Related Experiment Videos
Virtual electrode effects in myocardial fibers
S B Knisley1, B C Hill, R E Ideker
1Department of Biomedical Engineering, School of Engineering, Duke University, Durham, North Carolina 27710.
Biophysical Journal
|March 1, 1994
Summary
Unipolar cardiac stimulation creates virtual electrode effects, altering transmembrane potential beyond 1 mm. Stronger stimuli significantly influence myocardial electrical behavior, impacting heart function.
Area of Science:
- Cardiovascular Physiology
- Biophysics
Background:
- Transmembrane potential changes during cardiac stimulation are not fully understood.
- Accurate measurement is crucial for understanding cardiac electrical activity.
Purpose of the Study:
- To investigate transmembrane potential changes during cardiac stimulation.
- To elucidate the role of virtual electrode effects in myocardial excitation.
Main Methods:
- Utilized transmembrane potential-sensitive dye fluorescence.
- Measured potential changes along anisotropic rabbit epicardial fibers.
- Employed extracellular point and line stimulation (cathodal and anodal).
Main Results:
- Virtual electrode effects observed beyond 1 mm from stimulation points.
- Cathodal stimulation induced negative potential changes, anodal stimulation reversed polarity.
- Strong stimulation (50-ms pulse, 20-volt) caused significant potential shifts, comparable to action potential amplitude.
- Anodal stimulation during diastole could initiate and accelerate excitation.
Conclusions:
- Unipolar cardiac stimulation generates significant virtual electrode effects in myocardial fibers.
- These effects can substantially influence the overall electrical behavior of the myocardium, especially at higher stimulus strengths.