Mechanisms of differences of the cycle length of excitation spiral waves in atrial and ventricular tissues

Ectopic spiral wave sources--reverberators--were produced in pieces of rabbit atrium and ventricle by an induction of a single properly timed premature impulse. It was found that the cycle length (T) of the ectopic source gradually increased immediately after its appearance in atrial and changed a little bit after its appearance in ventricular tissue. Relationship between changes of T and refractorines of the heart tissues was investigated. The model is proposed which explains these changes of T by the cycle length dependence on the value of fast inward sodium current.