Files in this Data Supplement:

• Figure IA and IB - (TIF) (261 KB) RAO radiographs of coronary venous mapping. (A) Occlusive venogram demonstrating the coronary sinus and proximal GCV. There is a small marginal vein with a takeoff from the proximal GCV (small arrow). (B) Multipolar microcatheters in the GCV (large arrows) and marginal branch (small arrows).
• Figure IC - (TIF) (153 KB) 6F 4 mm electrode catheter positioned in the proximal portion of the marginal branch at the site of successful VT ablation (small arrow).
• Figure IIA and IIB - (TIF) (123 KB) Surface ECG and intracardiac electrograms from the same patient as figure 3. (A) The left half of the panel demonstrates the 12 lead ECG during tachycardia. Note the slight irregularity of cycle length. Pacing from the ablation site (right half of panel) results in an exact match of QRS morphology in all 12 leads. (B) Recordings from the distal bipole of the ablation (A) catheter (arrow) and bipolar pairs of the venous epicardial mapping catheter (E) in the GCV. Activation at this site is 53 ms prior to QRS onset.
• Figure IIC - (TIF) (74.1 KB) Termination of VT within 2 sec after onset of radiofrequency energy application of 5 watts and a temperature of 60°C.
• Figure III - (TIF) (72.5 KB) Surface and intracardiac electrograms from a patient with unsuccessful transpericardial ablation of a tachycardia arising adjacent to the proximal AIV. Recordings from the distal electrodes of the epicardial venous mapping catheter (E1-2, E2-3) demonstrate a sharp high frequency potential 45 ms prior to QRS onset (arrow). Recordings from the transpericardial irrigated ablation catheter (A1-2) positioned over these electrodes demonstrate only a low frequency potential with onset 15 ms after the onset of the high frequency venous signal.
• Figure IV - (TIF) (42.9 KB) Graph illustrating the distribution of V2 MDI values in various subgroups of patients with idiopathic VT. There is greater overlap between groups. ROC analysis demonstrated that a V2MDI of >0.58 had a sensitivity of 100% and specificity of 85.5% in detecting VT of epicardial origin.