title: Relationship of bipolar and unipolar electrogram voltage to scar transmurality and composition derived by magnetic resonance imaging in patients with nonischemic cardiomyopathy undergoing VT ablation.
abstract: BACKGROUND
  Bipolar voltage mapping has a role in defining endocardial-based scar in postinfarct patients undergoing ventricular tachycardia catheter ablation. The utility of bipolar and unipolar voltages in characterizing scar has not been evaluated in patients with nonischemic cardiomyopathy.
  
  
  OBJECTIVE
  To relate left ventricular (LV) endocardial bipolar and unipolar voltages in these patients to scar transmurality (endocardial vs nonendocardial) and composition (homogeneous core vs heterogeneous gray).
  
  
  METHODS
  Ten consecutive cardiomyopathy patients undergoing endocardial LV tachycardia ablation were included (age 48 ± 14 years; left ventricular ejection fraction 43% ± 15%). Preablation late gadolinium-enhanced magnetic resonance imaging was used to quantify core and gray scar by using signal-intensity thresholding. Electroanatomic LV endocardial mapping provided bipolar and unipolar voltages. Electroanatomic maps and late gadolinium-enhanced magnetic resonance imaging were rigidly registered in order to relate voltage to scar (registration error 3.6 ± 2.9 mm).
  
  
  RESULTS
  Bipolar voltage was lower in endocardial core than in no scar (P <.001). Unipolar voltage was lower in endocardial core and nonendocardial core than in no scar (P <.001). Endocardial and nonendocardial gray scar had an effect similar to that of core in reducing bipolar and unipolar voltages (P <.001). The mass of healthy myocardium and endocardial core scar independently predicted bipolar and unipolar voltages using general estimating equation modeling. With receiver operating characteristic curve analysis, bipolar voltage >1.9 mV and unipolar voltage <6.7 mV had a high negative predictive value (91%) for detecting nonendocardial scar from either endocardial scar or no scar.
  
  
  CONCLUSIONS
  In patients with nonischemic cardiomyopathy, LV endocardial bipolar voltage is dependent on endocardial core and gray scar, while the unipolar voltage is influenced by core and gray scar across the LV wall as defined by late gadolinium-enhanced magnetic resonance imaging.
authors: Division of Cardiology, University Health Network, Toronto, Ontario, Canada.
authors: Danna A
authors: DA
authors: Spears
authors: Adrian M
authors: AM
authors: Suszko
authors: Rupin
authors: R
authors: Dalvi
authors: Andrew M
authors: AM
authors: Crean
authors: Joan
authors: J
authors: Ivanov
authors: Kumaraswamy
authors: K
authors: Nanthakumar
authors: Eugene
authors: E
authors: Downar
authors: Vijay S
authors: VS
authors: Chauhan
mesh_terms: D000328:Adult; D000368:Aged; D018780:Body Surface Potential Mapping; D009202:Cardiomyopathies / Q000503:physiopathology* / Q000601:surgery*; D017115:Catheter Ablation; D002921:Cicatrix / Q000503:physiopathology*; D003287:Contrast Media; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery*; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media