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  • 1
    Electronic Resource
    Electronic Resource
    Electrocardiographic Markers of Late Sudden Death Risk in Postoperative Tetralogy of Fallot Children (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
    Notes: Late Sudden Death Risk in Postoperative TOF. Following surgery for tetralogy of Fallot (TOP), children may develop late onset ventricular arrhythmias. Many patients have both depolarization and repolarization abnormalities, including right bundle branch block (RBBB) and QT prolongation. The goal of this study was to improve prospective risk-assessment screening for late onset sudden death. Resting ECG markers including QRS duration, QTc, JTc, and interlead QT and JT dispersion were statistically analyzed to identify those patients at risk for ventricular arrhythmias and sudden cardiac death. To determine predictive markers for future development of arrhythmia, we examined 101 resting ECGs in patients (age 12 ± 6 years) with postoperative TOF and RBBB, 14 of whom developed late ventricular tachycardia (VT) or sudden death. These ECGs were also compared with an additional control group of 1000 age- and gender-matched normal ECGs. The mean QRS (± SD) in the VT group was 0.18 ± 0.02 seconds versus 0.14 ± 0.02 seconds in the non-VT group (P 〈 0.01). QTc and JTc in the VT group was 0.53 ± 0.05 seconds and 0.33 ± 0.03 seconds compared with 0.50 ± 0.03 seconds and 0.32 ± 0.03 seconds in the non-VT group (P = NS). There was no increase in QT dispersion among TOF patients with VT or sudden death compared with control patients or TOF patients without VT, although JT dispersion was more common in the TOF groups. A prolonged QRS duration in postoperative TOF with RBBB is more predictive than QTc, JTc, or dispersion indexes for identifying vulnerability to ventricular arrhythmias in this population, while retaining high specificity. The combination of both QRS prolongation and increased JT dispersion had very good positive and negative predictive values. These results suggest that arrhythmogenesis in children following TOF surgery might involve depolarization in addition to repolarization abnormalities. Prospective identification of high-risk children may be accomplished using these ECG criteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb01031.x
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  • 2
    Electronic Resource
    Electronic Resource
    Minimally Invasive Cardioverter Defibrillator Implantation for Children: An Animal Model and Pediatric Case Report (2001)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 24 (2001), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: BERUL, C.I., et al.: Minimally Invasive Cardioverter Defibrillator Implantation for Children: An Animal Model and Pediatric Case Report. The smaller venous capacitance in infants and small children may hamper transvenous ICD lead implantation, and epicardial approaches require thoracotomy and have associated complications. The study evaluated the feasibility and performance of subcutaneous arrays and active can ICDs without transvenous shocking coils or epicardial patches. An immature and mature pig were anesthetized and ventilated. A pacing lead was inserted in the right ventricle for fibrillation induction and rate sensing. Subcutaneous arrays were positioned in the right and left chest walls. An ICD emulator was placed in abdominal and prepectoral pockets. Fluoroscopic images were acquired for each electrical vector configuration (array → can, can → array, array → array, array + array → can). Ventricular fibrillation was induced and DFT testing performed. Defibrillation was achieved in all ten trials in the immature piglet, with DFT ≤ 9 J, regardless of vector configuration. Using a single subcutaneous array and active can, the shock impedance ranged from 28–36 ohms. With two arrays, shocking impedance fell to 15–22 ohms. In the adult pig, defibrillation was not accomplished with maximum energy of 40 J, using all vector configurations. Using data garnered from these experiments, this technique was then successfully performed in a 2-year-old child with VT and repaired congenital heart disease, needing an ICD. This study demonstrates the feasibility of leadless ICD implantation in an immature animal and successful implementation in a small child. A single subcutaneous array and active can resulted in excellent implant characteristics and DFTs with a minimally invasive approach. Defibrillation was not possible in a larger animal, possibly due to maximal available energy. This may be of value for small children requiring ICD implantation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.01789.x
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  • 3
    Electronic Resource
    Electronic Resource
    An Interesting Case of Infant Sudden Death: Severe Hypertrophic Cardiomyopathy in Pompe's Disease (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 22 (1999), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Glycogen storage disease type II (Pompe's disease) is a rare inherited metabolic disorder, which often leads to infantile death from severe cardiomyopathy. This case of sudden death illustrates the features of the cardiac findings in the disorder, resulting from massive lysosomal accumulation of glycogen in the heart and other tissues. Pompe's disease should be considered in cases of unexplained infantile cardiomyopathy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00551.x
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  • 4
    Electronic Resource
    Electronic Resource
    Transcoronary Ethanol Ablation of the Atrioventricular Node in a Young Patient with Tricuspid Atresia (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Catheter ablation of AV conduction with radiofrequency energy can be challenging in the presence of structural abnormalities of the AV junction, either congenitally or after reconstructive surgery. We used transcoronary ethanol to ablate the AV node in a patient with classic tricuspid atresia and refractory intraatrial reentry tachycardia. This approach provides an alternative means of creating complete heart block with catheter-based techniques, when radiofrequency catheter ablation is technically impossible or ineffective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb00108.x
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  • 5
    Electronic Resource
    Electronic Resource
    QT and JT Dispersion in Children with Long QT Syndrome (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
    Notes: QT and JT Dispersion in Long QT Syndrome. Introduction: Abnormalities of ventricular repolarization leading to ventricular arrhythmias place children with long QT syndrome at high risk for sudden death. Dispersion of the QT (QTd) and JT (JTd) intervals, as markers of cardiac electrical heterogeneity, may be helpful in evaluating children with long QT syndrome and identifying a subset of patients at high risk for development of critical ventricular arrhythmias (ventricular tachycardia, torsades de pointes, and/or cardiac arrest).Methods and Results: The QTd and JTd intervals in 39 children with long QT syndrome were compared to those of 50 normal age-matched children. In the long QT syndrome group, QTd measured 81 ± 70 msec compared to 28 ± 14 msec in the control group (P 〈 0.05), and JTd in the long QT syndrome group was 80 ± 69 msec compared to 25 ± 15 msec in the control group (P 〈 0.05).Conclusion: Children with long QT syndrome have an increased QTd and JTd when compared to normal controls. A QTd or JTd ≥ 55 msec correlates with the presence of critical ventricular arrhythmias. These ECG measures of dispersion can be useful in stratifying children with the long QT syndrome who are at higher risk for developing critical ventricular arrhythmias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb01827.x
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  • 6
    Electronic Resource
    Electronic Resource
    Implantable Cardioverter Defibrillator Lead Complications and Laser Extraction in Children and Young Adults with Congenital Heart Disease: Implications for Implantation and Management (2003)
    350 Main Street , Malden , MA 02148 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 14 (2003), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Implantable cardioverter defibrillators (ICDs) are being implanted for primary and secondary prevention of sudden death in children and young adults with congenital heart disease. Over time, ICD leads adhere to venous endothelium and endocardium. Lead removal, when necessary, often requires disruption of this fibrous tissue. Methods and Results: We retrospectively reviewed and analyzed our experience with ICD lead extraction in children and young adults with congenital heart disease. From April 1999 through January 2002, 14 patients underwent 15 lead extraction procedures to remove 21 leads (17 ICD leads and 4 pacing or sensing leads). Seven patients had surgically corrected structural heart disease (5 transposition of the great arteries with atrial switch repair and 2 corrected tetralogy of Fallot). Mean patient age at extraction was 17.9 ± 5.7 years (range 9–32), and mean duration of lead implantation was 42.0 ± 18.9 months (range 15–75). Fourteen of 15 procedures were performed for lead fracture or failure. A laser sheath was used for 20 of 21 lead extractions. Twenty of 21 leads (95%) were completely extracted. There were three instances of blood loss requiring transfusion. There were no major complications or deaths. Conclusion: Young congenital heart disease patients with an ICD are at risk for growth-related lead distortion. The use of a laser sheath is safe and effective for ICD lead extraction in congenital heart disease patients, despite coil adherence and altered anatomy. It may be advisable to avoid dual-coil leads in patients with the potential for future growth. (J Cardiovasc Electrophysiol, Vol. 14, pp. 344-349, April 2003)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2003.02500.x
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  • 7
    Electronic Resource
    Electronic Resource
    In Vivo Electrophysiologic Studies in Endothelial Nitric Oxide Synthase (eNOS)-Deficient Mice (2001)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 12 (2001), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Electrophysiologic Studies in eNOS-Deficient Mice. Introduction: Endothelial nitric oxide synthase (eNOS) mediates attenuation of the L-type calcium channel and modulates myocyte contractility. Arrhythmogenic afterdepolarizations are seen in vitro in ouabain-treated isolated myocytes from eNOSdeficient mice. The aim of these studies was to characterize the baseline electrophysiologic (EP) phenotype of eNOS-deficient mice and their potential susceptibility to cardiac conduction abnormalities and inducible arrhythmias. Methods and Results: Surface ECG and in vivo intracardiac EP studies were performed in 27 mice lacking the eNOS gene and 21 wild-type littermate control mice. Baseline studies were performed in 10 eNOS-deficient mice and 10 wild-type controls. Subsequently, 17 eNOS-deficient mice and 11 wild-type controls were pretreated with digoxin, and ECG and EP testing were repeated. Data analysis revealed no significant differences in ECG intervals or cardiac conduction parameters, except sinus cycle length was higher in eNOS-deficient mice than wild-type mice (P 〈 0.01). After digoxin pretreatment, 7 of 17 eNOS-deficient mice had inducible ventricular tachycardia and 2 others had frequent ventricular premature beats, compared with only 3 of 11 wild-type mice with inducible ventricular tachycardia. In addition, 2 digoxin-treated eNOS-deficient mice and 1 wild-type mouse had inducible nonsustained atrial fibrillation. Conclusion: Mice with a homozygous targeted disruption of the eNOS gene have slower heart rates but no other distinguishable EP characteristics under basal sedated conditions. Partial inhibition of the Na+/K+ ATPase pump with digoxin administration increases ventricular ectopic activity in eNOS–/– mice, a phenotype analogous to afterdepolarizations seen in vitro in this eNOS-deficient mouse model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.01295.x
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  • 8
    Electronic Resource
    Electronic Resource
    Maturational Atrioventricular Nodal Physiology in the Mouse (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Mouse AV Nodal Maturation. Introduction: Dual AV nodal physiology is characterized by discontinuous conduction from the atrium to His bundle during programmed atrial extrastimulus testing (A2V2 conduction curves), AV nodal echo beats, and induction of AV nodal reentry tachycardia (AVNRT). The purpose of this study was to characterize in vivo murine maturational AV nodal conduction properties and determine the frequency of dual AV nodal physiology and inducible AVNRT. Methods and Results: A complete transvenous in vivo electrophysiologic study was performed on 30 immature and 19 mature mice. Assessment of AV nodal conduction included (1) surface ECG and intracardiac atrial and ventricular electrograms; (2) decremental atrial pacing to the point of Wenckebach block and 2:1 conduction; and (3) programmed premature atrial extrastimuli to determine AV effective refractory periods (AVERP), construct A2V2 conduction curves, and attempt arrhythmia induction. The mean Wenckebach block interval was 73 ± 12 msec, 2:1 block pacing cycle length was 61 ± 11 msec, and mean AVERP100 was 54 ± 11 msec. The frequency of dual AV nodal physiology increased with chronologic age, with discontinuous A2V2, conduction curves or AV nodal echo heats in 27% of young mice 〈 8 weeks and 58% in adult mice (P = 0.03). Conclusion: These data suggest that mice, similar to humans, have maturation of AV nodal physiology, hut they do not have inducible AVNRT. Characterization of murine electrophysiology may be of value in studying genetically modified animals with AV conduction abnormalities. Furthermore, extrapolation to humans may help explain the relative rarity of AVNRT in the younger pediatric population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2000.tb00009.x
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  • 9
    Electronic Resource
    Electronic Resource
    A Gap in Understanding the Connection Between Connexins and Cardiac Conduction (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 10 (1999), 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.1540-8167.1999.tb00193.x
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  • 10
    Electronic Resource
    Electronic Resource
    A Comparison of T-Wave Alternans and QT Dispersion as Noninvasive Predictors of Ventricular Arrhythmias (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 4 (1999), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:The purpose of this study was to compare the utility of T-wave alternans and dispersion markers for predicting vulnerability to ventricular arrhythmias. Microvolt level T-wave alternans, QT dispersion (QTd), JT dispersion, and other dispersion indices have been postulated as noninvasive markers of vulnerability to ventricular arrhythmias. However, T-wave alternans has not been directly compared to dispersion markers in the same patient population. Methods:Twenty-four patients underwent electrophysiological study to investigate recent syncope, ventricular tachycardia, or ventricular fibrillation. Digitized orthogonal ECGs were obtained to investigate the presence of T-wave alternans using spectral analysis, and standard 12-lead ECGs were obtained for QT and JT dispersion analysis. Results:T-wave alternans measurements showed greater sensitivity than QT or JT dispersion, but similar results as the variation coefficient of the JT interval. There was no statistically significant difference in specificity, predictive values, or clinical accuracy between T-wave alternans and any of the dispersion markers (P = N.S.). The combination of increased QT or JT dispersion and T-wave alternans was the most specific predictor. Conclusions:Heterogeneity of repolarization amplitude and duration may both be important noninvasive ECG markers of ventricular vulnerability. In this small group of high-risk patients, T-wave alternans has similar clinical accuracy as the ECG interlead repolarization dispersion markers. The predictive ability of these markers may improve with standardization of methodology or a combination of these approaches. A.N.E. 1999;4(3):274–280
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1999.tb00211.x
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