Emergence of spontaneous rhythm disorders in self-assembled networks of heart cells

A noninvasive optical recording technique is introduced to study the spontaneous contractile activity in self-assembled heart cell networks. Continuous monitoring throughout the lifetime of the network reveals spontaneous appearance of various rhythm disorders. Analysis of two typical patterns, namely, subharmonic structures and sudden alternations between two dominant rates, indicates the emergence of intrinsic pacemakers. A model of one or two slightly variable nonlinear oscillators, acting on an excitable element, is shown to reproduce the main experimental results.