Ablation of Atrial Flutter in a Patient With Mustard Procedure Using Integration of Real-Time Electroanatomical Mapping With 3-Dimensional Computed Tomographic Imaging
A 24-year-old woman with a history of surgical palliation of d-transposition of the great arteries, a systemic ejection fraction of 66%, and symptomatic atrial flutter with rapid ventricular response was referred for an electrophysiological study and ablation procedure. At 6 months of age, she had undergone a Mustard (atrial switch) procedure, whereby a “baffle” was surgically constructed within her atria to direct systemic venous blood across the mitral valve into the left ventricle (systemic venous ventricle) and the pulmonary artery, and pulmonary venous blood across the tricuspid valve into the right ventricle (pulmonary venous ventricle) and the aorta. Her ECG, which shows atrial flutter with a ventricular rate of 262 beats per minute with 1:1 atrioventricular conduction, is illustrated in Figure 1.
The procedure was performed under the guidance of the CARTO-MERGE electroanatomical mapping system (Biosense Webster, Inc., Diamond Bar, Calif.). After creation of a 3-dimensional anatomic construct from a high-resolution contrast-enhanced cardiac computed tomography, the cardiac structures were segmented (Figure 2). Integration of the computed tomography images with real-time intraprocedural electroanatomical mapping was performed by registration of the corresponding anatomic points inside the aorta. The resulting image allowed virtual navigation of the ablation catheter inside 3-dimentionally accurate anatomic cardiac structures. After construction of the map, a recording catheter was placed in the venous baffle and another in the apex of the systemic venous ventricle (SVV). With rapid pacing from inside the baffle, an atrial flutter with a cycle length of 295 ms was inducible. A mapping catheter was advanced via the aorta and the pulmonary venous ventricle via femoral arterial access to the pulmonary venous atrium (PVA) in a retrograde fashion (Figure 2). Entrainment mapping localized the tachycardia circuit to the tricuspid annulus (TA), an isthmus that spans the floor of the PVA and also the adjacent region inside the baffle (Figure 3). Multiple radiofrequency applications were delivered to the floor of the PVA near the TA, which resulted in progressive prolongation of the tachycardia cycle length without termination. However, after delivery of additional radiofrequency lesions to the floor of the baffle in an area adjacent to the TA isthmus and the PVA (Figure 3), the arrhythmia was successfully terminated. At the end of the procedure, atrial flutter was no longer inducible and the patient has remained free of arrhythmias during follow-up.
Intraatrial reentrant tachycardias are frequently seen in patients with surgically repaired d-transposition of the great arteries.1 Among these patients, TA isthmus–dependent reentry is most common and accounts for as many as 77%.2 Whereas in some patients catheter ablation that targets the TA isthmus via a retrograde approach and from inside the baffle can achieve favorable outcomes,2,3 in other patients it may also be necessary to target additional isthmus sites inside the PVA via a transbaffle/transseptal approach.4 Such procedures can pose a great technical challenge and require accurate identification of key anatomic locations and landmarks inside surgically modified structures. In this case, the image integration system remarkably enhanced the ablation of the atrial flutter in this patient in that it enabled us to visualize the ablation catheter in relation to the complex cardiac anatomy with great accuracy and fine detail. This approach may also prove highly useful in mapping and ablation of cardiac arrhythmias in patients with other types of complex congenital heart disease.
Dr Ruskin and Dr Mansour have received honoraria from and have served on the Advisory Board or consulted for Biosense Webster Inc. The other authors report no conflicts.
Zrenner B, Dong J, Schreieck J, Ndrepepa G, Meisner H, Kaemmerer H, Schomig A, Hess J, Schmitt C. Delineation of intra-atrial reentrant tachycardia circuits after mustard operation for transposition of the great arteries using biatrial electroanatomic mapping and entrainment mapping. J Cardiovasc Electrophysiol. 2003; 14: 1302–1310.