Line Stimulation Parallel to Myofibers Enhances Regional Uniformity of Transmembrane Voltage Changes in Rabbit Hearts
| Autor: | S B, Knisley, T C, Baynham |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Membrane potential
Materials science Physiology Transmembrane voltage Muscle Fibers Skeletal Action Potentials Heart Pyridinium Compounds Stimulation Anatomy Models Biological Electric Stimulation Line (electrical engineering) Dispersion (optics) Electrode Biophysics Animals Computer Simulation Rabbits Fiber Cardiology and Cardiovascular Medicine Ion channel Fluorescent Dyes |
| Zdroj: | Circulation Research. 81:229-241 |
| ISSN: | 1524-4571 0009-7330 |
| DOI: | 10.1161/01.res.81.2.229 |
| Popis: | Abstract The sign of transmembrane voltage (V m ) change (ΔV m ) in the heart during unipolar point stimulation is nonuniform, which introduces dispersion of states of V m -dependent ion channels that depends on fiber orientation. We hypothesized that line stimulation parallel to cardiac fibers increases regional uniformity of the ΔV m sign. To test this, we evaluated electrode current distribution and ΔV m produced by unipolar line stimulation in isolated rabbit hearts. The V m -sensitive fluorescent dye, di-4-ANEPPS, and a laser scanner provided ΔV m measurements at 63 spots in an 8×8-mm epicardial region. Line stimulation was tested at specific angles with respect to the fiber direction. Current peaks occurred at electrode ends. For electrodes parallel to fibers (0°), epicardium in regions beyond the ends exhibited a nonuniform ΔV m sign, whereas epicardium between the ends exhibited a uniform ΔV m sign that was essentially negative (hyperpolarized) during anodal pulses and positive (depolarized) during cathodal pulses. The ΔV m sign between the ends became less uniform when the stimulation angle was increased relative to the long axis of the fibers. At 90°, the ΔV m sign between the ends was nonuniform and was frequently opposite, near versus away from the electrode. Spatial distributions of ΔV m during line stimulation were qualitatively predictable from anisotropic effects of point stimulation provided that combined effects of points along the electrode and points with higher current near ends were considered. For biphasic line stimulation, ΔV m during the second phase was weakly correlated with the temporal sum of effects of phases given individually, indicating limited ability of summation to predict ΔV m . Thus, uniformity of the ΔV m sign during stimulation is enhanced in the region between the ends of a line electrode parallel to fibers. This may lessen arrhythmogenic dispersion of V m -dependent ion channel states in the region. |
| Databáze: | OpenAIRE |
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