Characteristics of electrograms recorded at reentry circuit sites and bystanders during ventricular tachycardia after myocardial infarction

OBJECYIVES The purpose of this study was to determine the relation of isola ted potentials (IPs) recorded during ventricular tachycardia (VT) to reentr y circuit sites identified by entrainment. BACKGROUND Reentry circuits causing VT late after myocardial infarction are complex. Both IPs and entrainment have been useful for identifying success ful ablation sites, but the relation of IPs to the location in the reentry circuit as determined by entrainment has not been completely defined. METHODS Data from catheter mapping of 70 monomorphic VTs in 36 patients wit h prior myocardial infarction were retrospectively analyzed. Entrainment fo llowed by radiofrequency current (RF) ablation was performed at 384 sites. On the basis of entrainment, sites were classified as reentry circuit exit, central-proximal, inner or outer loop sites. Sites outside the circuit wer e divided into remote and adjacent bystanders. RESULTS Isolated potentials were recorded at 50% (51 of 101) of reentry cir cuit exit, central and proximal sites as compared with only 8% (11 of 146, p < 0.001) of inner loop and outer loop sites and only 1.8% (2 of 106) of r emote bystander sites (p < 0.001). CONCLUSIONS Isolated potentials were also present at 45% of adjacent bystan der sites. At central and proximal sites the presence of an IP increased th e incidence of tachycardia termination by RF to 47.5% from 24% (p = 0.05). At exit sites tachycardia termination occurred frequently regardless of the presence or absence of IPs (45% vs. 48%, p = NS). Isolated potentials at e xit, central and proximal sites had a shorter duration at sites where ablat ion terminated VT than at sites without termination (20.9 +/- 9.6 ms vs. 35 .7 +/- 15.3 ms, p < 0.001). Isolated potentials are a useful guide to sites in the central-proximal region of the reentry circuit, but often fail to i dentify exit sites where ablation is successful. Entrainment and analysis o f electrograms provide complementary information during mapping of VT. (C) 1999 by the American College of Cardiology.