title: His bundle activates faster than ventricular myocardium during prolonged ventricular fibrillation.
abstract: BACKGROUND
  The Purkinje fiber system has recently been implicated as an important driver of the rapid activation rate during long duration ventricular fibrillation (VF>2 minutes). The goal of this study is to determine whether this activity propagates to or occurs in the proximal specialized conduction system during VF as well.
  
  
  RESULTS
  An 8×8 array with 300 µm spaced electrodes was placed over the His bundles of isolated, perfused rabbit hearts (n = 12). Ventricular myocardial (VM) and His activations were differentiated by calculating Laplacian recordings from unipolar signals. Activation rates of the VM and His bundle were compared and the His bundle conduction velocity was measured during perfused VF followed by 8 minutes of unperfused VF. During perfused VF the average VM activation rate of 11.04 activations/sec was significantly higher than the His bundle activation rate of 6.88 activations/sec (p<0.05). However from 3-8 minutes of unperfused VF the His system activation rate (6.16, 5.53, 5.14, 5.22, 6.00, and 4.62 activations/sec significantly faster than the rate of the VM (4.67, 3.63, 2.94, 2.24, 3.45, and 2.31 activations/sec) (p<0.05). The conduction velocity of the His system immediately decreased to 94% of the sinus rate during perfused VF then gradually decreased to 67% of sinus rhythm conduction at 8 minutes of unperfused VF.
  
  
  CONCLUSIONS
  During prolonged VF the activation rate of the His bundle is faster than that of the VM. This suggests that the proximal conduction system, like the distal Purkinje system, may be an important driver during long duration VF and may be a target for interventional therapy.
authors.affiliation: Comprehensive Arrhythmia Research & Management Center, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT, United States of America; Department of Bioengineering, University of Utah, Salt Lake City, UT, United States of America.
authors.forename: Nathan
authors.initials: N
authors.lastname: Angel
authors.affiliation: Comprehensive Arrhythmia Research & Management Center, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT, United States of America.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: Comprehensive Arrhythmia Research & Management Center, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, UT, United States of America; Department of Bioengineering, University of Utah, Salt Lake City, UT, United States of America; Center for Engineering Innovation, University of Utah, Salt Lake City, UT, United States of America.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Dosdall
mesh_terms: D000818:Animals; D002036:Bundle of His / Q000503:physiopathology*; D006352:Heart Ventricles / Q000473:pathology*; D008297:Male; D009206:Myocardium / Q000473:pathology*; D011690:Purkinje Fibers / Q000503:physiopathology; D011817:Rabbits; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000473:pathology* / Q000503:physiopathology*