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Concealed AP with Slow and Incremental Conduction. We report a peculiar form of permanent junctional reciprocating tachycardia that occurs only during daytime and physical activity. ECG obtained during tachycardia showed an unusual progressive shortening of the ventriculoatrial (VA) interval that was maximal at the first complex and shortest at the last one before block occurred, always at the accessory pathway level. This phenomenon has not been previously described and appears to be a reverse type of Wenckebach block. It was observed during salvos of spontaneous tachycardia and could be reproduced by right ventricular pacing. The accessory pathway was ablated successfully at the right posteroseptal region, close to the coronary sinus ostium. After ablation, there was no VA conduction, and tachycardia did not recur during a 9-month follow-up period.

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Estudos eletrofisiológicos têm comprovado a existência de vias acessórias atípicas que apresentam características funcionais semelhantes ao nó atrioventricular (AV), ou seja, propriedade de conduçäo decremental. Diferente das vias anômalas convencionais, nas quais a conduçào anterógrada e/ou retrógrada se faz de maira rápida, essas vias conduzem o estímulo elétrico de forma lenta. A presença no circuito reentrante de duas estrutras de conduçäo lenta do tipo nodal AV permite, por vezes, a manutençäoa taquiarritmia originando as formas permanentes ou incessante. Seräo revisadas as vias anômalas de conduçäo decremental anterógradas e retrógradas, apresentando o estado de arte da técnica de ablaçäo com radiofrequência (RF), em um grupo de pacientes submetidos ao procedimento em nossa institutiçäo.

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A case of a 20 year old young man having the permanent form of junctional reciprocating tachycardia complicated by ventricular fibrillation (VF) is reported. A number of antiarrhythmic drugs either as single or combined therapy fail to control tachycardia. Paroxisms of a faster palpitation which never lasted longer than a few minutes were felt over the last six months before the occurrence of VF. At admission, a narrow QRS tachycardia 250 beats/min was recorded and soon degenerated into VF. After electrical shock with 350J permanent form of junctional tachycardia resumed. Electrophysiologic evaluation identified an accessory pathway with long conducting times in postero-septal location, enhanced atrioventricular node conduction and inducible atrial flutter. The patient underwent successful radiofrequency ablation and is doing well after 18 months of follow-up, being off antiarrhythmic drug and tachycardia free.

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Homem de 20 anos, portador de taquicardia de apresentaçäo incessante há longos anos, sem resposta a medicaçöes antiarrítmicas. Seis meses antecedendo a admissäo referia paroxismos de taquicardia mais rápida, de duraçäo curta, autolimitada. Na admissäo apresentava flutter atrial com conduçäo 1:1 (250 bpm) que degenerou em fibrilaçäo ventricular, revertida com 350J. O estudo eletrofisiológico identificou taquicardia atrioventricular, utilizando conexäo anômala "oculta" de localizaçäo póstero-septal deita com conduçäo lenta e propriedade decremental, conduçäo atrioventricular acelerada, observando-se precipitaçäo de fibrilaçäo atrial com resposta rápida pós-atropinizaçäo. Foi submetido a ablaçäo por cateter pro radiofrequência com sucesso. Esta assintomático, 18 meses após o procedimento.

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We report on a patient with paroxysmal left bundle branch block-like tachycardia with electrophysiologic findings suggestive of nodoventricular pathway (ventricular pre-excitation dependent on slowing of AV conduction, and accessory pathway with exclusive anterograde conduction). There was no pre-excitation during sinus rhythm but it was brought on by intravenous verapamil. Atrioventricular node conduction curves showed no signs of duality. Diagnosis of an atriofascicular pathway with decremental properties was based on the following findings: 1) absence of AV dissociation during reciprocating tachycardia; 2) absence of fusion beats or narrowing QRS complexes during tachycardia; 3) advancement of right ventricular activation with late atrial extrastimuli delivered during antidromic tachycardia at a time of low right atrium refractoriness; 4) observation that earliest ventricular endocardial electrogram during tachycardia (activation mapping) was simultaneous with the right bundle potential; 5) surgical ablation of the accessory pathway by endocardial incision at the right anterior aspect of the tricuspid ring, far away from the AV node region. Evidences showing anterograde longitudinal dissociation of the accessory pathway included cycle length alternation during tachycardia and duality of accessory pathway conduction times and refractory periods. We hypothesize that reentry occurring in such AV node-like structure could give to a pre-excited tachycardia with AV dissociation mimicking antidromic tachycardia associated with nodoventricular pathway.

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A case of surgical treatment for reentrant atrioventricular tachycardia in a 7 months old child is reported. Episodes of tachycardia were repetitive and long-lasting, often leading to signs of hemodynamic impairement, and were not controlled by antiarrhythmic drugs. The electrophysiologic study showed a circus-movement tachycardia utilizing a concealed accessory pathway located at the anterior septal aspect of tricuspid anulus. The child underwent successful surgical treatment by the endocardial technique. Few minutes after weaning from extracorporeal circulation, developed T wave inversion followed by acute right ventricular dysfunction and ventricular fibrillation. Others ischemic like episodes, maybe as a result of coronary artery spasm, occurring in the next 6 hours were successfully treated with isosorbide dinitrate. At 18 months follow-up, the child is free of tachycardia and has normal atrioventricular conduction.

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A case of recurrent ventricular tachycardia in the setting of chronic chagasic heart disease refractory to conventional antiarrhythmic agents as well as high doses of amiodarone (600 mg/day) is reported. Left ventriculography disclosed an apical aneurysm and a filling defect image suggestive of a thrombus. Sustained monomorphic ventricular tachycardia with the same QRS configuration as "clinical" tachycardia could be induced by means of right ventricular programmed electrical stimulation. The risk of systemic embolization precluded endocardial activation mapping of ventricular tachycardia. Intracoronary cold saline injections were done during induced ventricular tachycardia looking for a coronary artery branch related to the arrhythmogenic substrate. Cold saline mapping results pointed to an apical site of origin. Next step was intracoronary injection of ethyl alcohol in the distal part of the left anterior descending artery leading to a small and uncomplicated myocardial infarction. Control programmed stimulation was unable to reinduce ventricular tachycardia. Clinical outcome was uneventful and there was no recurrence of clinical arrhythmia in 6 months of follow-up.

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A case of severe dilated cardiomyopathy in a young boy presenting with incessant ventricular tachycardia, who had been referred for heart transplantation is reported. Complete resolution of dilated cardiomyopathy followed arrhythmia control with oral amiodarone. Such evolution strongly suggests a cause-effect relationship between incessant ventricular tachycardia and dilated cardiomyopathy in this particular case.

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A 30 year-old male patient with arrhythmogenic right ventricular dysplasia was submitted to implantation an automatic cardioverter-defibrillator. So far he is well in a follow-up of 7 months.

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