A real‐time microprocessor QRS detector system using a 1‐ms timing accuracy and a conventional 24‐hour ECG recording system with a sampling frequency of 128 Hz were compared in the measurement of new dynamic components of HRV in a sample of ten healthy subjects and ten patients with acute Ml.

Results: Significant errors were observed in the analysis of approximate entropy (ApEn; mean difference 11 %) and in the short‐term scaling exponent value a1 (mean difference 3%) in detrended fluctuation analysis (DFA). In the Poincaré analysis, notable differences were also observed in short‐term instantaneous RR‐interval variability (SD1; mean difference 5%). In spectral analysis, low‐to‐high frequency ratio was also influenced by the sampling frequency (mean difference 14%). The magnitude of all these differences grew proportionately when the overall heart HRV diminished.

Conclusions: The data suggest that conventional Holter recordings should be used with caution in the analysis of new dynamic HRV parameters, especially approximate entropy and the ratio between low and high frequency spectral components, particularly in patient populations with low total HRV.
The Effect of Left Ventricular Function on QT Dispersion in Postmyocardial Infarction Patients with Previous Ventricular Tachyarrhythmias
Authors: Kluger Jeffrey , Giedrimiene Dalia , White C. Michael
Published: October 2006

Objectives: To determine if the presence of left ventricular dysfunction increases the QT and QTc dispersion in postmyocardial infarction patients with ventricular tachyarrhythmias and to determine if left ventricular infarct location is associated with differences in QT and QTc dispersion.

Methods: The data was gathered from a retrospective electrophysiology (EP) database. All postinfarction patients (n = 87) with a past medical history of left ventricular myocardial infarction and ventricular tachyarrhythmia at baseline without bundle branch block or other intraventricular conduction abnormality were included. Patients were separated into those with an LVEF < 40% or < 40%. For secondary analysis, patients were separated into groups based on the location of the infarction. The QT and R‐R intervals were determined from each lead of a 12‐lead electrocardiogram (ECG) taken during the baseline EP study. The shortest QT and QTc intervals were subtracted from the longest intervals on the 12‐lead ECG to give the QT and QTc dispersions.

Results: The QT and QTc interval dispersions were significantly greater among patients with an LVEF < 40% than among those with an LVEF < 40% (57.3 ± 28.2 vs 47.4 ± 17.7, P = 0.05; 64.5 ± 32.1 vs 48.8 ± 18.2. P = 0.005, respectively). No differences in QT or QTc dispersion were noted between patients with anterior or inferior myocardial infarctions.

Conclusions: A higher QT dispersion can be predicted in patients with left ventricular dysfunction, but the location of the myocardial infarction does not predict the QT dispersion.
Variability in the Manifestation of Pre‐excited Atrial Fibrillation: Its Quantification, Theoretical Origin, and Diagnostic Potential
Authors: Lau Ernest W. , Ng G. André , Griffith Michael J.
Published: October 2006

Background: Irregular broad complex tachycardia (BCT) may be due to atrial fibrillation (AF) occurring in the presence of ventricular pre‐excitation (pre‐excited AF) or bundle branch block (BBB‐AF). While irregularity is a defining characteristic of AF. it is a common subjective impression that greater variability in manifestation exists for pre‐excited AF than BBB‐AF. This difference can potentially be exploited for distinguishing the two conditions it some means can be found to quantify it.

Methods: For each of 75 ECGs showing irregular BCT (41 pre‐excited AF and 34 BBB‐AF), a random sample of 10 distinct QRS complexes were selected for quantitative measurement of variability in manifestation, which included the standard deviation (SD) of the width, the SD of the axis, and the coefficient of variation (CV) of the amplitude of the QRS complex.

Results: Pre‐excited AF showed statistically significantly greater values than BBB‐AF with respect to these measures, and receiver‐operating characteristic curves showed that these differences could be useful for their discrimination. For the SD of QRS width, a cut‐off value of 8 ms appeared optimal (sensitivity 1.00 and specificity 0.79). For the SD of QRS axis, a cut‐off value of 2.5 degrees appeared optimal (sensitivity 0.84 and specificity 0.56). For the CV of QRS amplitude, a cut‐off value of 0.10 appeared optimal (sensitivity 0.82 and specificity 0.76).

Conclusions: Pre‐excited AF demonstrated greater variability than BBB‐AF in manifestation. The measures of variability developed can potentially be useful for diagnosing irregular BCT in practice, especially in the context of automated computer‐aided diagnosis. A.N.E. 2001;6(2):117–122
An Evaluation of the Impact of Gender and Age on QT Dispersion in Healthy Subjects
Authors: Tran Hieu , White C. Michael , Chow Moses S.S. , Kluger Jeffrey
Published: October 2006

Objectives: To determine if gender, age, and gender per age category, have an impact on QT and QTc dispersion in healthy volunteers.

Methods: This study was undertaken in 150 patients (50 per age group, 75 males, 75 females). The age groups included young (20–40 years), middle‐aged (41–69 years) and elderly (> 70 years) subjects. The QT intervals on a 12 lead ECG were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QTc interval from the longest on each 12‐lead recording.

Results: Males had higher QT dispersion than females (50 ± 22 vs 42 ± 18 ms, P = 0.017) but QTc dispersion was not significantly changed. No significant differences were seen among the different age categories for QT or QTc dispersion. In elderly subjects, males had higher QT and QTc dispersion than females (54 ± 23 vs 42 ±15 ms, P = 0.039 and 63 ± 23.7 vs 48 ± 21 ms, P = 0.032, respectively).

Conclusions: When evaluating the effect of gender in different age categories, elderly males have significantly greater QT and QTc dispersion than elderly female subjects. No other gender differences were noted for QT or QTc dispersion in the other two age categories. When evaluating a population of healthy volunteers, regardless of age, gender has an impact on QT dispersion but no significant interaction with QTc dispersion. Evaluating age without dividing the data by gender yields no significant differences in QT or QTc dispersion. A.N.E. 2001;6(2):129–133
Is QT Dispersion Associated with Sudden Cardiac Death in Patients with Hypertrophic Cardiomyopathy?
Authors: Yi Gang , Poloniecki Jan , Dickie Shaughan , Elliott Perry M. , Malik Marek , McKenna William J.
Published: October 2006

QT dispersion is significantly greater in patients with hypertrophic cardiomyopathy (HCM) than that in healthy subjects. Few data exist regarding the prognostic value of QT dispersion in HCM. In this study, we retrospectively investigated the association between QT dispersion and sudden cardiac death in 46 patients with HCM (mean 33.1 ±; 15.5 years, 32 men). The case group consisted of 23 HCM patients who died suddenly, and the control group consisted of 23 HCM patients who survived uneventfully during follow‐up. Study patients were pair‐matched for age, gender, and maximum left ventricular wall thickness. QT dispersion (maximum minus minimum QT interval) was manually measured on early 12‐lead ECGs using a digitizing; board. An in‐house program was used for calculating QT interval, QT dispersion, JT interval, and JT dispersion (maximum minus minimum J point to T end interval). Patients in the case group tended to have shorter RR intervals than those in the control group (777 ±; 171 vs 856 ±; 192 ms, P = 0.08). Maximum corrected QT and JT intervals did not discriminate the case group from controls (489 ±; 29 vs 479 ±; 27 ms, P = NS; 375 ±; 36 vs 366 ±; 22 ms, P = NS, respectively). Greater QT dispersion and JT dispersion were found in the case group compared with controls (74 ±; 28 vs 59 ±; 21 ms, P = 0.02 and 76 ±; 32 vs 59 ±; 26 ms, P = 0.03, respectively). The measurements of maximum QT, JT, and T peak to T end intervals, precordial QT and JT dispersion, and T peak and T end dispersion were all comparable between the two groups (P = NS for all). No systematic changes in ECG measurements were found from late ECGs of the case group compared to those from early ECGs (P = NS). No correlation between maximum left ventricular wall thickness and QT dispersion, JT dispersion, maximum QTc or JTc intervals was observed (r < 0.29, P > 0.05 for all). Our results; show that increased QT dispersion and JT dispersion is weakly associated with sudden cardiac death in the selected patients with HCM. A.N.E. 2001; 6(3):209–215
Heart Block in Dextrocardia and Situs Inversus:
Authors: Brito Mitermayer R. , Miranda Carlos E. , Barros Vladimir C. , Castro Luiz R. , Borges Maria H.
Published: October 2006

The authors report a case of a 39‐year‐old woman with dextrocardia and situs inversus who presented with episodes of complete heart block, managed successfully with a permanent dual chamber endocardial pacemaker. A.N.E. 2001;6(4):369–372
Relationship Between Changes in R‐wave Amplitude During Left Ventriculography and the Seriousness of Coronary Heart Disease
Authors: Erdöl Cevdet , Baykan Merih , Çelik Şükrü , Gökçe Mustafa , Karahan Burhan , Örem Cihan
Published: October 2006

Serious complications, such as myocardial infarction or death, may occur particularly in patients with severe coronary heart disease during coronary angiographies. Therefore, prediction of severe coronary heart disease before or during the initial steps of the procedure can provide a decrease in frequency of such complications. To predict the seriousness of coronary heart disease during left ventriculography, before, during, and after the application of contrast matter, electrocardiography (ECG) records were taken and R‐wave amplitudes were measured. Lead Oil was used for calculations. The patients were classified according to vessel lesions and were compared with the control group. Before and after left ventriculography, there was no significant difference between the groups with normal coronary arteries and one, two, or three vessel lesions. Although there was no significant difference obtained from the comparison of the control group and the groups with one‐vessel and two‐vessel lesions (9.7 mm, 9.2 mm, 10.1 mm, respectively, P > 0.05); there was statistical difference between the group with three‐vessel lesions and the control group during left ventriculography i6.4 mm, 9.7 mm, respectively, P < 0.05). Nonionic contrast material was used in all procedures. The decrement of R‐wave amplitude that is observed during left ventriculography can predict three‐vessel disease, which is a more serious condition for the patients. These patients should be monitored more carefully during coronary angiographies. A.N.E. 2002;7(2):114–119
P‐Wave Signal‐Averaged Electrocardiogram Predicts Atrial Fibrillation After Coronary Artery Bypass Grafting
Authors: Caravelli Paolo , De Carlo Marco , Musumeci Giuseppe , Tartarini Giuseppe , Gherarducci Gherardo , Bortolotti Uberto , Mariani Massimo A. , Mario Mariani And
Published: October 2006

Background: AF is one of the most common complications after CABG. The aim of the study was to identify the risk factors for postoperative AF.

Methods: Between June and December 2000, 129 consecutive patients (72 men, 47 women; mean age 67 ± 6 years) underwent preoperative signal‐averaged electrocardiogram (SAECG) with assessment of filtered P‐wave duration (fPWD) and of the root mean square voltage of the last 10 and 20 ms of atrial depolarization (RMSV10 and RMSV20, respectively) before CABG.

Results: Fifty‐six (43%) patients developed one episode of AF lasting > 30 seconds at a mean distance of 2.6 ± 1.8 days after surgery (group A), while 73 patients remained in sinus rhythm (group B). No differences between the two groups were found in terms of age, sex, P‐wave duration on the standard ECG, left atrial dimensions, and operative characteristics. In contrast, group A patients showed a significantly longer fPWD (138 ± 10 vs 111 ± 9 ms; P < 0.001) and smaller RMSV10 and RMSV20 (2.8 ± 1.0 vs 4.3 ± 1.1 μV, P < 0.001; 4.2 ± 2.1 vs 6.2 ± 2.0 μV, P < 0.001). Multivariate analysis indicated only fPWD as an independent predictor of AF (P = 0.009). With a cut‐off value of 135 ms for fPWD, the occurrence of AF could be predicted with a sensitivity of 84%, a specificity of 73%, a negative predictive value of 85%, and a positive predictive value of 70%.

Conclusion: Preoperative SAECG is a simple exam that correctly identifies patients at higher risk of AF after CABG. A more widespread use of this technique can be suggested. A.N.E. 2002;7(3):198–203
Cardiovascular Autonomic Function in Conscious Rats: A Novel Approach to Facilitate Stationary Conditions
Authors: Ramaekers Dirk , Beckers Frank , Demeulemeester Hilde , Aubert André E.
Published: October 2006

Background An experimental setting and software were developed to evaluate cardiovascular autonomic function in conscious rats. A restrained approach was used, which, upon proper habituation, induced little or no stress in the rats and limited motion artifacts.

Methods: The ECG and arterial blood pressure were recorded. Time‐ and frequency‐domain indices of heart rate variability (HRV) and blood pressure variability (BPV) were calculated. The spontaneous baroreflex sensitivity (spBRS) was estimated using the method of statistical dependence.

Results: The power spectra clearly concentrated in a frequency band with center frequency around 0.4 Hz, the low frequency (LF) component, and one at the respiratory frequency at 1.5 Hz, the high frequency (HF) component. In baseline conditions, a direct association existed between mean R‐R and especially HRV parameters denoting vagal modulation such as rMSSD, pNN5, and HF power. Beta‐adrenergic blockade by propranolol diminished basal heart rate. Vagal indices increased while there was an exclusive decrease in the low frequency band of HRV. Alpha‐adrenergic blockade with phentolamine produced a depressor response with tachycardia, and a clear decrease in the LF component of BPV. Both the LF and HF component in the HRV spectrum were virtually absent. Cholinergic blockade with atropine did not significantly alter BP but induced a clear tachycardia with decreased vagal indices. The HF component of HRV was completely abolished and the LF band was reduced.

Conclusions: Both a‐ and 13‐adrenergic blockade left 5pBRS virtually unaltered, while cholinergic blockade profoundly diminished spBRS. Spectral fluctuations of 13‐sympathetic tone were restricted to the LF range of HRV, while the HF respiratory component represented vagal modulation. The a‐sympathetic system played a dominant role in the LF oscillations of BPV. A role of the vagus in the HF oscillations of BPV in the rat is questioned. The baroreflex depended mainly on changes in vagal activity. A.N.E. 2002;7(4):307–318