Dynamics of abnormal pacemaking activity in cardiac Purkinje fibers.

A model of the electrical activity in mammalian cardiac Purkinje fiber is examined to study the effects of subcellular oscillations on the transmembrane potential. Inhibition of the sodium/potassium pump causes oscillations in the internal calcium concentration and these oscillations are shown to interfere with the normal pacemaking mechanism of the Purkinje fiber. Bifurcation diagrams were constructed using numerical continuation methods. These results predict a dramatic change in the structure of periodic orbits of the cell electrical activity with pump inhibition and elevated levels of internal sodium concentration.