title: Endocardial ablation of postinfarction ventricular tachycardia with nonendocardial exit sites.
abstract: BACKGROUND
  Most infarct-related ventricular tachycardias (VTs) have an exit site that can be targeted by endocardial ablation. However, some VT reentry circuits have an exit site that is intramural or epicardial. Even these circuits may have an endocardial component that can be endocardially ablated.
  
  
  OBJECTIVE
  To assess the prevalence of postinfarction VTs with a nonendocardial exit site that can be successfully eliminated by endocardial ablation.
  
  
  METHODS
  Twenty-eight consecutive patients with postinfarction VT (27 men, age 69 ± 8 years, ejection fraction 0.25% ± 0.15%) were referred for VT ablation. A total of 213 VTs were inducible (cycle length 378 ± 100 ms). Pace mapping was performed throughout the scar, and critical sites were identified for 137 VTs (64.5%). Critical sites identified by entrainment mapping and/or pace mapping were divided into exit and nonexit sites depending on the stimulus-QRS/VT cycle length ratio (S-QRS/VT CL ≤ 0.3 vs>0.3).
  
  
  RESULTS
  Endocardial exit sites (S-QRS/VTCL ≤ 0.3) were identified for 100 of 137 VTs. Only critical nonexit sites were identified for 37 of 137 (27%) VTs. Nonexit sites were confined to a smaller area within the endocardium (1.81 ± 1.7 cm(2)) and were located within dense scar (0.28 ± 0.24 mV) further away from the border zone (2.05 ± 2.79 cm) than did the VT exit sites. Exit sites had a larger area of matching pace maps (3.86 ± 1.9 cm(2); P<.01) and were at a closer distance to the border zone (0.93 ± 1.06 cm; P<.01). A total of 133 of 137 VTs were ablated. The success rate was similar for VTs in which exit sites were targeted (n = 90 of 100) and VTs in which only nonexit sites were targeted (n = 36 of 37) (P = .83).
  
  
  CONCLUSIONS
  In about one-third of postinfarction VTs for which critical sites were identified, the exit site was not endocardial. Critical nonexit sites that are effective for ablation are often within dense scar at a distance from the border zone and can be missed if only the border zone is targeted.
authors: Division of Cardiology, University of Michigan Cardiovascular Center, Ann Arbor, Michigan 48109-5853, USA.
authors: Mohamad C
authors: MC
authors: Sinno
authors: Miki
authors: M
authors: Yokokawa
authors: Eric
authors: E
authors: Good
authors: Hakan
authors: H
authors: Oral
authors: Frank
authors: F
authors: Pelosi
authors: Aman
authors: A
authors: Chugh
authors: Krit
authors: K
authors: Jongnarangsin
authors: Hamid
authors: H
authors: Ghanbari
authors: Rakesh
authors: R
authors: Latchamsetty
authors: Fred
authors: F
authors: Morady
authors: Frank
authors: F
authors: Bogun
mesh_terms: D000368:Aged; D017115:Catheter Ablation / Q000379:methods*; D002921:Cicatrix / Q000473:pathology; D022062:Electrophysiologic Techniques, Cardiac; D004699:Endocardium / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000601:surgery*