Successful ablation of cavo-tricuspid isthmus dependent atrial flutter in a patient with Senning operation/Senning operasyonlu hastada kavo-triküspit istmus bagimli atriyal flutterin basarili ablasyonu

Introduction

Atrial flutter is a common complication late after atrial switch operation for transposition of the great arteries. It is usually cavotricuspid isthmus (CTI) dependent (1). Radiofrequency catheter ablation (RFCA) targeting CTI region may eliminate flutter (2). Access to targets for ablation may be limited by anatomy and by surgically placed obstacles. We report a case in which bidirectional CTI block achieved under computed tomography (CT) and electro-anatomic mapping (EAM) system guidance terminated the tachycardia.

Case Report

A-16-year old boy with a history of surgical palliation of d-transposition of the great arteries, a normal systolic ejection fraction, and symptomatic drug refractory atrial flutter was referred for an electrophysiological study and ablation procedure. At the age of 3 months he had undergone a Senning (atrial switch) operation. A baffle was surgically constructed within atria for directing systemic venous blood across the mitral valve into the leftventricle (systemic venous ventricle) and the pulmonary artery, and pulmonary venous blood across the tricuspid valve into right ventricle (pulmonary venous ventricle) and the aorta. His electrocardiogram (ECG) showed atrial flutter with a ventricular rate of 142 beats per minute (Fig. 1). A transesophageal echocardiography was performed to rule out intra-cardiac thrombus. He underwent a contrast-enhanced computed tomography for detailed anatomic evaluation (Fig. 2).

The procedure was performed under the guidance of the CARTO-XP electroanatomical mapping system (Biosense Webster, Inc., CA, USA). A mapping catheter was placed in the venous baffle and the other in the apex of the systemic ventricle. An atrial flutter with a 214 ms cycle length and 2:1 AV conduction ratio was recorded. The ablation catheter was advanced to the aorta and the pulmonary venous ventricle via femoral arterial access to the pulmonary venous atrium in a retrograde fashion. Electroanatomic maps of the pulmonary venous atrium and systemic venous atrium were created. Voltage map showed large scar area in the pulmonary venous atrium (Fig. 3A and B). Entrainment mapping demonstrated that flutter circuit was CTI dependent. A line of double potentials was found along the septal systemic venous atrium into the baffle. Both ablation lesions were created via transaortic access to the tricuspid annulus and zone between inferior vena cava and the baffle via femoral venous access, which terminated the tachycardia (Fig. 3C). Pacing maneuvers were confirmed bidirectional isthmus block. At the end of the procedure there was no inducible atrial flutter. Echocardiography performed immediately and 1 day after the procedure demonstrated no pericardial effusion. No tachycardias were documented during 2 days of continuous in-hospital ECG monitoring. During a month follow up, he remained in sinus rhythm.

Discussion

Atrial flutter is common in patients with congenital heart disease, especially in patients with transposition of the great arteries who had undergone palliative atrial switch operations. Most of these tachyarrhythmias are CTI dependent, but the critical zones of slow conduction between suture line and superior vena caval orifice, mitral valve annulus, and pulmonary vein orifice have all been described. Focal atrial tachycardias adjacent to suture lines are also common (1). Cavotricuspid isthmus ablation is a therapeutic option in CTI dependent flutters (2). But it can be limited because of complex cardiac anatomy and large scars due to previous surgery. In the atrial switch population, the coronary sinus (Cs) ostium (os) and tricuspid valve annulus are often on the pulmonary venous atrial side, rather than the systemic venous atrial side. Catheter access to this area necessitates a difficult retrograde approach from the aorta to the right ventricle and then posterior toward the tricuspid annulus and CS os. In our case, after the failure of several ablation attempts from systemic venous atrial side, we decided to reach to the CTI by aortic retrograde access. Bernhardzrenner et al. (3) reported a case in which for successful ablation creation of the ablation lesions to both sides of the baffle line, and creation of bidirectional block were necessary. We also paced the patient from different sides to confirm bidirectional isthmus conduction block. However in some patients, ablating from both sides of the atria cannot eliminate the flutter, and additional ablation lines via transbaffle puncture may be needed (4).

Such procedures may be challenging due to the complex cardiac anatomy and accurate identification of key anatomic locations and landmarks are important for successful ablation. Merging the anatomic data and electrophysiologic data may increase success rates.

Conclusion

In our case both contrast-enhanced computed tomography and electroanatomical mapping system were used for guiding the procedure. Voltage mapping demonstrated a large scar area adjacent to the baffle. Fragmented and double potentials were recorded, indicating slow conduction zones. To achieve CTI block application of the RF energy from the both sides of the baffle was used. Our case demonstrates RF ablation of CTI is a safe and effective therapeutic modality of drug refractory atrial flutters in patients with Senning operation.

References

References

1. Kanter RJ. Pearls for ablation in congenital heart disease. J Cardiovasc Electrophysiol 2010; 21: 223-30. [CrossRef]

2. Kanter RJ, Papagiannis J, Carboni MP, Ungerleider RM, Sanders WE, Wharton JM. Radiofrequency catheter ablation of supraventricular tachycardia substrates after Mustard and Senning operations for d-transposition of the great arteries. J Am Coll Cardiol 2000; 35: 428-41. [CrossRef]

3. Dong J, Zrenner B, Schreieck J, Schmitt C. Necessity for biatrial ablation to achieve birectional cavotricuspid isthmus conduction block in a patient following Senning operation. J Cardiovasc Electrophysiol 2004; 15: 945-9. [CrossRef]

4. Perry JC, Boramanand NK, Ing FF. "Transseptal" technique through atrial baffles for 3-dimensional mapping and ablation of atrial tachycardia in patients with d-transposition of the great arteries. J Interv Card Electrophysiol 2003; 9: 365-9. [CrossRef]