Catheter ablation in patients with multiple and unstable ventricular tachycardias after myocardial infarction - Short ablation lines guided by reentry circuit isthmuses and sinus rhythm mapping

Background-Extensive lines of radiofrequency (RF) lesions through infarct ( MI) can ablate multiple and unstable ventricular tachycardias (VTs). Methods for guiding ablation that minimize unnecessary RF applications are needed. This study assesses the feasibility of guiding RF line placement by mapping to identify a reentry circuit isthmus. Methods and Results-Cathete r mapping and ablation were performed in 40 patients (MI location: inferior , 28; anterior, 7; and both, 5) with an electroanatomic mapping system to m easure the infarct region and ablation lines. The initial line was placed i n the MI region either through a circuit isthmus identified from entrainmen t mapping or a target identified from pace mapping. A total of 143 VTs (42 stable, 101 unstable) were induced. An isthmus was identified in 25 patient s (63%; 5 with only stable VTs, 5 with only unstable VTs, and 15 with both VTs). Inducible VTs were abolished or modified in 100% of patients when the RF line included an isthmus compared with 53% when RF had to be guided by pace mapping (P=0.0002); those with an isthmus identified received shorter ablation lines (4.9 +/-2.4 versus 7.4 +/-4.3 cm total length, P=0.02). Duri ng follow-up, spontaneous VT decreased markedly regardless of whether an is thmus was identified. VT stability and number of morphologies did not influ ence outcome. Conclusions-A 4- to 5-cm line of RF lesions abolishes all inducible VTs in more than 50% of patients. Less ablation is required if a reentry circuit i sthmus is identified even when multiple and unstable VTs are present.