title: Endocardial electrogram characteristics of epicardial ventricular arrhythmias.
abstract: BACKGROUND
  While most ventricular arrhythmias (VA) can be ablated successfully using an endocardial (endo) approach, epicardial (epi) mapping and ablation is sometimes required. There may be suggestive clues on the surface electrocardiogram; however, identification of an epi origin of VA with certainty remains problematic.
  
  
  RESULTS
  All patients referred for ablation of ventricular tachycardia or frequent ventricular ectopy from June 2007 to July 2011 were evaluated. Patients with completed endo and epi electroanatomical activation maps of an epi VA were included (n = 10). Bipolar electrograms (EGMs) in the area of earliest endo activation were analyzed and compared to the area of early epi activation. An EGM component was characterized as far field if it was monophasic and there was inability to capture. We identified 3 characteristics from endo mapping that consistently indicated need for epi ablation: (1) Diffusely early activation (>2 cm(2) region of sites with equally earliest activation within 10 milliseconds). (2) Sequence of a far-field EGM followed by a near-field EGM in the region of earliest endo activation. (3) Inability to capture the far-field component of the earliest EGM (stim-QRS < egm-QRS time) or reproduce morphological features of the VA complex with stimulation at the earliest endo site of activation.
  
  
  CONCLUSIONS
  The presence of a diffusely early area of activation and inability to capture a far-field endo EGM indicates that epi ablation may be needed to eliminate a VA.
authors: Section of Cardiac Electrophysiology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
authors: Wendy S
authors: WS
authors: Tzou
authors: Duy T
authors: DT
authors: Nguyen
authors: Ryan G
authors: RG
authors: Aleong
authors: Paul D
authors: PD
authors: Varosy
authors: David F
authors: DF
authors: Katz
authors: Russell R
authors: RR
authors: Heath
authors: Joseph L
authors: JL
authors: Schuller
authors: Christopher M
authors: CM
authors: Lowery
authors: Laurent
authors: L
authors: Lewkowiez
authors: William H
authors: WH
authors: Sauer
mesh_terms: D000328:Adult; D000368:Aged; D004562:Electrocardiography; D004699:Endocardium / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010496:Pericardium / Q000503:physiopathology; D017180:Tachycardia, Ventricular / Q000503:physiopathology* / Q000601:surgery