Topological analysis of experimental recordings of ventricular fibrillation

Spiral wave breakup caused by dispersion of tissue refractoriness has long been believed to maintain complex cardiac rhythms such as atrial and ventricular fibrillation. To test this hypothesis, we have developed a level-set based method to reliably extract temporally and spatially resolved positions of wavefronts, wavebacks, and phase singularities from noisy optical mapping data. The utility of this method was illustrated by analyzing optical mapping voltage data during ventricular fibrillation in a Langendorff-perfused pig heart. A recent topological analysis of a 2D model of atrial tissue has shown that four distinct mechanisms increase the complexity of the excitation pattern and two distinct mechanisms decrease its complexity. This analysis predicted that wave coalescence plays the key role in maintaining fibrillation. A similar topological analysis of our experimental recordings supports this theoretical prediction in ventricular tissue as well, which is essentially 3D.