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B-PO01-108 ATRIAL TACHYCARDIA ABLATION AT THE PULMONIC VALVE IN A PATIENT WITH CONGENITALLY CORRECTED TRANSPOSITION OF GREAT ARTERIES

      Background

      Patients with congenitally-corrected transposition of great arteries (ccTGA) have anatomical differences with clinical ramifications for catheter ablation.

      Objective

      To review the relevant anatomical structures in patients with ccTGA for atrial tachycardia (AT) ablation.

      Methods

      N/A

      Results

      A 50 year old man with ccTGA with palpitations, refractory to medical management, presented for catheter ablation. Baseline ECG demonstrated AT with biphasic narrow P-waves in V1, suggestive of a para-Hisian origin.
      During electrophysiologic study, overdrive pacing at various cycle lengths yielded a fixed return cycle length favoring a micro-reentrant tachycardia. Right and left atrial mapping demonstrated early activation along the right atrial (RA) septum, 40 msec preceding the surface P-wave. Ablation at this site resulted in 2:1 exit block, with subsequent return of AT.
      Mapping of the mitral annulus and pulmonic outflow tract delineated the His-Purkinje system (Figure). Using intracardiac echocardiography, the pulmonic valve was visualized directly opposite to the earliest activation site in the RA (pulmonic and aortic valve locations are reversed in ccTGA). Mapping inside the pulmonic valve demonstrated a double-potential preceding the surface P-wave by 120 msec. Ablation resulted in immediate termination of AT, with no recurrence despite aggressive programmed stimulation, burst pacing, and isoproterenol infusion.

      Conclusion

      We demonstrated the anatomic mapping and ablation of incessant AT in a patient with ccTGA. It is important to appreciate the anatomic relationship between the RA, pulmonic outflow tract, and conduction system to avoid inadvertent injury.
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