Successful Ablation of Atrial Tachycardia Originating from Inside the Single Atrium and Conduit After a Fontan Operation.

An 18-year-old male who had a past medical history of an intracardiac total cavopulmonary connection (TCPC) operation was referred to our hospital for radiofrequency catheter ablation (RFCA) of supraventricular tachycardia (SVT). Two types of SVTs were induced, and 3-dimensional (3D) maps were created using an ultra-high-density 3-dimensional mapping system (Rhythmia). The earliest atrial activation site (EAAS) of SVT1 was at the superior part of the conduit, and the EAAS of SVT2 was at the inferior part of the single atrium (SA). The SVTs were terminated by energy deliveries to the EAAS from the conduit in SVT1 and from inside the single atrium in SVT2. Detailed maps of the SVTs were important to understand the mechanisms of the SVTs. The Rhythmia system was useful for the detailed mapping of complex arrhythmias. The use of Rhythmia in patients after a TCPC is difficult, because puncturing the TCPC conduit and proceeding and manipulating the Orion catheter via a narrow puncture hole are difficult. We were the first to succeed in ablating two atrial tachycardias (ATs) originating from the inside and outside of the conduit after a TCPC operation by using an ultra-high-density 3-dimensional mapping system.

Successful control of life-threatening polymorphic ventricular tachycardia by radiofrequency catheter ablation in an infant.

We present a case of a 9-month-old girl in whom malignant polymorphic ventricular tachycardia (VT) was successfully controlled by radiofrequency catheter ablation under guidance with a three-dimensional mapping system. The VTs originated from the left ventricular lateral wall, left ventricular anterior wall, and left ventricular apex. At least six types of VTs were documented during the electrophysiology study. All VTs were successfully controlled after two sessions of radiofrequency catheter ablation, and she was discharged from our hospital on propranolol, mexiletine, flecainide, and aprindine.

Improvement in non-tachycardia-induced cardiac failure after radiofrequency catheter ablation in a child with a right-sided accessory pathway.

A 6-year-old boy was referred for an evaluation of intolerance to physical activity at his elementary school. The patient had no episodes of palpitations. He was diagnosed as Wolff-Parkinson-White syndrome with a right-sided accessory pathway (AP) and dilated cardiomyopathy (DCM). Ventricular dyskinesis was detected mostly in the ventricular septum. Because the asynchronous septal motion caused by pre-excitation through a right-sided AP might deteriorate his cardiac function, he underwent an AP ablation, after which the asynchronous ventricular wall motion disappeared and the wall thickness improved. We suggest that an AP ablation may be the treatment of first priority in patients who have DCM-like dyskinesis even without sustained tachyarrhythmias.

A connexin40 mutation associated with a malignant variant of progressive familial heart block type I.

BACKGROUND: Progressive familial heart block type I (PFHBI) is a hereditary arrhythmia characterized by progressive conduction disturbances in the His-Purkinje system. PFHBI has been linked to genes such as SCN5A that influence cardiac excitability but not to genes that influence cell-to-cell communication. Our goal was to explore whether nucleotide substitutions in genes coding for connexin proteins would associate with clinical cases of PFHBI and if so, to establish a genotype-cell phenotype correlation for that mutation. METHODS AND RESULTS: We screened 156 probands with PFHBI. In addition to 12 sodium channel mutations, we found a germ line GJA5 (connexin40 [Cx40]) mutation (Q58L) in 1 family. Heterologous expression of Cx40-Q58L in connexin-deficient neuroblastoma cells resulted in marked reduction of junctional conductance (Cx40-wild type [WT], 22.2±1.7 nS, n=14; Cx40-Q58L, 0.56±0.34 nS, n=14; P<0.001) and diffuse localization of immunoreactive proteins in the vicinity of the plasma membrane without formation of gap junctions. Heteromeric cotransfection of Cx40-WT and Cx40-Q58L resulted in homogenous distribution of proteins in the plasma membrane rather than in membrane plaques in ≈50% of cells; well-defined gap junctions were observed in other cells. Junctional conductance values correlated with the distribution of gap junction plaques. CONCLUSIONS: Mutation Cx40-Q58L impairs gap junction formation at cell-cell interfaces. This is the first demonstration of a germ line mutation in a connexin gene that associates with inherited ventricular arrhythmias and emphasizes the importance of Cx40 in normal propagation in the specialized conduction system.

Life-threatening atrial tachycardia after the Senning operation in a patient with transposition of the great arteries.

Atrial tachycardia (AT) is recognized as a risk factor of sudden death (SD) in patients with transposition of the great arteries (TGA) after atrial switch operation. A 20-year-old man with TGA who had undergone a Senning operation experienced a near-miss SD event 1 day after appearance of AT. He was successfully resuscitated by electrical defibrillation for documented ventricular fibrillation. An electrophysiological study showed three types of AT, and all of them were terminated by radiofrequency catheter ablation (RFCA). We consider that symptomatic AT against cardiac medications is indicated for RFCA therapy.

Electrophysiological characteristics of idiopathic ventricular tachycardia in children.

BACKGROUND: Idiopathic ventricular tachycardia (VT) has been reported to have a good prognosis, but there still might be the potential risk of sudden death. METHODS AND RESULTS: The 46 consecutive children (mean age 11.7 ± 3.4 years) with idiopathic VT were enrolled in this study. Monomorphic VT was detected in 39 patients and polymorphic VT in 7 patients. The VT originated from the right ventricle (RV) in 22 patients, and left ventricle (LV) in 17 patients. The VT was induced by exercise in 68% of the RVVT, 41% of the LVVT, and 100% of the polymorphic VT. The VT was induced by programmed ventricular stimulation in 41% of the RVVT, 35% of the LVVT, and none of the polymorphic VT. Adenosine tri-phosphate terminated the VT in 9 of 15 patients (60%). The mechanism of the VT was suspected to be triggered by activity in 36.4%, automaticity in 40.9%, and re-entry in 22.7% of the RVVT, whereas it was 52.9%, 5.9%, and 41.2% of the LVVT, respectively. CONCLUSIONS: The exercise inducibility was higher in polymorphic VT than the RVVT and LVVT, but no difference in the programmed stimulation. The sensitivity to adenosine tri-phosphate was not different between the RVVT and LVVT. In some patients with idiopathic VT, a non-verapamil sensitive re-entry was documented, which was more common in patients with ischemic heart disease or cardiomyopathy.

Decremental accessory pathway conduction after ablation and antidromic atrioventricular reciprocating tachycardia 8 years after successful radiofrequency ablation.

INTRODUCTION: This is a rare case of antidromic reciprocating tachycardia developing 8 years after successful catheter ablation. RESULT: A 15-year-old girl had recurrence of palpitations 8 years after the ablation of manifest right posteroseptal accessory pathway. Atrial burst pacing revealed Wenckebach atrioventricular conduction with preexcitation. Wide QRS tachycardia with identical morphology to sinus rhythm associated with retrograde His potential recorded immediately after the V-wave was induced by isoproterenol infusion. Atrial premature stimulus applied at the identical timing of His potential advanced the subsequent ventricular beat and His potential. CONCLUSION: Catheter ablation may produce decremental accessory pathway conduction and rarely cause antidromic atrioventricular reciprocating tachycardia. This may be explained by a presence of "de novo" accessory pathway with decremental conduction properties that became manifest after the first ablation.

Novel SCN5A mutation (Q55X) associated with age-dependent expression of Brugada syndrome presenting as neurally mediated syncope.

BACKGROUND: An association between Brugada syndrome and neurally mediated syncope has been described. Although mutations in SCN5A have been identified in Brugada syndrome, the genetic link between Brugada syndrome and neurally mediated syncope has not been determined. OBJECTIVES: The purpose of the study was to clinically and genetically characterize a man with recurrent syncope that originally was diagnosed as neurally mediated syncope at age 8 years but subsequently manifested as Brugada syndrome at age 17 years. METHODS: The proband underwent clinical examination, which included head-up tilt test, sodium channel provocation test, and electrophysiologic study. Genetic screening of SCN5A was performed for the proband and his family members. The biophysical properties of a mutant SCN5A channel in a heterologous expression system were studied using whole-cell, patch clamp technique. RESULTS: The proband showed positive head-up tilt test, coved-type ST elevation recorded from the third intercostal space, and positive pilsicainide provocation test. Ventricular fibrillation was inducible at programmed electrical stimulation, consistent with characteristics of both Brugada syndrome and neurally mediated syncope. A novel nonsense SCN5A mutation (Q55X) was identified in the proband, his mother, and his asymptomatic brother. The heterologously expressed mutant channel was nonfunctional. CONCLUSION: We genetically determined an SCN5A mutation in a patient showing the combined phenotype of neurally mediated syncope and Brugada syndrome. Neurally mediated syncope and Brugada syndrome may share, at least in part, a common pathophysiologic mechanism.