Figure 4. Direct access to vortex cores.

a Termination of fibrillation with LEAP. The pseudo ECG is obtained from the optical mapping experiments (see SI). The dominant frequency during AF is f_v=15.0±0.5Hz (see inset in d). The vertical gray lines indicate the times at which 5 LEAP pulses (f_LEAP=11.8Hz, E=1.96 V/cm) were delivered. A single pulse at this field strength did not terminate fibrillation (pseudo ECG below panel A). Following LEAP normal rhythm is resumed. The termination of fibrillation with f_LEAP<f_v was observed in atria (N=3, 5 episodes) and ventricles (N=1, 3 episodes).

b Area activated indicates tissue synchronization during LEAP. Gray lines indicate timing of LEAP pulses.

c Probability distribution of phases θ_j during AF and for the times of strongest synchronization (maximum order parameter r, see legend) after each LEAP pulse (see SI). During AF, broad phase distributions indicate partial coherence (solid and dashed black lines show two representative distributions). LEAP with f_LEAP<f_v induces synchronization and thus termination of AF.

d Probability distribution of dominant frequencies during AF obtained from optical mapping. The dominant frequency map (inset) shows a complex spatial domain structure corresponding to multiple interacting waves (for color code see histogram; f_v=15.0±1.0Hz; f_LEAP=11.8±0.5Hz indicated by a vertical dashed line).

e Spatio-temporal dynamics during AF, LEAP (images taken at the times of maximum area activated after each pulse; see b), and sinus rhythm (movie S8). The grayscale image shows the atrium (see black line in the last image; 70×70 mm²). The last image shows quiescence after AF termination.