"Figure-of-8" Intra-Atrial Re-Entry Tachycardias in
Post-Operative Patients with Congenital Heart Disease

Parvin Dorostkar

Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland Heights, USA

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1.  Introduction

Post-operative atrial tachycardias continue to plague patients after correction for congenital heart disease. Intraatrial mapping in association with traditional electrophysiologic techniques and ablation has offered new ways to analyze and interpret complex tachycardias in post-operative patients. The addition of electroanatomic mapping has offered better understanding of the tachycardia mechanism, and, therefore more successful ablation of these tachycardias. We describe a small cohort of complex atrial reentry tachycardias in post-operative patients with congenital heart disease.

2.  Methods

After appropriate consent, a cohort of 21 symptomatic post-operative patients had 33 atrial tachycardias mapped. Of these 33 tachycardias, 6 were noted to inscribe a "Figure-of-8" intraatrial reentrant tachycardia. Two of these were observed in patients after simple atriotomies, whereas 4 were observed in patients after complex atriotomies.

3.  Results

Six of 33 mapped tachycardias inscribed a "Figure-of-8" intra-atrial reentrant tachycardia. Two of these tachycardias were noted after a simple atriotomy. One of these was noted in a patient after Tetralogy of Fallot repair and one in a patient with Ebstein's anomaly after tricuspid valve replacement. The remaining four "Figure-of-8" tachycardias occurred in patients after complex atriotomies. Two of these occurred in patients with transposition of the great arteries after a Senning operation and two occurred in patients with single ventricle physiology (double inlet left ventricle in one and tricuspid atresia in another patient). The mean age of these patients was 26.8 +/- 10.8 years. The mean cycle length of the tachycardias was 269 +/- 20 msecs.

3.1. Characteristics of "Figure-of-8" Intraatrial Tachycardia in Patients After Simple Atriotomy

One patient with Tetralogy of Fallot had a history of a previous unsuccessful ablation of an atrial reentry tachycardia. Repeat study of the same tachycardia revealed a "Figure-of-8" atrial tachycardia, which was previously missed. This tachycardia was noted to have a common isthmus between a suspected atriotomy (mapped double potentials) and the inferior vena cava. Ablation of the common isthmus resulted in successful treatment of this tachycardia.

A second patient with Ebstein's anomaly received multiple ablative lesions in the subeustachian isthmus, which did not result in tachycardia termination. Retrospective evaluation revealed a "Figure-of-8" tachycardia with a common isthmus between an anterior atriotomy and posterolateral double potentials. This complex mechanism was not recognized at the time of the study and, therefore, this tachycardia was not successfully ablated.

3.2.   Characteristics of "Figure-of-8" Intraatrial Tachycardia in Patients After Complex Atriotomy

"Figure-of-8" tachycardia with a common isthmus in the systemic venous atrium involved clockwise propagation around a scar and/or double potentials in the right lateral free wall and counterclockwise propagation around anterior atrial incisions that were left from surgery associated with the Senning operation for transposition of the great arteries. A long ablative lesion bridging the superior and inferior parts of the Senning surgical baffle resulted in successful ablation with no recurrence of tachycardia in more than 4 years.

"Figure-of-8" tachycardia in the pulmonary venous side, involved counterclockwise propagation around the mitral valve annulus and clockwise propagation around double potentials recorded on the lateral right free wall of the pulmonary venous atrium. Successful ablation was achieved from the posterolateral right free wall of the pulmonary venous atrium to the mitral valve.

Another two "Figure-of-8" tachycardias were noted in patients after Fontan operations. One of these demonstrated a common isthmus between an anterior atriotomy and an atrial septal defect patch and was successfully ablated. The second "Figure-of-8" tachycardia could not be ablated presumably because a transmural lesion could not be achieved. Ablative lesions from the right atrial posterolateral wall to both the IVC and the tricuspid valve dimple did not result in successful ablation of this tachycardia. This patient has had no clinical recurrence after 8 months of follow-up.

3.3.   Ablation of "Figure-of-8" Intraatrial Reentry Tachycardia

In patients with "Figure-of-8" atrial tachycardias application of radiofrequency energy to the common isthmus between the two loops was used to target successful ablation. In patients with a simple atriotomy a "Figure-of-8" intraatrial reentry tachycardia was noted in a patient with Ebstein's anomaly after tricuspid valve replacement and in a patient after Tetralogy of Fallot repair. One of these was successfully ablated. The other "Figure-of-8" intraatrial reentrant tachycardias occurred in patients after complex atriotomy. Two of these occurred in patients with transposition of the great arteries after Senning operation. Both of these could be successfully ablated. The final two "Figure-of-8" reentry tachycardias occurred in patients after a Fontan operation. One of these could not be successfully ablated. The overall success rate by targeting the common isthmus between the two loops of a "Figure-of-8" intraatrial tachycardia is 4 out 6. We suspect that the failure rate was in part related to the inability to achieve a transmural lesion.

4.  Conclusions

Complex "Figure-of-8" intraatrial reentry tachycardias can occur in patients after simple or complex atriotomy for congenital heart disease, but appear to be more common in patients after complex atriotomies for repair or palliation of congenital heart disease. These tachycardias appear not to be subeustachian isthmus dependent.