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Inverse relation between input resistance and threshold current in canine cardiac syncytium
1Department of Physiology, Centro de Investigacion y Estudios Avanzados del I. P. N., Mexico City, Mexico. 7530@prodigy.net.mx
Journal of Cardiovascular Electrophysiology
|April 9, 2001
Summary
Differences in input resistance contribute to varied electrical excitability in canine endocardium. This study reveals an inverse relationship between input resistance and the current needed to reach threshold, highlighting cardiac syncytium inhomogeneity.
Area of Science:
- Cardiovascular Physiology
- Cardiac Electrophysiology
Background:
- Cardiac excitability exhibits heterogeneity.
- The role of input resistance in this heterogeneity is not fully understood.
Purpose of the Study:
- To investigate the contribution of input resistance differences to canine endocardial excitability.
- To determine the relationship between input resistance and threshold current in canine cardiac tissue.
Main Methods:
- Experiments utilized isolated canine right anterior papillary muscles.
- Conventional electrophysiological techniques with microelectrodes were employed to measure transmembrane potential and inject current.
- Input resistance and threshold current were determined in single or contiguous cells.
Main Results:
- A strong inverse relationship was found between input resistance and threshold current (R² = 0.97).
- The data fit a rectangular hyperbola model (XY = 30 mV).
- Input resistance varied across different sites of the cardiac preparation.
Conclusions:
- The canine cardiac syncytium is nonhomogeneous regarding input resistance.
- Input resistance is inversely proportional to the minimal current required to reach threshold.
- This inhomogeneity in input resistance leads to inhomogeneous electrical excitability in canine cardiac cells.