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  • 1
    Electronic Resource
    Electronic Resource
    Circadian Modulation of Atrial Cycle Length in Human Chronic Permanent Atrial Fibrillation: A Noninvasive Assessment Using Long-Term Surface ECG (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 5 (2000), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objectives: Short-term autonomic influences on the electrophysiological properties (EP) of the atrial myocardium are well known, but the role of long-term sympathovagal influences on EP is less clear. This study aimed at finding if a circadian pattern could be identified in atrial EP, using the fibrillatory wave (F wave) of surface ECG recordings as a surrogate of atrial refractoriness in patients with chronic permanent atrial fibrillation (AFib).Methods: 24-hour two-channel Holter ECG were obtained in 20 consecutive patients (mean age 70 ± 8 years) with nonvalvular, chronic and permanent AFib, free of antiarrhythmic agents except digoxin. Digitized ECG were analyzed by a custom software. After QRST substraction of detected complexes, the residual F waves (5-min duration) were computed by a Fourier algorithm. The dominant frequency peak of the power spectrum obtained has been shown to correspond to the dominant atrial cycle length (DACL). 24-hour recordings were analyzed separately during the day (8 active and awake consecutive hours) and at night (4 resting and asleep consecutive hours), and DACL was calculated hourly for each diurnal and nocturnal periods.Results: Spectra could be reliably studied in 17 patients (85%). The DACL showed a significant circadian pattern with a mean 3.3% increase, from 151 ms in the diurnal period to 156 ms at night (P 〈 0.001). A significant positive relation was found between circadian day-night changes of DACL and the baseline DACL value (P 〈 0.05). Mean ventricular heart rate decreased from 87 beats/min during the diurnal period to 71 beats/min at night (P 〈 0.001).Conclusion: Spectral analysis of the F wave can be successfully achieved from long-term Holter recordings. In chronic permanent AFib, the DACL still shows a circadian rhythmicity with an increase from day to night. In addition to atrial refractoriness, the amplitude of DACL circadian modulation could represent a new index of atrial electrical remodeling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2000.tb00398.x
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative Aspects of Ventricular Repolarization (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 2 (1997), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: QT dispersion assesses repolarization inhomogeneity on 12-lead standard ECG. However, the implications of the electrical cardiac vector during the repolarization phase (the T wave loop) with the genesis of this phenomenon are unknown.Methods and Results: The aim of this study was to explore conventional 12-lead resting ECG QT dispersion and the corresponding morphology of the spatial three-dimensional (3-D) T wave loop in 25 normals subjects, 30 postmyocardial infarction (Ml) patients, and in 17 individuals with congenital long QT syndrome (LQTS). Standard and XYZ ECG leads were simultaneously digitized (250 Hz) and automatically analyzed. Ventricular repolarization dispersion was estimated by the range (RAN12o) and standard deviation (SD12o) of the 12 rate corrected QTo intervals (between the Q wave onset and the T wave offset). Spatial T wave loops were extracted from XYZ data and analyzed with a 3-D algorithm which provides quantitative parameters related to the loop morphology. All scalar measurements of dispersion were significantly larger in the two pathological populations; however none of them could discriminate post-MI from LQTS groups (RAN12o = 33.3, 61.4, and 62.7 ms respectively, for the three populations). Conversely, a loss of planarity and an increased roundness of the T wave loop were observed in the two pathological groups, with the former effect more pronounced in the LQTS (P = 0.04 compared to post-MI) and the latter in the post-MI group (P = 0.02 compared to LQTS). Furthermore, multiple regression and principal component analyses showed that planarity and roundness are independently involved with QT dispersion.Conclusion: Changes in the morphology of the spatial T wave loop associated with QT dispersion were identified. These changes discriminate different substrates of repolarization inhomogeneity. The use of a 3-D technique to assess repolarization inhomogeneity may bring additional information on the intrinsic nature of this disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1997.tb00322.x
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  • 3
    Electronic Resource
    Electronic Resource
    Death Due to an Implantable Cardioverter Defibrillator (2004)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 15 (2004), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Inappropriate therapy due to noise oversensing caused a true ventricular fibrillation (VF) and death of a patient. A 49-year-old patient with a history of dilated cardiomyopathy received a double-chamber implantable cardioverter defibrillator (ICD) in 1991 for a sustained inducible ventricular tachycardia (VT). One appropriate shock delivered in 1994 terminated an episode of VT. The generator was replaced in 1995 and in 2000, and was connected to the initial leads. Three months after the second replacement, the patient received six consecutive shocks related to detection of noise interpreted as VF. Unfortunately, the sixth shock triggered a true VF, which was not treated due to end of the therapeutic sequence, and the patient died. The causes of the dysfunction are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.03611.x
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  • 4
    Electronic Resource
    Electronic Resource
    High-Flow Perfusion of Sheaths for Prevention of Thromboembolic Complications During Complex Catheter Ablation in the Left Atrium (2004)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 15 (2004), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Mechanisms for thromboembolic complications during complex ablation procedures in left atrium (LA) have not been defined. The aim of this study was to determine the effect of the perfusion rate of the transseptal sheath on the incidence of thromboembolic complications during catheter ablation for atrial fibrillation (AF) or LA macroreentrant tachycardia. Methods and Results: We analyzed clinical and procedural data from 86 consecutive patients (153 procedures) referred for catheter ablation of AF (74 patients) or LA macroreentrant tachycardia (12 patients). The transseptal sheath was continuously perfused at a low flow rate (3 mL/hour) for the first 32 patients and at a high flow rate (180 mL/hour) for the subsequent 54 patients. Ablation was mainly performed using map-guided isolation of pulmonary veins for AF and three-dimensional electroanatomic mapping for LA macroreentrant tachycardia. Five patients (6% of patients and 3.5% of procedures) developed a cerebral thromboembolic complication, all during procedures using low-flow perfusion. Sheath perfusion rate and total procedure duration were the two variables significantly associated with the occurrence of stroke (P = 0.013 and 0.001, respectively). After adjustment in a multivariable analysis, sheath perfusion rate remained the only risk factor for stroke. The risk was 17 times higher using low-flow than high-flow perfusion (odds ratio 17.26, 95% confidence interval 1.14–260.81, P = 0.04). No other clinical or procedural parameters had any significant effect. Conclusion: Sheath perfusion rate is an important determinant of the risk factor for stroke during complex LA ablation procedures. Continuous high-flow perfusion appears to be effective in preventing this complication. (J Cardiovasc Electrophysiol, Vol. 15, pp. 276-283, March 2004)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.03401.x
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  • 5
    Electronic Resource
    Electronic Resource
    Diagnostic Performance of a Dual-Chamber Cardioverter Defibrillator Programmed with Nominal Settings: A European Prospective Study (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 13 (2002), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Arrhythmia Discrimination by ICD. Introduction: Despite technologic developments, accurate discrimination of ventricular tachyarrhythmia from rapid rhythms of nonventricular origin remains a challenge. We sought to examine the sensitivity and specificity of a dual-chamber arrhythmia detection algorithm, the PARAD algorithm, incorporated in a dual-chamber implantable cardioverter defibrillator, the Defender (ELA Medical). Methods and Results:All detailed tachycardia episodes (i.e., with stored atrial and ventricular channel markers and electrograms) retrieved from the Holter memory of the device were analyzed from 95 patients (86 men and 9 women; age 62 ± 12 years) implanted with the Defender with the algorithm programmed at nominal settings. Over a follow-up of 15 ± 8 months, 559 detailed sustained tachycardia episodes detected in the tachycardia zone were gathered in 62 patients. Of the 300 ventricular tachycardia (VT) episodes, 298 were appropriately classified as VT by the algorithm. Of the 259 supraventricular tachycardia (SVT) episodes, 231 were appropriately classified as SVT. In 8 patients, 28 episodes of SVT were misclassified as VT: 25 atrial fibrillation episodes (6 patients), 2 sinus tachycardia (1 patient), and 1 atrial tachycardia. Calculated sensitivity and specificity were 99.3% and 89.2% on a per episode basis and 99.8% (95% confidence interval: 97.8 to 100) and 91.6% (95% confidence interval: 86.0 to 97.3) on a per patient basis, respectively. Conclusion: In this selected population of patients, the PARAD algorithm was safe and reliable for detection of a wide spectrum of tachyarrhythmias. Its specificity was high, particularly with respect to sinus tachycardia detection, but it must be improved with respect to detection of atrial fibrillation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2002.00025.x
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  • 6
    Electronic Resource
    Electronic Resource
    Cardiac Effects of Chronic Oral Beta-Blockade: (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 7 (2002), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Although well established on the sinus node, the effects of beta-blockade on ventricular repolarization are still conflicting. The aim of the study was to investigate the effects of a chronic beta-blockade on sinus node and repolarization parameters and their relationship.Methods: Sixteen healthy volunteers (10 males, mean age: 40 ± 6.7 years) were randomized to placebo or atenolol (100 mg). After 7 days, subjects were crossed over. Heart rate (HR) and HRV indices were calculated from long-term ECG recordings separately during the day and at night, together with ventricular repolarization parameters (QT interval duration and QT rate-dependence).Results: Mean R-R intervals were significantly and consistently increased after atenolol (Day: 916 ± 103 ms vs. 712 ± 89 ms, and Night: 1149 ± 93 vs. 996 ± 125 ms). HRV changes under atenolol were also consistent, with a significant decrease in sympathovagal ratio. In contrast, atenolol only lowered diurnal QT rate-dependence (0.123 ± 0.032 vs. 0.190 ± 0.065 on placebo, P 〈 0.001), but not the nocturnal pattern. After multivariate analysis QT rate-dependence changes induced by atenolol were correlated with pretreatment QT/RR relation (r = 0.65, P 〈 0.01) but not with any HR or HRV parameters.Conclusions: In healthy subjects, repolarization changes following chronic beta-blockade cannot be predicted by HR or HRV changes, but are dependent on pretreatment rate-dependence. A.N.E. 2002;7(4):379–388
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2002.tb00189.x
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  • 7
    Electronic Resource
    Electronic Resource
    Individual QT–R-R Relationship: Average Stability over Time Does Not Rule Out an Individual Residual Variability: Implication for the Assessment of Drug Effect on the QT Interval (2005)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Publishing, Inc.
    Annals of noninvasive electrocardiology 10 (2005), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Universal QT correction formulae have been shown to under or overcorrect the QT interval duration. Individual QT–R-R modeling has been proposed as a preferable solution for heart rate correction of QT intervals. However, the QT–R-R relationship stability over time needs to be evaluated. Methods: The present report is part of randomized, double-dummy, and placebo-controlled 4-way crossover phase 1 study (48 healthy volunteers). Each randomized period included a run-in placebo day followed the day after by drug administration, with moxifloxacin as a positive control for QT interval measurement. Digital Holter ECG data were analyzed using the “bin” approach. For each period, individual QT–R-R relationship were calculated using two different models (linear and parabolic log–log models). Results: The mean intrasubject variability for the α coefficient of the linear modeling (SDintra = 0.011 ± 0.005) reached 28.6 ± 10.2%. When the parabolic model was considered, the SDintra was 0.026 ± 0.009 for the α coefficient. The QT–R-R relationship variability was in part related to long-term RR changes (R2= 30%, P 〈 0.05). However, no significant time effect (ANOVA) was evidenced for QT–R-R coefficients. Moxifloxacin significantly increased the α coefficient of the QT–R-R relationship from 0.07 ± 0.018 to 0.085 ± 0.019, P 〈 0.05 (linear model). Conclusions: The individual QT–R-R relationship shows a residual variability in part related to long-term autonomic changes. In addition, the QT–R-R relationship might be modulated by the drug tested. As a consequence, pretherapy QT–R-R relationship obtained in a given patient cannot be used as a fingerprint throughout a drug trial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.2005.05615.x
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  • 8
    Electronic Resource
    Electronic Resource
    Study of Precursors of Ventricular Tachycardia from Data Stored in the Memory of a Dual Chamber Implantable Cardioverter Defibrillator (2003)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This study was performed to examine precursors of ventricular tachyarrhythmias in patients who experienced a sustained ventricular tachyarrhythmia and received appropriate therapy by ICD. From an overall consecutive population of 77 patients, 18 patients (1 woman, mean age 61.7 ± 10.8 years ) were selected for having experienced a sustained ventricular tachyarrhythmia and received at least one appropriate ICD therapy preceded by 20 minutes of internal information. The number of premature ventricular complexes (PVCs)/min for each of the 20 minutes preceding the onset of ventricular tachyarrhythmia, the shortest coupling intervals between PVC and normal sinus beat, and the presence of short-long-short (SLS) interval sequences were examined. Data were stratified according to underlying disease, left ventricular ejection fraction, rate of ventricular tachyarrhythmia, and antiarrhythmic therapy. One hundred twenty-eight episodes of spontaneous ventricular tachyarrhythmia were retrieved. Rapid ventricular tachyarrhythmia (〉160 beats/min) were preceded by a significantly greater mean number (3.71 ± 6.36) of PVCs than slower ventricular tachyarrhythmia (≤160 beats/min) (0.63 ± 0.88, P = 0.0004) . The mean shortest PVC coupling interval was significantly shorter in patients with (588 ± 99 ms) versus without (643 ± 111 ms, P = 0.03) ischemic heart disease, before episodes of rapid (527 ± 55 ms) versus slower (636 ± 105 ms, P = 0.0001) ventricular tachyarrhythmia, and in the absence (538 ± 80 ms) versus the presence (620 ± 105 ms, P = 0.006) of amiodarone. SLS sequences preceded 29% of rapid ventricular tachyarrhythmic episodes, versus 8% of the slower ventricular tachyarrhythmia (P 〈 0.01) . Significant differences were found in the characteristics of PVCs preceding ventricular tachyarrhythmic episodes in accordance to their rate and the underlying cardiomyopathy. Though insufficient in isolation, these findings may be helpful when combined with other observations to develop preventive algorithms, or to refine the programming of implantable devices. (PACE 2003; 26[Pt. I]:1454–1460)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2003.t01-1-00210.x
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  • 9
    Electronic Resource
    Electronic Resource
    Preliminary Clinical Experience with the First Dual Chamber Pacemaker Defibrillator (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 20 (1997), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The lack of specificity of VT detection is a significant shortcoming of current ICDs. In a French multicenter study, 18 patients underwent implantation of the Defender 9001 (ELA Medical), an ICD utilizing dual chamber pacing and arrhythmia detection. Over a mean follow-up period of 7.1 ± 4.5 months, 176 tachycardia episodes recorded in the device memory were analyzed, and physician diagnosis was compared with that by the device. All 122 VT/VF episodes were correctly diagnosed, as were 51 of 53 supraventricular tachyarrhythmias. Two episodes of AF with rapid regular ventricular rates were treated as VT, and a third episode, treated as VT, could not be diagnosed with certainty. A dual chamber pacemaker defibrillator offers improved diagnostic specificity without loss of sensitivity, in addition to the hemodynamic benefit of dual chamber pacing. (PACE 1997;20
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1997.tb04839.x
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  • 10
    Electronic Resource
    Electronic Resource
    An Unusual Mode of Initiation of Supraventricular Tachycardia (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb00800.x
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