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  • 1
    Electronic Resource
    Electronic Resource
    Supraventricular Tachycardia with 2:1 Atrioventricular Block: What is the Mechanism? (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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.00386.x
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  • 2
    Electronic Resource
    Electronic Resource
    Electrogram Polarity and Cavotricuspid Isthmus Block During Ablation of Typical Atrial Flutter (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: Electrogram Polarity in Atrial Flutter Ablation. Introduction: The atrial activation sequence around the tricuspid annulus has been used to assess whether complete block has been achieved across the cavotricuspid isthmus during radiofrequency ablation of typical atrial flutter. However, sometimes the atrial activation sequence does not clearly establish the presence or absence of complete block. The purpose of this study was to determine whether a change in the polarity of atrial electrograms recorded near the ablation line is an accurate indicator of complete isthmus block. Methods and Results: Radiofrequency ablation was performed in 34 men and 10 women (age 60 ± 13 years [mean ± SD]) with isthmus-dependent, counterclockwise atrial flutter. Electrograms were recorded around the tricuspid annulus using a duodecapolar halo catheter. Electrograms recorded from two distal electrode pairs (E1 and E2) positioned just anterior to the ablation line were analyzed during atrial flutter and during coronary sinus pacing, before and after ablation. Complete isthmus block was verified by the presence of widely split double electrograms along the entire ablation line. Complete bidirectional isthmus block was achieved in 39 (89%) of 44 patients. Before ablation, the initial polarity of E1 and E2 was predominantly negative during atrial flutter and predominantly positive during coronary sinus pacing. During incomplete isthmus block, the electrogram polarity became reversed either only at E2, or at neither E1 nor E2. In every patient, the polarity of E1 and E2 became negative during coronary sinus pacing only after complete isthmus block was achieved. In 4 patients (10%), the atrial activation sequence recorded with the halo catheter was consistent with complete isthmus block, but the presence of incomplete block was accurately detected by inspection of the polarity of E1 and E2. Conclusion: Reversal of polarity in bipolar electrograms recorded just anterior to the line of isthmus block during coronary sinus pacing after ablation of atrial flutter is a simple, quick, and accurate indicator of complete isthmus block.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.00393.x
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  • 3
    Electronic Resource
    Electronic Resource
    Wide QRS Complex Tachycardia in a Patient with Wolff-Parkinson-White Syndrome and Cardiomyopathy: What is the Mechanism? (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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2000.tb01767.x
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  • 4
    Electronic Resource
    Electronic Resource
    Relationship Between Serum Potassium Concentration and Risk of Recurrent Ventricular Tachycardia or Ventricular Fibrillation (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: Serum Potassium and Defibrillator Shocks. Introduction: Electrolyte abnormalities are considered a correctable cause of a life-threatening ventricular arrhythmia according to American Heart Association/American College of Cardiology Practice Guidelines, and ventricular tachycardia or ventricular fibrillation in the setting of an electrolyte abnormality is considered a class III indication for defibrillator implantation. However, there are little data to support this recommendation. The purpose of this study was to determine the risk of a recurrent sustained ventricular arrhythmia in patients with a low serum potassium concentration at the time of an initial episode of a sustained ventricular arrhythmia. Methods and Results: One hundred sixty-nine consecutive patients who presented with a sustained ventricular arrhythmia and a serum potassium concentration determined on the day of the arrhythmia underwent defibrillator implantation. All patients had structural heart disease and left ventricular ejection fraction of 0.32 ± 0.15. On the day of the index arrhythmia, 30% of the patients had a serum potassium concentration 〈 3.5 or 〉 5.0 mEq/L, including 7% who had a serum potassium concentration 〈 3.0 or 〉 6.0 mEq/L. For the entire cohort of patients, freedom from a recurrent sustained ventricular arrhythmia was 18% at 5 years and was not significantly different among patients with a serum potassium concentration 〈 3.5 mEq/L (23%), between 3.5 and 5.0 mEq/L (16%), and 〉 5.0 mEq/L (5%; P = 0.1). Conclusion: The results of the present study suggest that patients with structural heart disease and an abnormal serum potassium concentration at the time of an initial episode of sustained ventricular tachycardia or ventricular fibrillation are at high risk for a recurrent ventricular arrhythmia; therefore, implantable defibrillator therapy may be reasonable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2001.01109.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of the Implantable Atrial Defibrillator on the Natural History of Atrial Fibrillation (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
    Notes: Implantable Atrial Defibrillator. Introduction: The purpose of our study was to evaluate the effect of repeated cardioversion with an implantable atrial defibrillator on the clinical outcome of patients with atrial fibrillation. Methods and Results: The effects of the implantable atrial defibrillator on the total duration of atrial fibrillation, number of atrial fibrillation recurrences, and left atrial size were evaluated prospectively in 16 patients with atrial fibrillation (13 men and 3 women; mean age 58 ± 11 years). Seven patients bad no cardiovascular disease, 5 patients had hypertension. 3 patients had coronary heart disease, and 1 patient bad congenital heart disease. Eight patients had paroxysmal atrial fibrillation for a mean duration of 80 ± 61 months, and eight patients had persistent atrial fibrillation for a mean duration of 68 ± 119 months. Except for one patient who received digoxin throughout the study, alt patients received the same Class I or III antiarrhythmic agent throughout the study. The implantable atrial defibrillator successfully converted 50 (93%) of 54 spontaneous episodes of atrial fibrillation in 12 patients. During the initial 3 months of clinical follow-up, the atrial defibrillator documented 261 ± 270 hours of atrial fibrillation compared with 126 ± 172 hours (P = 0.01) during the subsequent 3 months. The left atrial size decreased from 4.4 ± 0.7 cm at the time of atrial defibrillator implantation to 4.1 ± 0.6 cm (P = 0.02) 6 months later. The number of atrial fibrillation recurrences did not change. These findings were observed in the absence of changes in drug therapy. No complications were observed. Conclusion: Restoration and maintenance of sinus rhythm in patients with atrial fibrillation by repeated cardioversion with an implantable atrial defibrillator was associated with a reduction in the total arrhythmia duration and a reduction in left atrial size. These results suggest that maintenance of sinus rhythm with the atrial defibrillator may reverse the remodeling process associated with atrial fibrillation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00296.x
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of Endocardial Activation Times at Effective and Ineffective Ablation Sites Within the Pulmonary Veins (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: Pulmonary Vein Arrhythmias. Introduction: Recent studies demonstrated that atrial arrhythmias may be generated within pulmonary veins. The purpose of this study was to compare the endocardial activation times at effective and ineffective ablation sites during radiofrequency catheter ablation of arrhythmias initiated or generated within pulmonary veins. Methods and Results: Twenty-one of 28 patients without structural heart disease underwent successful ablation of 23 arrhythmogenic foci within a pulmonary vein. Electrograms were recorded at 75 pulmonary venous sites and categorized into three groups: 23 successful ablation sites; 28 unsuccessful target sites within an arrhythmogenic pulmonary vein; and 24 sites within nonarrhythmogenic pulmonary veins. The endocardial activation time of premature depolarizations arising at successful target sites was significantly earlier than at other sites. During premature depolarizations, an endocardial activation time of -75 msec or earlier had a sensitivity of 83% and a specificity of 79% for identification of a successful ablation site. Endocardial activation times earlier than -100 msec were recorded only at successful ablation sites, and endocardial activation times later than -30 msec were recorded only at sites within nonarrhythmogenic pulmonary veins. The presence of a split potential during sinus rhythm or premature depolarizations was not a specific indicator of a successful ablation site. Conclusion: The endocardial activation times of premature depolarizations that arise within pulmonary veins and initiate atrial tachycardia/fibrillation are useful in identifying successful ablation sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2000.tb00314.x
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  • 8
    Electronic Resource
    Electronic Resource
    Discrete Systolic Potentials During Ventricular Tachycardia in Patients with Prior Myocardial Infarction (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
    Notes: Systolic Potentials, introduction: Isolated diastolic potentials have been found to be helpful in identifying critical sites for ablation of ventricular tachycardia (VT) in patients with coronary artery disease. However, discrete potentials that occur during systole have not been previously described. The purpose of this study was to determine the significance of discrete systolic potentials during VT in patients with coronary artery disease. Methods and Results: Twenty-seven patients with a mean age of 66 ± 12 years (± standard deviation) who bad coronary artery disease underwent radiofrequency catheter ablation of 42 VTs that had a mean cycle length of 486 ± 78 msec. The only criterion used to select target sites for ablation was concealed entrainment, which was present at 92 sites. Thirty-five of the 42 VTs (83%) were successfully ablated. A discrete systolic potential was recorded during 7 of the 42 VTs (17%). In all cases, the interval between the discrete systolic potential and the next QRS complex was equal to the stimulus-QRS interval during concealed entrainment. At all seven sites where a discrete systolic potential was recorded, delivery of radiofrequency energy resulted in successful ablation of the VT. Conclusion: Discrete systolic potentials may be present in patients with coronary artery disease in approximately 17% of VTs in which there is concealed entrainment. If the interval between the discrete systolic potential and the next QRS complex matches the stimulus-QRS interval during concealed entrainment, delivery of radiofrequency energy is likely to result in successful ablation of the VT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00684.x
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  • 9
    Electronic Resource
    Electronic Resource
    Target Temperatures of 48°C versus 60°C During Slow Pathway Ablation: (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
    Notes: Slow Pathway Ablation. Introduction: The relationship between temperature at the electrode-tissue interface and the loss of AV and ventriculoatrial (VA) conduction is not established, and the optimal target temperature for the slow pathway approach to radiofrequency ablation of AV nodal reentrant tachycardia (AVNRT) is unknown. Therefore, the purpose of this study was to compare target temperatures of 48°C and 60°C during the slow pathway approach to ablation of AVNRT. Methods and Results: The study included 138 patients undergoing ablation for AVNRT. Patients undergoing slow pathway ablation using closed-loop temperature monitoring were randomly assigned to a target temperature of either 48°C or 60°C. The primary success rates were 76% in the patients assigned to 48°C and 100% in the patients assigned to 60°C (P 〈 0.01). The ablation procedure duration (33 ± 31 min vs 26 ± 28 min; P = 0.2), fluoroscopic time (25 ± 15 min vs 24 ± 16 min; P = 0.5), and mean number of applications (9.3 ± 6.5 vs 7.8 ± 8.1; P = 0.3) were similar in patients assigned to 48° and 60°C, respectively. The mean temperature (46.1°± 24.8°C vs 48.7°± 3.2°C; P 〈 0.01), the temperature associated with junctional ectopy (48.1°± 2.0°C vs 53.5°± 3.5°C, P 〈 0.0001), and the frequency of VA block during junctional ectopy (24.6% vs 37.2%; P 〈 0.0001) were less in the patients assigned to 48°C compared to 60°C. The frequency of transient or permanent AV block was similar in each group (2.8% vs 3.6%; P = 0.2). In the 60°C group, only 12% of applications achieved an electrode temperature of 60°C. During follow-up of 9.9 ± 4.2 months, there was one recurrence of AVNRT in the 48°C group and none in the 60°C group. Conclusions: Compared to 48°C, a target temperature of 60°C during radiofrequency slow pathway ablation is associated with a higher primary success rate and a higher incidence of VA block during junctional ectopy induced by the radiofrequency energy. AV block is not more common with the higher target temperature, but only if VA conduction is aggressively monitored during applications of radiofrequency energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00259.x
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  • 10
    Electronic Resource
    Electronic Resource
    Correlation Waveform Analysis to Discriminate Monomorphic Ventricular Tachycardia from Sinus Rhythm Using Stored Electrograms from Implantable Defibrillators (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: In order to examine whether a template-matching program utilizing correlation waveform analysis (CWA) might be used to discriminate monomorphic ventricular tachycardia (MMVT) from sinus rhythm (SR) in patients with implantable cardioverter defibrillators (ICDs), we studied stored episodes of induced MMVT in 25 patients and compared them to corresponding stored SR electrograms. We calculated mean correlation coefficients for SR beats against an SR template chosen within each sinus episode, induced MMVT beats against an induced MMVT template within each ventricular tachycardia episode, and induced MMVT beats against the original SR template. For each patient, the 99.5% lower confidence limit for the mean correlation coefficient of SR beats versus an SR template (patient-specific method) or the empirical correlation coefficient value 0.9 were selected as threshold values to discriminate induced MMVT from SR. The mean correlation coefficient for induced MMVT beats versus the original SR template for each patient was subtracted from both threshold values. A positive value is defined as accurate discrimination of induced MMVT from SR. Using 0.9 for a threshold cut off, 21 of 25 episodes of induced MMVT were accurately labeled with a sensitivity of 84%. Using the patient-specific method, we were able to correctly distinguish 23 of 25 episodes of induced MMVT from SR with a sensitivity of 92%. There was no statistically significant difference between the patient-specific or empirical methods in detecting MMVT (P 5 0.4). This is the first demonstration using stored intracardiac electrograms from ICDs that CWA is able to discriminate MMVT from SR with high sensitivity. Such a template-matching system may be used for off-line analysis or real-time rhythm discrimination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1999.tb00593.x
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