ELECTROPHYSIOLOGY
Pivotal role of integrated electroanatomic mapping with three-dimensional multislice computed tomography scan in the ablation of a left atrial ectopic focus
Unidad de Arritmias, Instituto Cardiovascular, Hospital Clínico Universitario San Carlos. C./Profesor Martín Lagos s/n. 28040 Madrid, Spain
Manuscript submitted 13 March 2006. Accepted after revision 1 August 2006.
* Corresponding author. Tel: +34 91 3303527; fax: +34 91 3303527. E-mail address: nperez.hcsc{at}salud.madrid.org
Key Words: Catheter ablation, Atrial tachycardia, Mapping, Anatomy, Computed tomography
A 25-year-old woman without structural heart disease was referred to our centre for ablation of incessant left atrial tachycardia (Figure 1). An automatic ectopic focus was located to the left atrial appendage by conventional electroanatomic mapping (CARTO®, Biosense Webster Inc., Diamond Bar, CA, USA). Twenty-five radiofrequency applications were delivered at the area of earliest atrial activation (–25 ms from the P wave onset) through a 3.5 mm irrigated tip ablation catheter (Navi-Star® Thermo-Cool®, Biosense Webster Inc., Diamond Bar, CA, USA), using a power limit of 35 W, but tachycardia was not interrupted. Epicardial mapping via the coronary sinus did not provide better positions for radiofrequency delivery. Epicardial electroanatomic mapping was performed via percutaneous transpericardial access in a second procedure. The earliest atrial activation (–30 ms from the P wave onset) was recorded at the area of the left atrial appendage, next to the left anterior descending artery, but again cooled ablation was unsuccessful (Figure 2). In the following months several antiarrhythmic drugs were tried, but the patient remained severely symptomatic in incessant atrial tachycardia and a new percutaneous or surgical ablation attempt was indicated.
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A thoracic contrast-enhanced 64-slice computed tomography (CT) scan (Aquillon®, Toshiba Medical Systems Corp., Tokyo, Japan) was performed. Computed tomography images were transferred to the CARTO® system (CartoMerge®, Biosense Webster Inc., Diamond Bar, CA, USA).1
The integrated electroanatomic map allowed us to guide the ablation catheter to the distal left atrial appendage, which turned out to be technically demanding due to a local narrowing of the left atrial appendage lumen. In fact, this area had been missed in the previous endocardial ablation attempt. Intermittent mechanical block of the ectopic focus was induced at the tip of the left atrial appendage, and cooled radiofrequency ablation at this point was successful (Figures 3 and 4).
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The use of multislice CT scans may reveal singular anatomic findings that may be associated with tachyarrhythmia substrates and/or explain the failure of previous ablation attempts. Although especially designed for atrial fibrillation ablation, image integration in electroanatomic mapping systems may also improve the efficacy of catheter ablation in other complex arrhythmic substrates.
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[1] Dong J, Calkins H, Solomon SB, Lai S, Dalal D, Lardo A, et al. Integrated electroanatomic mapping with three-dimensional computed tomographic images for real-time guided ablations. Circulation 2006; 113: 186–194.
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