[Placement of permanent epicardial pacemaker in a newborn with congenital complete AV block]. / Colocación de marcapaso epicárdico permanente en un recién nacido con bloqueo AV completo congénito.

Isolated congenital atrioventricular block is reported in one out of 20,000 live births. The optimistic view on the prognosis and indications for permanent pacing have been modified in the last 35 years. The purpose of this report is to present a prenatally diagnosed case, outlining the surgical technique for permanent pacing. The infant was a male born by cesarean section, weighted 3030 grs and had a structurally normal heart. His ECG showed complete AV block with narrow QRS, atrial rate was 140 and ventricular rate was 55. We implanted a epicardial pacemaker VVIR by midline laparatomy. The lead was unipolar 35 cms long screw-in type and was placed in the right ventricle through the xiphoid process. The pacemaker was placed in a GoreTex bag and fixed intraperitoneal to the abdominal wall. The infant did well after the procedure and he was discharged in good condition one week later. We conclude that it is appropriate to implant a permanent pacemaker in these patients with low ventricular rate thus reducing the risk of sudden cardiac death. The surgical technique is safe and makes easy the generator replacement.

[The radiofrequency ablation of a left lateral accessory pathway during pre-excitation atrial fibrillation]. / Ablación con radiofrequencia de una vía accesoria lateral izquierda durante fibrilación auricular pre-excitada.

The occurrence of atrial fibrillation during an electrophysiologic study in patients with Wolff-Parkinson-White syndrome is a common problem and it is time-consuming to terminate it either with the use of drugs or by electrical cardioversion. The purpose of this report is to assess the feasibility of successful radiofrequency catheter ablation of and mapping for overt left-sided accessory pathway during atrial fibrillation. During an electrophysiologic study, pre-excitation was lost and the patient developed sustained atrial fibrillation either spontaneously or during catheter manipulation. We decided to map during this arrhythmia because we noted that the patient had maximally pre-excited beats which might increase the possibility of accessory pathway potential recording and a successful ablation site. With the ablation catheter in the left-lateral region we recorded an early ventricular electrogram and a rapid deflection preceding the onset of ventricular activation that was not observed in non pre-excited beats and we considered it the Kent potential. At this site we applied one pulse of radiofrequency current with temperature control at 70 degrees C and eliminated anterograde conduction over the accessory pathway during the first 3 seconds and continue the radiofrequency current for a total of 2 minutes. The procedure time was 60 minutes. We conclude that mapping and radiofrequency catheter ablation can be successfully performed during pre-excited atrial fibrillation and this could shorten the procedure and obviate the need for several electrical cardioversions.

[Radiofrequency ablation of permanent supraventricular tachycardia through an accessory pathway with slow retrograde conduction]. / Ablación con radiofrecuencia de taquicardia supraventricular incesante por una vía accesoria con conducción retrógrada lenta.

We present the case of a 6 year old boy with permanent junctional reciprocating tachycardia. The tachycardia had been present since 3 years before ablation and was treated with two drugs without good control. He began to complain of palpitations and shortness of breath on exertion and the left ventricle ejection fraction was 55% by echocardiography. We performed an electrophysiologic study which showed the most early atrial activation at the coronary sinus with a long V-A interval. Orthodromic AV reciprocating tachycardia was confirmed as the mechanism of tachycardia by demonstrating atrial pre-excitation when a premature ventricular stimulus was delivered at the time the His bundle was refractory. With the ablation catheter, the accessory pathway potential was recorded at the coronary sinus near the os. Radiofrequency current was applied with temperature control at 60 degrees C for one minute at this site with success. While on sinus rythm we performed programmed atrial and ventricular stimulation with isoproterenol infusion and there was no evidence of accessory pathway function. This patient is asymptomatic and on sinus rythm 6 months later.