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  • 1
    Electronic Resource
    Electronic Resource
    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 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Atrial arrhythmias often complicate congestive heart failure (CHF). We characterized inducible atrial tachyarrhythmias and electrophysiologic alterations in dogs with CHF and atrial enlargement produced by rapid ventricular pacing. Methods and Results: Endocardial pacing leads were implanted in the right ventricle, right atrium, and coronary sinus in 18 dogs. The right ventricular lead was connected to an implanted pacemaker capable of rapid ventricular pacing. The atrial leads were used to perform electrophysiologic studies in conscious animals at baseline in all dogs, during CHF induced by rapid ventricular pacing at 235 beats/min in 15 dogs, and during recovery from CHF in 6 dogs. After 20 ± 7 days of rapid ventricular pacing, inducibility of sustained atrial tachycardia (cycle length 120 ± 12 msec ) was enhanced in dogs with CHF. Atrial tachycardia required a critical decrease in atrial burst pacing cycle length (≤130 msec) for induction and often could be terminated by overdrive pacing. Calcium antagonists (verapamil, flunarizine, ryanodine) terminated atrial tachycardia and suppressed inducibility. Effective refractory periods at 400- and 300-msec cycle lengths in the right atrium and coronary sinus were prolonged in dogs with CHF. Atrial cells from dogs with CHF had prolonged action potential durations and reduced resting potentials and delayed afterdepolarizations (DADs). Mitochondria from atrial tissue from dogs with CHF were enlarged and had internal cristae disorganization. Conclusions: CHF promotes inducibility of sustained atrial tachycardia. Based on the mode of tachycardia induction, responses to pacing and calcium antagonists, and presence of DADs, atrial tachycardia in this CHF model has a mechanism most consistent with DAD-induced triggered activity resulting from intracellular calcium overload. (J Cardiovasc Electrophysiol, Vol. 14, pp. 499-507, May 2003)
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 23 (2000), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Permanent biatrial and/or multisite atrial pacing may prevent atrial fibrillation (AF), but the effects on atrial electrophysiology remain incompletely understood. Acute biatrial pacing was studied in 20 patients with and 28 without (controls) a history of atrial fibrillation and/or flutter. Twelve-lead electrocardiograms were recorded during pacing from the high right atrium (RA), from the distal coronary sinus (LA), and biatrial pacing. P wave duration was measured in each lead and the difference between maximum and minimum P duration was termed P wave dispersion. Effective refractory periods (ERPs) were measured during each pacing mode. The dispersion of P wave duration was 35 ± 14 ms in controls and 40 ± 29 ms in AF patients (P = 0.17). Compared to RA pacing, LA pacing shortened P duration in controls (127 ± 18 to 107 ± 16 ms, P 〈 0.05) and biatrial pacing markedly shortened P duration in controls (127 ± 18 to 93 ± 14 ms, P 〈 0.05) and AF patients (114 ±43 to 97 ± 21 ms, P 〈 0.05). P wave dispersion was unaffected. In controls, the LA ERP was longer than the RA ERP. This phenomenon was not present in AF patients, whose LA ERP was shorter than that of controls. Biatrial pacing had no effect on atrial ERPs or the dispersion of atrial refractoriness. In conclusion, acute biatrial pacing does not affect atrial repolarization but it does cause a marked shortening of global biatrial depolarization. Distal coronary sinus pacing produces a shorter P wave than RA pacing. There is substantial dispersion in the surface P wave of the electrocardiogram, the significance of which awaits further study.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 7 (1996), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: ANP and Cardiac Electrophysiology. Atrial natriuretic peptide (ANP) has varied effects on cardiac electrophysiologic parameters including heart rate, intraatrial conduction time, and refractory period. ANP's vagoexcitatory and sympathoinhibitory actions as well as its direct actions on cardiac ion currents may be responsible for some of these effects. This review discusses the role of ANP in cardiac electrophysiology, its interactions with the autonomic nervous system and baroreceptor reflex, and its effects on cardiac ion currents.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    350 Main Street , Malden , MA 02148-5018 , U.S.A . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: GILLIGAN, D.M., et al .: Long-Term Outcome of Patients After Successful Radiofrequency Ablation for Typical Atrial Flutter. The aim of the study was to determine the long-term freedom from atrial arrhythmias after radiofrequency ablation of atrial flutter and to determine the factors associated with recurrent arrhythmias. Radiofrequency ablation has emerged as the preferred treatment for recurrent, typical atrial flutter. Although the short-term results after radiofrequency ablation of atrial flutter have been widely reported, there is insufficient data on long-term outcome with respect to the occurrence of atrial arrhythmias in patients after successful ablation. The first 108 patients to undergo successful ablation for typical atrial flutter at the authors' institutions were followed prospectively until the occurrence of typical atrial flutter, atrial fibrillation, atypical atrial flutter, or death. Several prespecified clinical and procedural factors were tested using univariate and multivariate analysis as predictors of arrhythmia recurrence. Patients were followed for a minimum of 3 years and a maximum of 8 years, or until the first arrhythmia recurrence (average duration 17 ± 17 months). Recurrences of typical atrial flutter were usually observed within the first 6 months (73%, n = 16), with the remainder (27%, n = 6) occurring between 6 months and 2 years, and none were observed later. Freedom from recurrence of typical atrial flutter was 80% at 1 year (95% CIs 72–89%), 73% at 2 years (CIs 63–83%), and 73% at 5 years (CIs 63–83%). By contrast, freedom from occurrence of atrial fibrillation or atypical atrial flutter progressively declined over time; 80% at 1 year (CIs 71–88%), 59% at 2 years (CIs 48–70%), and 33% at 5 years (CIs 19–48%). A history of atrial fibrillation or atypical atrial flutter prior to ablation was associated with an increased risk of occurrence during follow-up (relative risk 3.4, CIs 1.5–8.1, P 〈 0.05). Freedom from occurrence of any atrial arrhythmia was only 27% at 5 years (CIs 15–40%). After successful ablation of typical atrial flutter, recurrence of typical flutter is relatively uncommon and usually occurs early. However, there is a progressive occurrence of atrial fibrillation and/or atypical flutter during follow-up so that many patients require further antiarrhythmic or additional ablative therapy. Radiofrequency ablation of typical atrial flutter should be considered a palliative procedure for most patients and only one component of the long-term care of the patient with atrial tachyarrhythmias. (PACE 2003; 26[Pt. I]:53–58)
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-8595
    Keywords: ventricular fibrillation ; monophasic action potential ; ventricular repolarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Introduction: Shocks given during the vulnerable period of cardiac repolarization may induce ventricular fibrillation (VF). However, the relationship of the vulnerable period and the monophasic action potential (MAP) has not yet been reported in humans. The purpose of this study was, therefore, to determine how the monophasic action potential recorded from the right ventricle correlates with inducibility of VF using T wave shocks during ventricular pacing. Methods: Eleven patients undergoing implantable cardioverter defibrillator (ICD) implantation had a MAP catheter positioned in the right ventricle (RV). The local monophasic action potential duration at 90% repolarization (MAP90) duration was measured during pacing at 400 ms. VF induction was attempted by pacing at 400 ms for 10 cycles and then giving a 1.0 joule monophasic T wave shock at varying coupling intervals (CI) to the last paced stimulus. The maximum and minimum CI that induced VF were determined and mapped in relation to the MAP90 recording. Results: The average paced MAP duration was 275 ± 20ms. The minimum and maximum CI to induce VF were 255 ± 24ms and 325 ± 36ms respectively. This ranged from 93% to 118% of the MAP90 duration but because of delay in conduction time to the MAP catheter, shocks that induced ventricular fibrillation occurred between 74% and 99% of local repolarization time. Conclusion: VF is inducible with low energy T wave shocks falling during the last 25% of the right ventricular MAP90 recording. This corresponds with VF initiation during phase III repolarization.
    Type of Medium: Electronic Resource
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