title: Catheter ablation of ventricular fibrillation in rabbit ventricles treated with beta-blockers.
abstract: BACKGROUND
  A therapeutic implication of the focal-source hypothesis of ventricular fibrillation (VF) is that VF can be terminated by focal ablation. We hypothesize that beta-adrenergic receptor blockade converts multiple-wavelet VF to focal-source VF and that this focal source is located near the papillary muscle (PM).
  
  
  RESULTS
  We used optical mapping techniques to study the effects of propranolol (0.3 mg/L) on VF dynamics in Langendorff-perfused rabbit hearts. The left ventricular (LV) anterior wall was mapped and optical action potential duration restitution (APDR) was determined at 25 epicardial sites. We performed ablation during VF of the left anterior PM in hearts with (N=6) or without (N=6) cytochalasin infusion, the LV lateral epicardium (Epi group, N=3), and the LV endocardium (Endo group, N=3). The PM was also ablated in 3 hearts without propranolol (control group). Propranolol converted multiple-wavelet VF to slow VF with reentry localized to the PM. Propranolol decreased the maximal slope of the APDR curve (P<0.001) as well as its spatial heterogeneity (P<0.01) and conduction velocity (P=0.01) while increasing the VF cycle length (P<0.001). PM ablation terminated VF during propropranolol infusion with (6 of 6, 100%) or without (4 of 6, 67%) cytochalasin D and significantly reduced inducibility. VF did not terminate in the Epi, Endo, and control groups (P<0.001).
  
  
  CONCLUSIONS
  Propranolol flattens the APDR curve and reduces conduction velocity, converting multiple-wavelet VF into VF with a focal source anchored to the PM. Ablation of this focal source may terminate VF.
authors.affiliation: Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center and David Geffen School of Medicine, University of California Los Angeles, Calif 90048, USA.
authors.forename: Hui-Nam
authors.initials: HN
authors.lastname: Pak
authors.forename: Yong-Seog
authors.initials: YS
authors.lastname: Oh
authors.forename: Yen-Bin
authors.initials: YB
authors.lastname: Liu
authors.forename: Tsu-Juey
authors.initials: TJ
authors.lastname: Wu
authors.forename: Hrayr S
authors.initials: HS
authors.lastname: Karagueuzian
authors.forename: Shien-Fong
authors.initials: SF
authors.lastname: Lin
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000818:Animals; D018780:Body Surface Potential Mapping; D017115:Catheter Ablation; D003131:Combined Modality Therapy; D015638:Cytochalasin D / Q000494:pharmacology; D006352:Heart Ventricles / Q000503:physiopathology / Q000601:surgery; D010210:Papillary Muscles / Q000601:surgery; D011433:Propranolol / Q000627:therapeutic use*; D011817:Rabbits; D014693:Ventricular Fibrillation / Q000188:drug therapy* / Q000503:physiopathology / Q000601:surgery*
chemical_list: D000319:Adrenergic beta-Antagonists; D015638:Cytochalasin D; D011433:Propranolol