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Tachycardia Circuit (tachycardia + circuit)
Selected AbstractsShort Atrioventricular Mahaim Fibers: Observations on Their Clinical, Electrocardiographic, and Electrophysiologic ProfileJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2005EDUARDO BACK STERNICK M.D. Introduction: A short atrioventricular decrementally conducting accessory pathway is an uncommon variant of preexcitation. Available data from small series suggest that their decremental properties might not be caused by A-V nodal-like tissue. Methods: We compared clinical, electrocardiographic and electrophysiologic parameters in two groups of patients: 8 patients with a short A-V Mahaim pathway (Group A), and 33 patients with atriofascicular pathways (Group B). Radiofrequency catheter ablation was carried out guided by activation mapping at the annulus in Group A patients and targeting the "M" potential in Group B patients. Results: After ablation of all associated rapidly conducting bypass tracts, 7 of the 8 Group A patients showed clear preexcitation. In only 1 of 8 patients the short A-V Mahaim fiber was actively engaged in a reentrant tachycardia circuit. During radiofrequency catheter ablation an automatic rhythm occurred in 4 of 8 patients. Intravenous adenosine caused conduction a block in the Mahaim fiber in 3 of the 5 patients tested. In group B, no patient showed clear preexcitation (P < 00001) while 72% had a minimal preexcitation pattern. Twenty-nine of the 33 patients had a circus movement tachycardia with AV conduction over the atriofascicular fiber. During radiofrequency catheter ablation 30 of 33 patients showed accessory pathway automaticity. Adenosine caused transient block at the atriofascicular pathway in 11 (92%) of the 12 patients tested. Conclusions: While short decrementally conducting right-sided accessory pathways show a typical ECG pattern different from atriofascicular pathways, their electrophysiologic properties do not seem to be uniform. Those pathways can be successfully interrupted by catheter ablation. [source] Estimation of Entrainment Response Using Electrograms from Remote Sites: Validation in Animal and Computer Models of Reentrant TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2003PETER E. HAMMER M.S. Estimation of Entrainment Response. Introduction: Studies suggest that entrainment response (ER) of reentrant tachycardia to overdrive pacing can be estimated using signals from sites other than the paced site. Methods and Results: A formula for estimation of ER using remote sites against the difference between the postpacing interval (PPI) and tachycardia cycle length (TCL) determined solely from the paced site signal was validated in experimental data and using a simple two-dimensional cellular automata model of reentry. The model also was used to study the behavior and features of entrained surfaces, including the resetting of tachycardia phase by single premature paced stimuli. Experimental results from 1,484 remote sites in 115 pacing sequences showed the average of the median ER estimate error at each pacing site was,2 ± 5 msec, and the median ER estimate was within 10 msec of PPI,TCL for 94% of pacing sites. From simulation results, ER at the paced site was accurately estimated from >99.8% of 20,764 remote sites during pacing at 24 sites and three paced cycle lengths. Intervals measured from remote electrograms revealed whether the site was activated orthodromically or nonorthodromically during pacing, and results of simulations illustrated that the portion of the surface activated nonorthodromically during pacing increased with distance from the pacing site to the circuit. The phenomenon of nonorthodromic activation of reentrant circuits predicted by modeling was discernible in measurements taken from the animal model of reentrant tachycardia. Results also showed that, for single premature stimuli that penetrated the tachycardia circuit, phase reset of the tachycardia was linearly related to distance between the central obstacle and the paced site. Conclusion: The ER is a complex but predictable perturbation of the global activation sequence of reentrant tachycardias. This predictability allows calculations of the response from anywhere on the perturbed surface. These findings suggest new techniques for measurement of the ER, which may lend themselves to computer-based methods for accurate and rapid mapping of reentrant circuits. [source] Endocardial Noncontact Activation Mapping of Idiopathic Left Ventricular TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2000JASBIR SRA M.D. Mapping of Idiopathic Ventricular Tachycardia. Idiopathic left ventricular tachycardia with a right bundle, left-axis deviation is thought to originate from posterior fascicles. Recently, there has been considerable interest in the anatomic and mechanistic basis of this arrhythmia. We report our experience with a 26-year-old man in whom new noncontact mapping technology was used to acquire detailed data from the left ventricle, identify the mid-diastolic potential and part of the ventricular tachycardia circuit, and perform successful ablation. This information helped define the physiologic aspects of this unique tachycardia. [source] Reentry Within the Cavotricuspid Isthmus: An Isthmus Dependent CircuitPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2005YANFEI YANG Background: We describe a new cavotricuspid isthmus (CTI) circuit. Methods: This study includes 8 patients referred for atrial flutter (AFL) ablation whose tachycardia circuit was confined to the septal CTI and the os of the coronary sinus (CSOS) region. Entrainment mapping was performed within the CTI, CSOS, and other right atrial annular sites (tricuspid annulus (TA)). Electroanatomic mapping was available in 2 patients. Results: Sustained AFL occurred in all patients with mean tachycardia cycle length (TCL) of 318 ± 54 (276 , 420) ms. During tachycardia, fractionated or double potentials were recorded at either the septal CTI and/or the region of CSOS in all, and concealed entrainment with post-pacing interval (PPI) , TCL , 25 ms occurred in this area; but manifest entrainment with PPI > TCL was demonstrated from the anteroinferior CTI and other annular sites in 7/8 patients. In one, tachycardia continued with conduction block at the anteroinferior CTI during ablation. Up to three different right atrial activation patterns (identical TCL) were observed. The tachycardia showed a counterclockwise (CCW) pattern in 6, a clockwise pattern in 2, and simultaneous activation of both low lateral right atrium and septum in 5. Electroanatomic mapping was available in 2, showing an early area arising from the septal CTI in 1, and a CCW activation sequence along the TA in another. Radiofrequency application to the septal CTI terminated tachycardia in 4, and tachycardia no longer inducible in all. Conclusions: We describe a tachycardia circuit confined to the septal CTI/CSOS region, and hypothesize that this circuit involves slow conduction within the CTI and around the CSOS, which acts as a central obstacle. [source] Change in Morphology of Reentrant Atrial Arrhythmias Without Termination Following Radiofrequency Catheter AblationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2002MASAHIKO TAKAGI TAKAGI, M., et al.: Change in Morphology of Reentrant Atrial Arrhythmias Without Termination Following Radiofrequency Catheter Ablation. A 60-year-old woman who had previously undergone an atrial septal defect repair and had type I atrial flutter underwent electrophysiological study. After radiofrequency (RF) ablation to the isthmus between the inferior vena cava and the tricuspid annulus, type I atrial flutter was changed to atrial tachycardia following atriotomy without termination. This atrial tachycardia was eliminated by single-site RF ablation of a small lesion below the caudal end of the atriotomy scar, where continuous and fragmented potentials were recorded during tachycardia. We experienced a rare case in which RF energy changed tachycardia circuits. [source] | ||||||||||