title: Characterization of anatomic ventricular tachycardia isthmus pathology after surgical repair of tetralogy of Fallot.
abstract: BACKGROUND
  Although catheter ablation has been used to target the critical isthmuses for re-entrant monomorphic ventricular tachycardia in tetralogy of Fallot, the anatomy and histology of these regions have not been fully characterized. Autopsy hearts with tetralogy of Fallot were evaluated to clarify the pathological substrate.
  
  
  RESULTS
  Twenty-seven hearts with the diagnosis of tetralogy of Fallot were examined. Anatomically defined isthmuses included (1A) ventriculotomy-to-tricuspid annulus, (1B) ventriculotomy-to-ventricular septal defect patch, (2) ventriculotomy-to-pulmonary annulus, (3) pulmonary annulus-to-ventricular septal defect patch, and (4) ventricular septal defect patch-to-tricuspid annulus. Length and wall thickness were measured for all specimens, and light microscopy was performed for those surviving surgery. For subjects≥5 years at death, isthmuses 1A and 1B were present in 88%, isthmus 2 in 25%, isthmus 3 in 94%, and isthmus 4 in 13%. Isthmus 1A had the greatest dimensions (mean length, 3.9±1.08; thickness, 1.5±0.3 cm), isthmus 1B intermediate dimensions (mean length, 2.4±0.8; thickness, 1.1±0.4 cm), and isthmuses 2, 3, and 4 the smallest dimensions (mean length, 1.5±0.5, 1.4±0.8, and 0.6±0.4 cm; thickness, 0.5±0.2, 0.6±0.2, and 0.3±0.04 cm, respectively). Histological examination (n=7) revealed increased fibrosis in anatomic isthmuses relative to nonisthmus controls.
  
  
  CONCLUSIONS
  Consistencies in isthmus dimensions and histology are found among patients with repaired tetralogy of Fallot. Isthmus 1A is associated with the largest morphological dimensions, whereas the nearby newly described isthmus 1B is significantly smaller. Of isthmuses with the smallest dimensions, isthmus 3 is the most common.
authors.affiliation: Department of Pediatric Cardiology, UCLA Medical Center, Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, UCLA Cardiac Arrhythmia Center, UCLA Health System, University of California at Los Angeles, CA; and Department of Pediatric Cardiology, Loma Linda University Medical Center, CA.
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Moore
authors.forename: Atsuko
authors.initials: A
authors.lastname: Seki
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Shannon
authors.forename: Ravi
authors.initials: R
authors.lastname: Mandapati
authors.forename: Roderick
authors.initials: R
authors.lastname: Tung
authors.forename: Michael C
authors.initials: MC
authors.lastname: Fishbein
mesh_terms: D017115:Catheter Ablation; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000473:pathology*; D013771:Tetralogy of Fallot / Q000473:pathology* / Q000601:surgery*; D016896:Treatment Outcome
keywords: catheter ablation; congenital heart disease; isthmus; tachycardia, ventricular; tetralogy of Fallot