Atrial tachycardia arising from the distal left atrial appendage requiring high-power endocardial and epicardial ablation

Figure 1. A: Twelve-lead surface electrocardiogram of atrial tachycardia with P waves negative in leads I and aVL, positive and bifid in inferior leads and lead V1, consistent with a left atrial tachycardia. B: Earliest epicardial activation with ablation signal -65 ms preceding surface P wave. C: Earliest endocardial activation with ablation signal -64 ms preceding surface P wave. Ablation at this site with power of 50 W was successful in terminating tachycardia.

Figure 2. A, B: Right anterior oblique cranial (A) and left lateral cranial (B) view of left atrial endocardial activation map using CARTO (Biosense Webster, Diamond Bar, CA), demonstrating earliest atrial activation in the distal left atrial appendage. C: Left lateral view of epicardial activation map demonstrating a relatively broad area of early activation overlying the distal left atrial appendage. D: Superimposed epicardial and endocardial activation maps demonstrating epicardial surface overlying endocardial geometry of the left atrial appendage. Purple dot marks the site of left phrenic nerve capture.

Figure 3. A: Fluoroscopic image in right anterior oblique view with 7F balloon-tipped Berman catheter (Teleflex Inc, Wayne, PA) placed within the distal left atrial appendage on the endocardial side for applying counter-pressure with the ablation catheter at the site of earliest epicardial activation. B: Successful ablation lesion from endocardial site with power titrated to 50 W with termination of tachycardia at 24.2 seconds. C: CARTOSOUND (Biosense Webster, Diamond Bar, CA) demonstrating ablation catheter at successful endocardial site. The ultrasound probe is in the pericardial space superior and posterior-medial to the left atrial appendage. D: Intrapericardial percutaneous echocardiography image demonstrating ablation catheter tip (yellow arrow) within the distal left atrial appendage. Epicardial ablation lesions indicated with red open circles. Blue circle indicates annotation of an early mapping site on the epicardial side.