Utility of Non-Contact Three-Dimensional Mapping of the Left<br />
Atrium for Ablation of Left Atrial Tachycardia

ABSTRACT: A 78-year-old man with a highly symptomatic left atrial tachycardia, refractory to medical therapy, was referred for radiofrequency catheter ablation. Using a double trans-septal technique, two long sheaths were placed across the interatrial septum into the left atrium. Using a 64-electrode non-contact three-dimensional mapping technique, the left atrium was reconstructed and the focus localized to the right superior pulmonary vein ostium. Radiofrequency energy was applied and eliminated the ectopic focus. In summary, a three-dimensional non-contact mapping catheter can facilitate ectopic left atrial tachycardia ablation. Case Report. A 78-year-old man with a long-standing history of palpitations refractory to medical therapy including calcium channel and beta-blockers, was referred for a left atrial tachycardia ablation. Figure 1 shows a pre-procedure magnetic resonance image with gadolinium of the pulmonary veins. This image demonstrated a fifth aberrant pulmonary vein (additional left superior pulmonary vein). The procedure was performed using a double trans-septal technique in which two long sheaths were placed across the interatrial septum into the left atrium. A non-contact mapping catheter was placed through a 10 French sheath into the left atrium (Endocardial Solutions Inc., St. Paul, Minnesota). The patient was heparinized in order to achieve an activated clotting time greater than or equal to 350 seconds. In addition, a 4-mm-tip radiofrequency ablation catheter was also placed across the interatrial septum. Electrograms from the coronary sinus and His-bundle catheters were recorded and standard programmed electrical stimulation with isoproterenol was performed. A left atrial tachycardia was induced at a cycle length of 400 msec (Figure 2). Non-contact mapping identified the origin of tachycardia at the right superior pulmonary vein ostium (Figure 3). Figure 4 shows fluoroscopic images of the ablation catheter at the site identified as the origin of the tachycardia and the non-contact “balloon” catheter inside the left atrium. Seventeen short and discreet radiofrequency applications at 40 watts at 60 degrees centrigrade using a 4-mm-tip steerable ablation catheter were delivered to that site using limited fluroscopy during the applications. At the end of the procedure, programmed electrical stimulation failed to induce any tachycardia; at follow-up, there was no evidence of recurrence. Discussion. For many years, mapping of atrial tachycardias involved point-by-point mapping of activation times. In recent years, other techniques including the deployment of a basket catheter have been useful in ablating ectopic atrial tachycardias.^1,2 More recently, a contact electroanatomic mapping system has also been employed.³ The CARTO (Biosense Webster Inc., Diamond Bar, California) mapping system allows a three-dimensional color-coded electroanatomic map of impulse propagation that helps in localization of the origin of the atrial tachycardias.⁴ However, with CARTO, a stable sustained arrhythmia is required in order to identify the earliest activation sequence.⁵ The non-contact mapping systems used in this study is capable of collecting thousands of data points in a single heartbeat without the need for point-by-point mapping. A high-resolution “non-contact” mapping system capable of single-beat mapping has been validated in humans.^5–7 In this paper, we describe the utility of a non-contact three-dimensional mapping catheter and system in helping to localize an ectopic atrial tachycardia. The EnSite 3000 catheter (Endocardial Solutions Inc., St. Paul, Minnesota) uses a multielectrode array comprising a braid of 64 electrodes in a balloon configuration. This balloon is deployed and positioned in the left atrium via a trans-septal technique. By reconstructing and interpolating more than 3,000 unipolar endocardial electrograms, this system delineates the geometry of the left atrium. After a short atrial tachycardia and a single atrial premature contraction, we were able to localize the precise focus causing the arrhythmia. In summary, this paper describes the utility of a three-dimensional non-contact mapping method for ablating an ectopic left atrial tachycardia This approach can be applied to other tachycardias including ventricular tachycardia,^8,9 atrial flutter,¹⁰ and atrial fibrillation ablation (pulmonary vein isolation).^11,12Acknowledgment. We greatly appreciate the assistance of Zhong Wang, PhD, from Endocardial Solutions Inc., who helped provide technical analysis during this case.