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Backgrounds: Radiofrequency (RF) catheter ablation represents a major advance in the management of children with cardiac arrhythmias and has rapidly become the standard of care for the first-ling therapy of supraventricular tachycardias (SVTs). The purpose of this study was to investigate the results of the RF catheter ablation of SVTs in pediatric patients. Methods: From December 1989 to August 2005, a total of 228 pediatric patients (age: 9 ± 7 years, range: 5–18 years; male:female = 117:111) with clinically documented SVT underwent an electrophysiologic study and RF catheter ablation at our institution. Results: The arrhythmias included atrioventricular reentrant tachycardia (AVRT; n = 140, 61%), atrioventricular nodal reentrant tachycardia (AVNRT; n = 66, 29%), atrial tachycardia (AT; n = 11, 5%), and atrial flutter (AFL; n = 11, 5%). The success rate of the RF catheter ablation was 92% for AVRT, 97% for AVNRT, 82% for AT, and 91% for AFL, respectively. Procedure-related complications were infrequent (8.7%; major complications: high grade AV block (2/231, 0.9%); minor complications: first degree AV block (6/231, 2.6%), reversible brachial plexus injury (2/231, 0.9%), and local hematomas or bruises (10/231, 4.3%)). The recurrence rate was 4.7% (10/212) during a follow-up period of 86 ± 38 months (0.5–185 months). Conclusions: The RF catheter ablation was a safe and effective method to manage children with paroxysmal and incessant tachycardia. The substrates of the arrhythmias differed between the pediatric and adult patients. However, the success rate of the ablation, complications, and recurrence during childhood were similar to those of adults. [ABSTRACT FROM AUTHOR]

Background: Atrioventricular nodal reentrant tachycardia (AVNRT) can usually be induced by atrial stimulation. However, it seldom may be induced with only ventricular stimulation, especially the fast-slow form of AVNRT. The purpose of this retrospective study was to investigate the specific electrophysiological characteristics in patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation. Methods: The total population consisted of 1,497 patients associated with AVNRT, and 106 (8.4%) of them had the fast-slow form of AVNRT and 1,373 (91.7%) the slow-fast form of AVNRT. In patients with the fast-slow form of AVNRT, the AVNRT could be induced with only ventricular stimulation in 16 patients, Group 1; with only atrial stimulation or both atrial and ventricular stimulation in 90 patients, Group 2; and with only atrial stimulation in 13 patients, Group 3. We also divided these patients with slow-fast form AVNRT (n = 1,373) into two groups: those that could be induced only by ventricular stimulation (Group 4; n = 45, 3%) and those that could be induced by atrial stimulation only or by both atrial and ventricular stimulation (n = 1.328, 97%). Results: Patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation had a lower incidence of an antegrade dual AVN physiology (0% vs 71.1% and 92%, P < 0.001), a lower incidence of multiple form AVNRT (31% vs 69% and 85%, P = 0.009), and a more significant retrograde functional refractory period (FRP) difference (99 ± 102 vs 30 ± 57 ms, P < 0.001) than those that could be induced with only atrial stimulation or both atrial and ventricular stimulation. The occurrence of tachycardia stimulated with only ventricular stimulation was more frequently demonstrated in patients with the fast-slow form of AVNRT than in those with the slow-fast form of AVNRT (15% vs 3%, P < 0.001). Patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation had a higher incidence of retrograde dual AVN physiology (75% vs 4%, P < 0.001), a longer pacing cycle length of retrograde 1:1 fast and slow pathway conduction (475 ± 63 ms vs 366 ± 64 ms, P < 0.001; 449 ± 138 ms vs 370 ± 85 ms, P = 0.009), a longer retrograde effective refractory period of the fast pathway (360 ± 124 ms vs 285 ± 62 ms, P = 0.003), and a longer retrograde FRP of the fast and slow pathway (428 ± 85 ms vs 362 ± 47 ms, P < 0.001 and 522 ± 106 vs 456 ± 97 ms, P = 0.026) than those with the slow-fast form of AVNRT that could be induced with only ventricular stimulation. Conclusion: This study demonstrated that patients with the fast-slow form of AVNRT that could be induced with only ventricular stimulation had a different incidence of the antegrade and retrograde dual AVN physiology and the specific electrophysiological characteristics. The mechanism of the AVNRT stimulated only with ventricular stimulation was supposed to be different in patients with the slow-fast and fast-slow forms of AVNRT. [ABSTRACT FROM AUTHOR]

Background: Previous studies in adults have shown a significant shortening of the fast pathway effective refractory period (ERP) after successful slow pathway ablation. However, information on atrioventricular nodal reentrant tachycardia (AVNRT) in children is limited. The purpose of this retrospective study was to investigate the different effects of radiofrequency (RF) catheter ablation in pediatric AVNRT patients between those with and without dual atrioventricular (AV) nodal pathways. Methods: From January 1992 to August 2004, a total 67 pediatric patients with AVNRT underwent an electrophysiologic study and RF catheter ablation at our institution. We compared the electrophysiologic characteristics between those obtained before and after ablation in the children with AVNRT with and without dual AV nodal pathways. Results: Dual AV nodal pathways were found in 37 (55%) of 67 children, including 36 (54%) with antegrade and 10 (15%) with retrograde dual AV nodal pathways. The antegrade and retrograde fast pathway ERPs in children with dual AV nodal pathways were both longer than the antegrade and retrograde ERPs in children without dual AV nodal pathways (300 ± 68 vs 264 ± 58 ms, P = 0.004; 415 ± 70 vs 250 ± 45 ms, P < 0.001) before ablation. In children with antegrade dual AV nodal pathways, the antegrade fast pathway ERP decreased from 300 ± 68 ms to 258 ± 62 ms (P = 0.008). The retrograde fast pathway ERP also decreased after successful ablation in the children with retrograde dual AV nodal pathways (415 ± 70 vs. 358 ± 72 ms, P = 0.026). Conclusion: The dual AV nodal physiology could not be commonly demonstrated in pediatric patients with inducible AVNRT. After a successful slow pathway ablation, the fast pathway ERP shortened significantly in the children with dual AV nodal pathways. [ABSTRACT FROM AUTHOR]

Background: The majority of cardiac arrhythmias in children are supraventricular tachycardia, which is mainly related to an accessory pathway (AP)-mediated reentry mechanism. The investigation for Wolff-Parkinson-White (WPW) syndrome in adults is numerous, but there is only limited information for children. This study was designed to evaluate the specific electrophysiologic characteristics and the outcome of radiofrequency (RF) catheter ablation in children with WPW syndrome. Methods: From December 1989 to August 2005, a total of 142 children and 1,219 adults with atrioventricular reentrant tachycardia (AVRT) who underwent ablation at our institution were included. We compared the clinical and electrophysiologic characteristics between children and adults with WPW syndrome. Results: The incidence of intermittent WPW syndrome was higher in children (7% vs 3%, P= 0.025). There was a higher occurrence of rapid atrial pacing needed to induce tachycardia in children (67% vs 53%, P= 0.02). However, atrial fibrillation (AF) occurred more commonly in adult patients (28% vs 16%, P = 0.003). The pediatric patients had a higher incidence of multiple pathways (5% vs 1%, P < 0.001). Both the onset and duration of symptoms were significantly shorter in the pediatric patients. The antegrade 1:1 AP conduction pacing cycle length (CL) and antegrade AP effective refractory period (ERP) in children were much shorter than those in adults with manifest WPW syndrome. Furthermore, the retrograde 1:1 AP conduction pacing CL and retrograde AP ERP in children were also shorter than those in adults. The antegrade 1:1 atrioventricular (AV) node conduction pacing CL, AV nodal ERP, and the CL of the tachycardia were all shorter in the pediatric patients. Conclusion: This study demonstrated the difference in the electrophysiologic characteristics of APs and the AV node between pediatric and adult patients. RF catheter ablation was a safe and effective method to manage children with WPW syndrome. [ABSTRACT FROM AUTHOR]

LEE, S-H.,et al.: Electrophysiological Characteristics of Junctional Rhythm During Ablation of the Slow Pathway in Different Types of Atrioventricular Nodal Reentrant Tachycardia. Background:Junctional rhythm (JR) is commonly observed during radiofrequency (RF) ablation of the slow pathway for atrioventricular (AV) nodal reentrant tachycardia. However, the atrial activation pattern and conduction time from the His-bundle region to the atria recorded during JR in different types of AV nodal reentrant tachycardia have not been fully defined.Methods:Forty-five patients who underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia were included; 27 patients with slow-fast, 11 patients with slow-intermediate, and 7 patients with fast-slow AV nodal reentrant tachycardia. The atrial activation pattern and HA interval (from the His-bundle potential to the atrial recording of the high right atrial catheter) during AV nodal reentrant tachycardia (HASVT) and JR (HAJR) were analyzed.Results:In all patients with slow-fast AV nodal reentrant tachycardia, the atrial activation sequence recorded during JR was similar to that of the retrograde fast pathway, and transient retrograde conduction block during JR was found in 1 (4%) patient. The HAJR was significantly shorter than the HASVT (57± 24 vs 68± 21 ms, P<0.01). In patients with slow-intermediate AV nodal reentrant tachycardia, the atrial activation sequence of the JR was similar to that of the retrograde fast pathway in 5 (45%), and to that of the retrograde intermediate pathway in 6 (55%) patients. Transient retrograde conduction block during JR was noted in 1 (9%) patient. The HAJR was also significantly shorter than the HASVT (145± 27 vs 168± 29 ms, P= 0.014). In patients with fast-slow AV nodal reentrant tachycardia, retrograde conduction with block during JR was noted in 7 (100%) patients. The incidence of retrograde conduction block during JR was higher in fast-slow AV nodal reentrant tachycardia than slow-fast (7/7 vs 1/11, P<0.01) and slow-intermediate AV nodal reentrant tachycardia (7/7 vs 1/27, P<0.01).Conclusions:In patients with slow-fast and slow-intermediate AV nodal reentrant tachycardia, the JR during ablation of the slow pathway conducted to the atria through the fast or intermediate pathway. In patients with fast-slow AV nodal reentrant tachycardia, there was no retrograde conduction during JR. These findings suggested there were different characteristics of the JR during slow-pathway ablation of different types of AV nodal reentrant tachycardia.(PACE 2005; 28:111–118) [ABSTRACT FROM AUTHOR]

LIN, Y.-J.,et al.: Electrophysiological Mechanisms and Catheter Ablation of Complex Atrial Arrhythmias from Crista Terminalis: Insight from Three-Dimensional Noncontact Mapping. Paroxysmal atrial fibrillation (PAF) can be initiated by ectopic activation from the crista terminalis. The crista terminalis conduction gap is also a critical isthmus in atrial reentrant arrhythmias like upper and lower loop reentry. The aim of this study was to investigate the mechanism and results of catheter ablation for complex atrial arrhythmias originating from the crista terminalis using the noncontact mapping system (NCM). The study population consisted of six patients (5 men, 1 woman; 70± 9 years) with drug refractory PAF and typical/atypical atrial flutter. NCM identified the earliest ectopic activation originating from the crista terminalis in these six patients. The reentry circuit of atypical atrial flutter propagated around the upper crista terminalis in five patients, and lower crista terminalis in one patient. The reentry circuit of atypical atrial flutter and the initial reentry circuit of AF conducted through the crista terminalis gap in all patients. Radiofrequency applications were delivered on the sites of ectopy, which initiated AF. Substrate modification was also performed over the crista terminalis gap (six patients) and cavotricuspid isthmus (three patients) responsible for the reentry. During a mean follow-up of 9± 5 months (range 5–18 months), five patients were free of AF without antiarrhythmic drugs, and one patient did not have AF or atrial flutter using propafenone. NCM demonstrated the mechanism of crista terminalis ectopy-initiating AF and associated typical/atypical atrial flutter. Catheter ablation of crista terminalis ectopy and substrate for the reentry guided by NCM successfully eliminated these atrial arrhythmias.(PACE 2004; 27:1231–1239) [ABSTRACT FROM AUTHOR]

LEE, P.-C., et al.: The Different Electrophysiological Characteristics in Children with Wolff-Parkinson-White Syndrome Between Those with and Without Atrial Fibrillation. Atrioventricular reciprocating tachycardia (AVRT) is known to be the most common supraventricular tachycardias in childhood. Because AF with rapid ventricular response may degenerate to ventricular fibrillation through conduction of accessory pathways (APs), it can be potentially life-threatening in some pediatric patients with WPW syndrome. However, information about WPW syndrome children associated with AF is limited. The purpose of this study was to investigate the specific electrophysiological characteristics in pediatric patients with WPW syndrome and AF. From July 1992 to February 2002, 51 pediatric patients with manifest WPW syndrome and documented AVRT underwent electrophysiological study and radiofrequency catheter ablation. In these patients, two (4%) were found to have several spontaneous episodes of AF recognized on 12-lead standard ECG or 24-hour Holter monitoring. Eleven (22%) patients had AF induced by rapid atrial pacing during the baseline procedure of electrophysiological study. The children with manifest WPW syndrome were divided into two groups: those with AF (group 1; n = 11) consisted of seven male and four female children (mean age 15 ± 3 years, range 10–18), and those without AF (group 2; n = 40) consisted of 22 boys and 18 girls (mean age 16 ± 3 years, range 7–18). The study excluded a patient who had Ebstein's anomaly associated with moderate tricuspid regurgitation and right atrial enlargement. The onset and duration of symptoms were not significantly different between the two groups. Comparing the electrophysiological characteristics, the atrial effective refractory period (ERP) was shorter in WPW syndrome children with AF (170 ± 36 vs 190 ± 38 ms, P = 0.041). This study demonstrated that the pediatric WPW syndrome patients with AF had different electrophysiological characteristics from those without AF. (PACE 2004; 27:235–239) [ABSTRACT FROM AUTHOR]

LEE, P.-C., et al.: Effects of a Blocked Atrial Beat on the Atrioventricular Nodal Recovery Property in Patients with Dual Nodal Pathways. Dual AVN physiology can be demonstrated by a variety of maneuvers. To determine whether AVN recovery times following a blocked extrastimulus facilitate or obscure detection of dual AVN physiology, 11 patients (9–17 years) were studied with dual AVN pathways by using single and double atrial extrastimuli. With a single atrial extrastimuli, the premature atrial stimulus (A2) was coupled to basic atrial beats (A1). The fast and slow AVN recovery curves were constructed with plots of the nodal conduction time against the recovery time (A1A2,A2H2). With double atrial extrastimuli, a fixed blocked A2 beat (A2B) was followed by a scanning atrial beat (A3). The nodal recovery property post-A2B was studied by plots of A2BA3,A3H3. In all patients the recovery curve of the fast pathway post-A2B had a leftward shift when compared to that of the pre-A2B curve (i.e., the AH was shortened at the same recovery time). The window of slow pathway conduction post-A2B disappeared totally in five patients and decreased significatly in six patients (post-A2B: 26 ± 42 ms; pre-A2B: 80 ± 65 ms, P < 0.05). In the six patients that still had slow pathway conduction post-A2B, the slow pathway effective refractory period post-A2B was significantly less than that of pre-A2B (215 ± 38 vs 268 ± 16 ms, P < 0.05). The fast pathway effective refractory period post-A2B was also diminished significantly (235 ± 62 vs 357 ± 76 ms, P < 0.0001). The authors conclude that blocked atrial beats decrease the visibility of the slow pathway conduction. (PACE 2003; 26:2091–2095) [ABSTRACT FROM AUTHOR]

We report a case with dextrocardia, corrected transposition of the great arteries. He also had an atrial septum defect (ASD) with patch repair. Activation map showed a centrifugal activation from a focal origin on the systemic lower left atrial ASD patch. Ablation of the origin can terminate the atrial tachycardia. (PACE 2012; 35:e306-e308) [ABSTRACT FROM AUTHOR]

Presents the case of a 15-year-old man with a supraventricular tachycardia with changing morphology of QRS complex and tachycardia cycle length induced by ventricular burst pacing. Medical history of the patient; Possible mechanism explaining supraventricular tachycardias with progressive change of QRS complex morphology; Reason for the progressive preexcitation of the QRS complex.