title: Regional variation in capture of fibrillating swine left ventricle during electrical stimulation.
abstract: BACKGROUND
  While it has been shown that electrical stimulation can capture a region of myocardium during ventricular fibrillation (VF), the ideal location to stimulate to maximize capture of the fibrillating in vivo left ventricle (LV) is not known. We previously demonstrated a mean directionality to the propagation of VF wavefronts in swine from posterior to anterior LV. We hypothesized that this directionality of VF wavefronts would affect capture of the LV epicardium while stimulating during VF.
  
  
  RESULTS
  In seven open-chest swine, during different VF episodes, electrical stimulation was performed singly or simultaneously from two lines of 26 epicardial electrodes, one on the posterior LV adjacent to the posterior descending coronary artery and another on the anterior LV adjacent to the left anterior descending coronary artery. Mapping was performed between the line of stimulating electrodes with 768 recording electrodes 2-mm apart. The incidence and extent of epicardium captured by stimulation through the lines of stimulating electrodes were determined in the mapped region. Capture occurred during 67% of 78 VF episodes. Capture from the posterior LV line was achieved in 88% of the episodes and from the anterior LV line in 44% of the episodes (P = 0.001). The maximum amount of myocardium captured was also much greater for stimulating from the posterior as compared to the anterior LV line (232 +/- 168 mm(2) vs 64 +/- 124 mm(2), P = 0.003). A significant part of the variability in capture was related to the direction of the mean VF wavefront velocity vector in each animal (r = 0.84, P < 0.05).
  
  
  CONCLUSIONS
  Electrical stimulation from the posterior LV resulted in a greater incidence and extent of LV capture than stimulation from the anterior LV. A significant component of the variability in capture is related to the mean direction of VF wavefronts.
authors.affiliation: Department of Medicine, Division of Cardiovascular Diseases, University of Alabama- Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: Kumaraswamy
authors.initials: K
authors.lastname: Nanthakumar
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Johnson
authors.forename: Jian
authors.initials: J
authors.lastname: Huang
authors.forename: Cheryl R
authors.initials: CR
authors.lastname: Killingsworth
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Rollins
authors.forename: Hugh T
authors.initials: HT
authors.lastname: McElderry
authors.forename: William M
authors.initials: WM
authors.lastname: Smith
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004558:Electric Stimulation; D006339:Heart Rate / Q000502:physiology; D013552:Swine; D018487:Ventricular Dysfunction, Left / Q000503:physiopathology*; D014693:Ventricular Fibrillation / Q000503:physiopathology*