title: Influence of the skeletal muscle activity on time and frequency domain properties of the body surface ECG during evolving ventricular fibrillation in the pig.
abstract: OBJECTIVE
  To evaluate influence of the skeletal muscle activity (SMA) on time and frequency domain properties of ECG during VF.
  
  
  METHODS
  We studied the first 9min of electrically induced VF (N=7). We recorded Lead II ECG, 247 unipolar epicardial ventricular electrograms (UEGs) and 3 bipolar skeletal electromyograms (EMGs) near the positions of the ECG electrodes (sampling rate, 500Hz). We reconstructed ECG (RECG) from UEGs using forward-solution transformation matrix. Spectral properties of ECG, RECG, UEGs and MEGs were assessed in the range 2-250Hz by the median frequency (MF) and the upper limit of frequency range containing 99% of spectral energy (Flim(99)). Scaling exponent of ECG, RECG and EMGs was calculated in the ranges of 1-8 and 5-20 sampling intervals (ScE1-8 and ScE5-20, respectively).
  
  
  RESULTS
  We observed non-monotonic increases in MF and Flim(99) of the ECG, but not UEGs and RECG, at 1-5min of VF. Maximum values of MF and Flim(99) in ECG, UEGs and RECG were (in Hz): 32+/-29 and 166+/-67; 11+/-2 and 36+/-7; 10+/-2 and 32+/-6, respectively. The transient increases in the high-frequency content of the ECG were correlated with enhanced activity in EMGs, characterized by an almost uniform spectrum in the range 2-250Hz (MF=92+/-29; Flim(99)=245+/-4Hz). Peak values of ScE(1-8) were the highest in EMGs (1.95+/-0.04), intermediate in the ECG (1.59+/-0.26), and the lowest in RECG (1.088+/-0.007).
  
  
  CONCLUSIONS
  SMA significantly contributes to ECG during VF and can bias metrics used for assessment of VF organization.
authors.affiliation: Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, United States. shvedko@cvrti.utah.edu
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Shvedko
authors.forename: Mark D
authors.initials: MD
authors.lastname: Warren
authors.forename: Shibaji
authors.initials: S
authors.lastname: Shome
authors.forename: Jeroen
authors.initials: J
authors.lastname: Stinstra
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Zaitsev
mesh_terms: D000818:Animals; D018780:Body Surface Potential Mapping / Q000379:methods*; D004562:Electrocardiography; D004576:Electromyography; D018482:Muscle, Skeletal / Q000502:physiology*; D013552:Swine; D014693:Ventricular Fibrillation / Q000503:physiopathology*