Unpinning of spiral waves from rectangular obstacles by stimulated wave trains

Pinned spiral waves are exhibited in many excitable media. In cardiology, lengthened tachycardia correspond to propagating action potential in forms of spiral waves pinned to anatomical obstacles including veins and scares. Thus, elimination such waves is important particularly in medical treatments. We present study of unpinning of a spiral wave by a wave train initiated by periodic stimuli at a given location. The spiral wave is forced to leave the rectangular obstacle when the period of the wave train is shorter than a threshold T_unpin. For small obstacles, T_unpin decreases when the obstacle size is increased. Furthermore, T_unpin depends on the obstacle orientation with respect to the wave train propagation. For large obstacles, T_unpin is independent to the obstacle size. It implies that the orientation of the obstacle plays an important role in the unpinning of the spiral wave, especially for small rectangular obstacles.