title: Coexistence of two types of ventricular fibrillation during acute regional ischemia in rabbit ventricle.
abstract: BACKGROUND
  We previously reported that a normal ventricle can demonstrate two types of ventricular fibrillation (VF), depending on the underlying electrophysiologic characteristics at the time of VF induction. We hypothesize that the two types of VF can coexist in acutely ischemic ventricles.
  
  
  RESULTS
  Optical mapping studies were performed with di-4ANEPPS in 15 Langendorff-perfused rabbit hearts. Coronary artery branches were ligated to create regional ischemia in 10 hearts. Action potential duration measured to 50% repolarization (APD50) during ischemia showed an area with uniformly shortened APD50 (zone 1), an area with normal or lengthened APD50 (zone 3), and an area in between with an APD50 gradient (zone 2). Ischemia flattened APD restitution (APDR) slope and reduced conduction velocity in zone 1, creating a condition for type II VF. APDR steepened and the conduction velocity changed little in the nonischemic zone (zone 3), creating a condition for type I VF. During induced VF, the dominant frequency in zones 2 and 3 progressively increased after ischemia onset. The dominant frequency in zone 1 (ischemic zone) first decreased and then slightly increased but typically remained less than the dominant frequency in zone 3. The number of wavebreaks increased with time in all three zones (baseline: 4.3 +/- 1.5; 30 min: 11.7 +/- 5.6; 60 min: 15.6 +/- 11 per frame; P < 0.01).
  
  
  CONCLUSIONS
  Two types of VF can coexist during acute regional ischemia. Both ischemic and nonischemic regions develop proarrhythmic changes during regional ischemia, thus contributing to increased ventricular vulnerability to VF and sudden death during acute coronary occlusion.
authors.affiliation: Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
authors.forename: Yen-Bin
authors.initials: YB
authors.lastname: Liu
authors.forename: Hui-Nam
authors.initials: HN
authors.lastname: Pak
authors.forename: Scott T
authors.initials: ST
authors.lastname: Lamp
authors.forename: Yuji
authors.initials: Y
authors.lastname: Okuyama
authors.forename: Hideki
authors.initials: H
authors.lastname: Hayashi
authors.forename: Tsu-Juey
authors.initials: TJ
authors.lastname: Wu
authors.forename: James N
authors.initials: JN
authors.lastname: Weiss
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
authors.forename: Shien-Fong
authors.initials: SF
authors.lastname: Lin
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D018780:Body Surface Potential Mapping; D002304:Cardiac Pacing, Artificial; D022062:Electrophysiologic Techniques, Cardiac; D006352:Heart Ventricles / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000503:physiopathology*; D011817:Rabbits; D014693:Ventricular Fibrillation / Q000503:physiopathology*