Files in this Data Supplement:

• Movie I - (3.89 MB). Movie I shows the phased-array ICE image of the left isthmus obtained by positioning the echo catheter within the coronary sinus (CS). The echo lucent cavity at the top of the screen is the coronary sinus while the lower cavity is the left atrium (LA) and separating the two is the left isthmus. The 7F externally irrigated ablation catheter (Thermocool, Biosense-Webster, Diamond Bar, Calif) can be seen within the body of the left atrium curved against the left isthmus (between the CS and LA). The movie was recorded 5 seconds after the commencement of left isthmus ablation. Note the marked echo cavitation visible at the ablation catheter tip, which is caused by the open-loop irrigation system (normal saline flow rate 60 mL/min).
• Movie II - (4.15 MB). Movie II is the same view in the same patient after 20 seconds energy delivery (power 40W, 40°C) showing marked edematous tissue reaction with a hypoechoic space within the left isthmus. Echo cavitation is no longer visible at the ablation catheter tip because energy delivery was suspended and the normal saline flow rate was reduced to 2 mL/min.
• Movie III - (2.91 MB). Movie III from a different patient shows the phased-array ICE image of the left isthmus obtained by positioning the echo catheter transseptally into the left atrium. The echo lucent cavity at the top of the screen is the LA, the CS is the echo lucent space at the bottom left, and the LA appendage is seen at bottom right of the screen. The ablation catheter can be seen curving within the LA and across the LA appendage to rest on the left isthmus. This image was obtained after 10 seconds of radiofrequency energy delivery (note that in this case the echo cavitation at the ablation catheter tip is due to an irrigation flow rate of 40 mL/min normal saline). Early edematous tissue reaction can be seen at the ablation site with local tissue thickening.