Jung-Yun Choi

Twin AV Node and Induced Supraventricular Tachycardia in Fontan Palliation Patients

Introduction: The coexistence of two distinct atrioventricular (AV) nodes has been described in congenital heart disease requiring Fontan type palliation. The purpose of this study was to evaluate the occurrence of twin AV node according to anatomical subgroups, and to determine its relation to tachycardia.

Pediatric Radiofrequency Catheter Ablation: Results of Initial 100 Consecutive Cases Including Congenital Heart Anomalies

Radiofrequency catheter ablation (RFCA) has recently become a management option for pediatric tachycardia. We reviewed the records of a total of 100 patients (aged 10 months to 19 yr) who had undergone RFCA, from March 2000 to June 2004. Types of arrhythmia (age, acute success rate) were as follows: atrioventricular reentrant tachycardia (AVRT, 9.0±3.7 yr, 66/67), atrioventricular nodal reentrant tachycardia (AVNRT, 13±2.5 yr, 16/16), ectopic atrial tachycardia (6.4±3.3 yr, 5/5), junctional ectopic tachycardia (10 month, 1/1), ventricular tachycardia (12±4.9 yr, 6/6), postsurgical intraatrial reentrant tachycardia (15.6±4.1 yr, 2/3), twin node tachycardia (4 yr, 0/1), and His bundle ablation (9 yr, 1/1). The age of AVNRT was older than that of AVRT (p=0.002). Associated cardiac disease was detected in 17 patients, including 6 univentricular patients, and 3 Ebsteins anomaly patients. RFCA for multiple accessory pathways required longer fluoroscopic times than did the single accessory pathway (53.9±4.8 vs. 36.2±24.1 min; p=0.03), and was associated with a higher recurrence rate (3/9 vs. 3/53; p=0.03). Regardless of the presence or absence of cardiac diseases, the overall acute success rate was 97% without major complications, the recurrence rate was 8.2%, and the final success rate was 97%. This experience confirmed the efficacy and safety of RFCA in the management of tachycardia in children.

Late Occurrence of Adenosine-Sensitive Focal Junctional Tachycardia in Complex Congenital Heart Disease

Background: Although supraventricular tachycardia in complex congenital heart disease (CHD) has been reported after surgical repair, its exact electrophysiologic identification has been limited to intraatrial reentrant tachycardia (IART). Moreover, junctional tachycardia (JT) has not previously been described as a cause of late postoperative arrhythmia.Methods and Results: Since 1993, a total of 12 patients with congenital heart disease presented with paroxysmal focal JT. The patients with only typical immediate postoperative junctional ectopic tachycardia were excluded. Medical records, standard electrocardiography and Holter monitoring were reviewed. An intracardiac electrophysiologic (EP) study was performed in 11 patients. Ten patients were in post-Fontan status (5.7% of total Fontan survivors). Focal JT occurred more frequently in heterotaxy syndrome among the Fontan survivors (7/52 vs. 3/124; P < 0.05). The commonest anatomy of the atrioventricular (AV) junction was complete AV canal in 8 patients. EP characteristics of focal JT were as follows: (1) various tachycardia mechanisms were identified (increased automaticity or a triggered mechanism in 6/11, and focal reentry in 5/11, including one concealed nodofascicular pathway) (2) ventriculoatrial conduction during tachycardia was either dissociation (7/12) or variable (5/12) (3) All JTs were terminated by adenosine. Class III antiarrhythmic agent was effective in 5/6. His bundle ablation was performed in one Fontan patient, who already had pacemaker because of accompanying intractable IART and sinus node dysfunction.Conclusion: Focal JT may be a source of late term supraventricular tachycardia in patients with complex CHD. The tachycardia mechanism was either automatic/triggered or reentrant. In all patients, JT was effectively terminated by adenosine.

Soft magnetic properties of nanocrystalline Fe‐Hf‐C‐N films

Fe‐Hf‐C‐N films with excellent soft magnetic properties were fabricated by Ar+N2 reactive sputtering for the first time. The newly developed films were found to have better soft magnetic properties than those of Fe‐Hf‐C or Fe‐Hf‐N films. The best magnetic properties achieved in this work are  Hc of 0.15 Oe, μeff of 8200, and 4πMs of 17 kG. The thermal stability of the Fe‐Hf‐C‐N films was also found to be excellent, e.g., Hc was less than 0.3 Oe and μeff was about 4000 for the films annealed up to 700 °C. It was observed by transmission electron microscopy that the films consisted of two phases: a fine crystalline α‐Fe phase whose grain size is about 6 nm, and Hf(C,N) precipitates with a size of less than 2 nm. The fine grained α‐Fe structures, together with finely dispersed Hf(C,N) precipitates, is considered to be one of the main factors for the excellent magnetic properties and thermal stability.

A Case of Congenital Junctional Ectopic Tachycardia: Prenatal Diagnosis and Successful Radiofrequency Catheter Ablation in Infancy

It is difficult to make a definitive diagnosis of congenital junctional ectopic tachycardia (JET) in utero. We report a case in which congenial JET was suspected by fetal M‐mode echocardiography. Fetal M‐mode tracing of the atria and ventricle clearly showed a gradual acceleration of ventricular activity at the beginning of tachycardia, the warming‐up sign of ectopic tachycardia, which was followed by simultaneous contractions of atrium and ventricle. This report also describes successful emergent radiofrequency catheter ablation of congenital JET in infancy with preservation of normal AV nodal conduction for this patient.

Soft magnetic properties of Fe-TM-C-N (TM:Zr,Nb) nanocrystalline films

Soft magnetic properties of Fe-TM-C-N (TM:Zr,Nb) films, fabricated by RF reactive sputtering in Ar/sup +/N/sub 2/ atmosphere, were investigated. The as-deposited films having mixed phases of amorphous and /spl alpha/-Fe or mostly crystalline /spl alpha/-Fe phase showed nanocrystalline structure upon annealing. The best soft magnetic properties achieved in these films are; H/sub c/ of 0.06 Oe, /spl mu//sub eff/ 2750 (1 MHz) and 4 /spl pi/Ms, of 16.8 kG in Fe-Zr-C-N film and H/sub c/ of 0.31 Oe, /spl mu//sub eff/ of 2100 (1 MHz) and 4 /spl pi/Ms of 15.5 kG in Fe-Nb-C-N film. The fine grained /spl alpha/-Fe structure, together with very fine TM(C,N) precipitates which were formed at an early stage of crystallization, is considered to be one of the main factors for the excellent soft magnetic properties. The Fe-Zr-C-N films exhibit better soft magnetic properties than those of the Fe-Nb-C-N films, which is considered to be due to the magnitude of the formation enthalpy.

Effects of the interlayer on the magnetic properties of Fe-Hf-C/ceramics multilayered films

The magnetic properties of nanocrystalline FeHfC single layered and FeHfC/ceramics (AlN, Al/sub 2/O/sub 3/, Si/sub 3/N/sub 4/, SiO/sub 2/) multilayered films were investigated. The soft magnetic properties of the multilayered films laminated by the Al-based ceramics were better, but those of films laminated by the Si-based ceramics were worse than the magnetic properties of single layered films. An analysis of multilayered structure revealed that FeHfC/AlN and FeHfC/Al/sub 2/O/sub 3/ films maintained better periodic structure than FeHfC/Si/sub 3/N/sub 4/ and FeHfC/SiO/sub 2/ films. The present results suggest that the interdiffusion effect plays an important role in determining the magnetic properties of the multilayered films. >