Ectopic activity with complex local electrogram originating from VOM is commonly seen in patients with sustained AF. The P wave morphology associated with the ectopic beats from VOM and from the left PVs was similar. The rate of activation at VOM is significantly faster than other atrial and PV sites during AF. These findings show that rapid activation is present in the VOM during sustained AF in human patients.

We conclude that a strong premature stimulus can induce a Ca(i) sinkhole at the entrance of the CCP. Spontaneous Ca(i) elevation in the Ca(i) sinkhole precedes the V(m) depolarization, leading to Ca current-mediated slow propagation in the CCP. The slow propagation allows more time for tissues at the other side of CCP to recover and be excited to complete figure-eight reentry.