ABSTRACT
Controlling spiral waves using low-amplitude external perturbation is not only a problem of fundamental interest in the study of dynamics of excitations in active media [Ho¨rning et al. 2009; Isomura et al. 2008; Sinha and Sridhar 2008; Sinha et al. 2001; Sridhar and Sinha 2008; Takagi et al. 2004; Zhang et al. 2005a], but also has significant implications for the clinical treatment of cardiac arrhythmias [Fenton et al. 2009]. A potentially fatal arrhythmia occurring in the ventricles is tachycardia, or abnormally fast excitation, during which the heart can be activated as rapidly as 300 beats per minute. There are multiple mechanisms by which ventricular tachycardia (VT) may arise, but the most common one is due to the formation of a reentrant pathway, i.e., a closed path of excitation feedback. Reentry often has an anatomical substrate, with the excitation wave going round and round an existing inexcitable obstacle, e.g., a region of scar tissue as shown in Fig. 11.1 (left).
