Localization of optimal ablation site of idiopathic ventricular tachycardia from right and left ventricular outflow tract by body surface ECG

Background - Idiopathic ventricular tachycardia (VT) is known to arise from the right ventricular (RV) and left ventricular outflow tracts (LVOT). However, reliable noninvasive methods to localize the optimum ablation site for VT have not been reported. Methods and Results - Body surface maps (BSM) and 12-lead ECGs were investigated in 35 VTs from the RVOT and 5 VTs from the LVOT in which the origin was confirmed during the ablation procedure. The RVOT was classified into 8 subdivisions with the use of a 3-dimensional anatomic relation: anterior (A)-posterior (P), right (R)-left (L), and superior (S)-inferior (I). On the BSM, the following 3 indexes differentiated each location of the origin, with a diagnostic accuracy of 88% (A-P), 92% (R-L), and 77% (S-I): (1) the location of the minimum at the early-to-mid QRS (right, A; left, P), (2) the isopotential distribution in the left shoulder area after 30 ms of QRS (positive, R; negative, L), and (3) the downward moving time of the minimum at the early-to-mid QRS (greater than or equal to 50 ms, S; <50 ms, I). On the 12-lead EGG, (1) the QRS duration (>140 ms, A; less than or equal to 140 ms, P) and the R-wave pattern in leads II and III (RR' or Rr', A, R, P), (2) the QS wave amplitude in aVR and aVL (aVR greater than or equal to aVL, R; aVR < aVL, L), and (3) the r-wave amplitude in V-1 and V-2 (high, S; low, I) localized the origin with 80%, 86% (A-P), 80% (R-L), and 66% (S-I) accuracy. R/S greater than or equal to 1 in lead V-3 was an index suggesting the LVOT origin. Conclusions - The origin or the optimum ablation site of idiopathic VT from RVOT and LVOT can be localized with the use of indexes obtained with a BSM or 12-lead EGG.