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Reentrant Ventricular Tachycardia (reentrant + ventricular_tachycardia)
Selected AbstractsReentrant Ventricular Tachycardia Originating from the Aortic Sinus Cusp:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004A Case Report We report a case of idiopathic reentrant ventricular tachycardia (VT) originating from the left aortic sinus cusp. A prepotential preceding the QRS complex by 58 ms was recorded from the posterior right ventricular (RV) outflow tract. During VT entrainment observed by pacing from the midseptal RV, it initially was orthodromically captured with a long conduction time but then antidromically captured as the pacing cycle rate was increased. Pacing at that site failed to show concealed entrainment despite a postpacing interval similar to the VT cycle length. Radiofrequency catheter ablation abolished the VT in the left aortic sinus cusp where a prepotential preceding the QRS complex by 78 ms with a postpacing interval similar to the VT cycle length was recorded in addition to concealed entrainment. The findings suggest that, in this VT, a critical slow conduction zone is partially present extending from the left aortic sinus cusp to the posterior right ventricular outflow tract. The patient has remained free from VT recurrence after 5-month follow-up. [source] Role of Wavelength Adaptation in the Initiation, Maintenance, and Pharmacologic Suppression of ReentryJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2001STEVEN D. GIROUARD Ph.D. Wavelength Adaptation and Reentry.Introduction: The stability of reentry is thought to depend on a critical balance between the spatial extent of refractory tissue in a reentrant wave (i.e., wavelength ,) and the reentrant path length. Because considerable evidence suggests that , changes continuously in space and time during abrupt rate changes associated with the onset of tachycardia, we hypothesized that beat-by-beat adaptation of , to the dimensions of the reentrant path plays a central role in the mechanism of initiation of reentry. Methods and Results: To investigate the dynamic relationship between , and path length during initiation of reentry, optical mapping with voltage-sensitive dyes was used in a guinea pig model of reentrant ventricular tachycardia (VT). In this model, a computer-guided laser obstacle precisely controlled the position and dimensions of the reentrant path. Under control perfusion and after addition of 15 , M d-sotalol, , was monitored during steady-state pacing, premature stimulation, and the initiating beats leading to nonsustained and sustained VT. During control perfusion, reentrant VT was reproducibly induced in 8 of 8 hearts, whereas in the presence of d-sotalol, reentry could only be initiated in 1 of 8 hearts due primarily to the failure of , to adapt to the reentrant path length. During successful initiation of VT, a consistent sequence was observed. The sequence was characterized by antidromic and orthodromic propagation around both sides of the anatomic obstacle, followed by unidirectional block of the antidromic impulse and persistence of reentry only if the , of the orthodromic impulse adapted to the reentrant path (, < path length). d-Sotalol prevented initiation of VT by altering , adaptation of the orthodromic wave; however, it failed to terminate ongoing VT because reverse use-dependence developed after several beats of tachycardia. Conclusion: In an experimental model where ,, path length, and cellular action potentials were monitored during initiation of reentry, we found that, in contrast to termination, the initiation of reentry and the transition from nonsustained to sustained VT is strongly dependent on beat-to-beat adaptation of , to the dimensions of the reentrant path. [source] Relationship of Specific Electrogram Characteristics During Sinus Rhythm and Ventricular Pacing Determined by Adaptive Template Matching to the Location of Functional Reentrant Circuits that Cause Ventricular Tachycardia in the Infarcted Canine HeartJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2000EDWARD J. CIACCIO Ph.D. Localization of Reentrant Circuits. Introduction: It would be advantageous, for ablation therapy, to localize reentrant circuits causing ventricular tachycardia by quantifying electrograms obtained during sinus rhythm (SR) or ventricular pacing (VP). In this study, adaptive template matching (ATM) was used to localize reentrant circuits by measuring dynamic electrogram shape using SR and VP data. Methods and Results: Four days after coronary occlusion, reentrant ventricular tachycardia was induced in the epicardial border zone of canine hearts by programmed electrical stimulation. Activation maps of circuits were constructed using electrograms recorded from a multichannel array to ascertain block line location. Electrogram recordings obtained during SR/AP then were used for ATM analysis. A template electrogram was matched with electrograms on subsequent cycles by weighting amplitude, vertical shift, duration, and phase lag for optimal overlap. Sites of largest cycle-to-cycle variance in the optimal ATM weights were found to be adjacent to block lines bounding the central isthmus during reentry (mean 61.1% during SR; 63.9% during VP). The distance between the mean center of mass of the ten highest ATM variance peaks and the narrowest isthmus width was determined. For all VP data, the center of mass resided in the isthmus region ocurring during reentry. Conclusion: ATM high variance measured from SR/AP data localizes functional block lines forming during reentry. The center of mass of the high variance peaks localizes the narrowest width of the isthmus. Therefore, ATM methodology may guide ablation catheter position without resorting to reentry induction. [source] John B. Barlow: Master clinician and compleat cardiologistCLINICAL CARDIOLOGY, Issue 1 2000Tsung O. Cheng M.D. Abstract This paper reports the case of a 76-year-old man in whom atrial flutter with varying atrioventricular block and intermittent right bundle-branch block was found. This is the first report on tachycardia-dependent right bundle-branch block associated with supernormal conduction in a case of atrial flutter. When an impulse is conducted to the ventricles beyond 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse falls after the abnormally long effective refractory period of the right bundle branch and passes through the right bundle branch. When the conducted impulse occurs within 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse usually falls in the refractory period and is blocked in the right bundle branch; however, only when the impulse occurs 0.48 or 0.49 s after that does it fall in the supernormal period and passes through the right bundle branch. The findings in the present report strengthen our previous suggestion that the presence of supernormal conduction plays an important role in the initiation of reentrant ventricular tachycardia. [source] | ||||||||||