title: Relation of the unipolar low-voltage penumbra surrounding the endocardial low-voltage scar to ventricular tachycardia circuit sites and ablation outcomes in ischemic cardiomyopathy.
abstract: BACKGROUND
  Magnetic resonance (MR)-imaging has shown that infarct scars causing ventricular tachycardia (VT) can extend deep to and beyond bipolar low-voltage areas (LVAs) and may be a source of ablation failure. We hypothesized that the size of the unipolar LVA "penumbra" beyond the overlying bipolar scar may predict outcome of endocardial VT ablation.
  
  
  METHODS
  Twenty consecutive patients with ischemic cardiomyopathy who underwent endocardial VT ablation were retrospectively reviewed. Bipolar (30-500 Hz) LVA defined as <1.5 mV and unipolar (0.5-500 Hz) LVA defined as <8.3 mV were reviewed on an electroanatomic mapping system. VT isthmus sites were identified from entrainment mapping, VT termination by ablation, or pace-mapping with abolition of VT inducibility by ablation.
  
  
  RESULTS
  All bipolar LVAs (70.5 ± 20 cm(2) ) had unipolar LVAs that surrounded the bipolar LVA (147 ± 47 cm(2) ). Only 58% of the induced VTs could be mapped and ablated. During a 3-month follow-up 8/20 patients had VT recurrence. The size of the LVA penumbra was not different for those with (88 ± 47 cm(2) ) versus without (69 ± 35 cm(2) ) recurrences. However, all (8/8) of the group that recurred had isthmus/exits in the bipolar LVA border compared to only 3/12 that did not recur (100% vs. 25%; P < 0.05). Furthermore, 5/8 patients who recurred harbored VT isthmuses in the unipolar LVA penumbra than 1/12 who did not recur (63% vs. 8%; P = 0.01).
  
  
  CONCLUSIONS
  In ischemic cardiomyoapthy, unipolar LVA penumbra of varying size surrounds endocardial bipolar LVA, indicating intramural/epicardial scar. Although the size of this area did not predict early recurrence after endocardial ablation, frequent recurrences after VT ablation at scar periphery suggests deeper substrate toward the infarct border.
authors.affiliation: Arrhythmia Service, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA.
authors.forename: Nagesh
authors.initials: N
authors.lastname: Chopra
authors.forename: Michifumi
authors.initials: M
authors.lastname: Tokuda
authors.forename: Justin
authors.initials: J
authors.lastname: Ng
authors.forename: Tobias
authors.initials: T
authors.lastname: Reichlin
authors.forename: Eyal
authors.initials: E
authors.lastname: Nof
authors.forename: Roy M
authors.initials: RM
authors.lastname: John
authors.forename: Usha B
authors.initials: UB
authors.lastname: Tedrow
authors.forename: William G
authors.initials: WG
authors.lastname: Stevenson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018780:Body Surface Potential Mapping / Q000379:methods*; D009202:Cardiomyopathies / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D017115:Catheter Ablation / Q000379:methods*; D002921:Cicatrix / Q000175:diagnosis* / Q000503:physiopathology; D015331:Cohort Studies; D004699:Endocardium; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D010865:Pilot Projects; D012189:Retrospective Studies; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology; D016896:Treatment Outcome
keywords: ablation; electroanatomic map; ischemic cardiomyopathy; low-voltage area; prognosis; ventricular tachycardia