Mechanism of drift of a helical wave in an inhomogeneous medium

A differential equation is proposed describing the trajectory of drift of a helical wave in inhomogeneous media. For the case of weak inhomogeneity the dependence of the speed of drift on the gradient, radius of the nucleus and the period of rotation of the helical wave has been found. It is shown that in media where the period of rotation is long as compared with the refractory period of the medium drift occurs perpendicular to the gradient of the inhomogeneity. The analytical results are compared with the data of the numerical experiment on a model of the Fitzhugh-Nagumo type.