Control of Spatio-temporal Chaos in the Heart
Spatiotemporally chaotic wave dynamics underlie a variety of debilitating crises in extended excitable systems including the heart. Current strategies for controlling these dynamics employ global, largeamplitude perturbations acting indiscriminately on the system as a whole. For example, the automated external defibrillator commonly found in airports gives via two electrodes a high-energy (1000 V, 30 A, 12 ms) electric shock to terminate the chaotic and ultimately lethal wave dynamics underlying ventricular fibrillation. The adverse effects of such large shocks have motivated a search for less harmful strategies. It is well known that control of spatiotemporal chaos requires multiple control sites. Creating such sites in living tissue, however, is a long-standing problem.
We have shown that natural anatomical heterogeneities within cardiac tissue can provide a large and adjustable number of control sites for low-energy termination of malignant wave dynamics. This allows us to terminate ventricular fibrillation in canine cardiac tissue using small amplitude pulsed electric fields with up to two orders of magnitude lower energies than those used for defibrillating shocks. We quantify the physical mechanism underlying the creation of control sites using fully time resolved high-spatial resolution imaging of wave emission and high-resolution magnetic resonance imaging of cardiac structure. Our method avoids the invasive implantation of multiple electrodes and, more importantly, has the potential to control the tissue where the chaotic state is most susceptible, i.e., at rotating wave cores. This approach promises to significantly enhance current technologies for the termination of life-threatening cardiac arrhythmias, a leading cause of mortality and morbidity in the industrialized world. For this innovation, we have received the Innovationspreis Medizintechnik 2008 (Medical Technology Innovation Award 2008) from the German Ministry for Education and Research (BMBF).