Remodelling of action potential and intracellular calcium cycling dynamics during subacute myocardial infarction promotes ventricular arrhythmias in Langendorff-perfused rabbit hearts.
We hypothesize that remodelling of action potential and intracellular calcium (Ca(i)) dynamics in the peri-infarct zone contributes to ventricular arrhythmogenesis in the postmyocardial infarction setting. To test this hypothesis, we performed simultaneous optical mapping of Ca(i) and membrane potential (V(m)) in the left ventricle in 15 rabbit hearts with myocardial infarction for 1 week. Ventricular premature beats frequently originated from the peri-infarct zone, and 37% showed elevation of Ca(i) prior to V(m) depolarization, suggesting reverse excitation-contraction coupling as their aetiology. During electrically induced ventricular fibrillation, the highest dominant frequency was in the peri-infarct zone in 61 of 70 episodes. The site of highest dominant frequency had steeper action potential duration restitution and was more susceptible to pacing-induced Ca(i) alternans than sites remote from infarct. Wavebreaks during ventricular fibrillation tended to occur at sites of persistently elevated Ca(i). Infusion of propranolol flattened action potential duration restitution, reduced wavebreaks and converted ventricular fibrillation to ventricular tachycardia. We conclude that in the subacute phase of myocardial infarction, the peri-infarct zone exhibits regions with steep action potential duration restitution slope and unstable Ca(i) dynamics. These changes may promote ventricular extrasystoles and increase the incidence of wavebreaks during ventricular fibrillation. Whereas increased tissue heterogeneity after subacute myocardial infarction creates a highly arrhythmogenic substrate, dynamic action potential and Ca(i) cycling remodelling also contribute to the initiation and maintenance of ventricular fibrillation in this setting.
Chou
Chung-Chuan
CC
Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA.
Zhou
Shengmei
S
Hayashi
Hideki
H
Nihei
Motoki
M
Liu
Yen-Bin
YB
Wen
Ming-Shien
MS
Yeh
San-Jou
SJ
Fishbein
Michael C
MC
Weiss
James N
JN
Lin
Shien-Fong
SF
Wu
Delon
D
Chen
Peng-Sheng
PS
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001145:Arrhythmias, Cardiac / Q000209:etiology*; D002118:Calcium / Q000378:metabolism*; D005117:Cardiac Complexes, Premature / Q000209:etiology; D002304:Cardiac Pacing, Artificial; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D006352:Heart Ventricles; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D008564:Membrane Potentials; D009203:Myocardial Infarction / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology*; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D011930:Reaction Time / Q000187:drug effects; D017180:Tachycardia, Ventricular / Q000209:etiology; D014693:Ventricular Fibrillation / Q000209:etiology / Q000503:physiopathology
D000889:Anti-Arrhythmia Agents; D011433:Propranolol; D002118:Calcium