  We study the drift of spiral waves in a simple model of heterogeneous
excitable medium, having gradients in local excitability or cellular coupling.
For the first time, we report the anomalous drift of spiral waves towards
regions having higher excitability, in contrast to all earlier observations in
reaction-diffusion models of excitable media. Such anomalous drift can promote
the onset of complex spatio-temporal patterns, e.g., those responsible for
life-threatening arrhythmias in the heart.
