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Updated: Aug 19, 2026
Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
Published on: July 3, 2013
Dissociation of membrane potential and intracellular calcium during ventricular fibrillation
Suhua Wu1, James N Weiss, Chung-Chuan Chou
1Division of Cardiology, Department of Medicine, Cedars-Sinai Medical Center, UCLA, Los Angeles, California 90048, USA.
Insights
The coupling between cardiac action potentials and intracellular calcium transients dissociates during ventricular fibrillation (VF). This dissociation is not caused by the fast activation rates characteristic of VF.
Area of Science:
- Cardiac Electrophysiology
- Cardiovascular Physiology
Background:
- Cardiac action potential (AP) and intracellular Ca transient (CaT) coupling is vital under normal conditions.
- This association is disrupted during ventricular fibrillation (VF).
Purpose of the Study:
- To investigate if the dissociation of AP and CaT during VF is directly related to the rapid activation rates.
- To quantify the degree of AP and CaT coupling during various cardiac rhythms.
Main Methods:
- Simultaneous optical mapping of AP and CaT in isolated rabbit hearts.
- Utilized pinacidil to shorten action potential duration and induce fast pacing and ventricular tachycardia (VT).
- Employed mutual information (MI) to assess AP and CaT coupling.
Main Results:
- Pinacidil significantly shortened action potential duration.
- Mutual information (MI) was higher during fast pacing and VT compared to VF.
- Reduced MI during VF was observed even at rates comparable to fast pacing and VT.
Conclusions:
- Cardiac action potential and CaT coupling is maintained during fast pacing and VT.
- The dissociation between AP and CaT during VF is independent of the fast activation rate.
- Findings suggest other mechanisms underlie the disrupted coupling during VF.
Unlabelled:
Membrane potential and intracellular calcium during VF.
Introduction:
The cardiac action potential (AP) and the intracellular Ca transient (CaT) are closely associated under normal physiological conditions, but not during ventricular fibrillation (VF). The purpose of this study was to determine whether this dissociation is directly related to the fast activation rate during VF.
Methods And Results:
We optically mapped AP and CaT simultaneously in nine isolated rabbit hearts. Pinacidil, a K(ATP) channel opener, was used to shorten the action potential duration (APD) in order to capture tissue at fast pacing rates or to induce ventricular tachycardia (VT) comparable to VF activation rates. Mutual information (MI) was used to calculate the degree of AP and CaT coupling. Pinacidil (40 microM) infusion significantly shortened APD. The CL of VF without pinacidil averaged 77+/-13 ms, whereas the shortest CL achieved during VT under pinacidil infusion was 76 ms. MIs during fast pacing (1.13+/-0.15 bits) and fast VT (0.88+/-0.18 bits) were higher than those during baseline VF (0.39+/-0.11 bits), VF with pinacidil infusion (0.21+/-0.07 bits) and VF after pinacidil washout (0.36+/-0.15 bits). MIs during fast pacing or fast VT were higher than that of VFs at comparable dominant frequencies.
Conclusions:
CaT is closely associated with the AP during fast pacing and fast VT, but not during VF. The reduced MI during VF is not secondary to the fast rate of activation.
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