PREFERENTIAL LOCATIONS FOR CRITICAL REENTRY CIRCUIT SITES CAUSING VENTRICULAR-TACHYCARDIA AFTER INFERIOR WALL MYOCARDIAL-INFARCTION

Reentrant VT Post MI. Introduction: For relatively slow monomorphic ve ntricular tachycardia (VT) after myocardial infarction, entrainment ca n be used to identify reentry circuit ''isthmus sites'' (exit sites an d sites proximal to the exit) where radiofrequency (RF) catheter ablat ion has the greatest likelihood of interrupting reentry, Similarities in coronary and ventricular anatomy may cause such sites to form in pr eferential locations, The objective of this study is to determine if t here are preferential locations for reentry circuit isthmus regions in chronic inferior wall infarctions causing VT. Methods and Results: Ca theter mapping and RF catheter ablation was performed in 21 patients w ith an old inferior wall myocardial infarction and VT, The inferior wa ll was divided into 9 anatomic regions: 3 apical, 3 mid, and 3 basal s egments, Of 46 different VTs, an endocardial isthmus site was identifi ed in one or more zones in 28 (61%), with 10 VTs having isthmus sites in two or more adjacent regions, Isthmus zones were found in a basal r egion of the left ventricle in 24 (86%) of 28 VTs, in a mid segment in 9 (32%) VTs, and in an apical segment in 1 (4%) (P = 0.002), Of 30 RF current applications that terminated VT, 21 (70%) were at basal isthm us sites. Conclusion: The high prevalence of endocardial isthmus zones near the base of the left ventricle suggests that the mitral annulus often plays a role in defining the margins of reentry circuits that ca use relatively slow VTs after inferior wall myocardial infarction.