Coexistence of two types of ventricular fibrillation during acute regional ischemia in rabbit ventricle.
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.
Liu
Yen-Bin
YB
Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
Pak
Hui-Nam
HN
Lamp
Scott T
ST
Okuyama
Yuji
Y
Hayashi
Hideki
H
Wu
Tsu-Juey
TJ
Weiss
James N
JN
Chen
Peng-Sheng
PS
Lin
Shien-Fong
SF
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*