Background: High pacing frequency or irregular activity due to arrhythmia present complex signals in optical mapping with overlapping of consecutive wave fronts.
Objective: To establish an analytical framework for optical mapping of complex electrical activity enabling automated signal classification while conserving image resolution and avoiding excessive filtering.
Methods: Optical mapping signals from sheep (N=3), pig (N=1) and human (N=1) ventricular preparations were examined. Windows of activation centered on each action potential upstroke were derived using a Hilbert transform. The windowed maximal derivative defined activation time. Clusters of activation points across neighboring pixels and within a conduction delay of 50ms defined individual wave fronts. Corresponding repolarization times were found as the first subsequent recovery of the signal by 80%. Each wave front was classified as either reentrant or non-reentrant by assessing the median incidence of reactivation of the same wave front within the same pixel. Origins of non-reentrant activation were identified as activation minima. Activation trajectories were calculated as the shortest geodesic path throughout the wave path.
Results: Our framework facilitated full mapping of activation time of individual wave fronts during rapid 7 Hz (pig), Purkinje (sheep) and short-coupled S1S2 (sheep) pacing. Corresponding repolarization and action potential duration maps could also be derived. Focal origins of activation were situated at sites of stimulation or Purkinje muscle junctions. Reentry was induced by a cross-field shock-on-T protocol, in sheep. Maps of reactivation of the same wave front showed highest incidence at the reentry core, Wave front trajectory maps showed preferential activation circumnavigating the reentry core. A sustained right ventricular macroreentry involving the moderator band in sheep and human showed the dependence of the circuit on the moderator band. Activation, repolarization and trajectory maps during S1S2S3S4 and wave fronts at VF induction revealed mechanisms of induction.
Conclusion: This comprehensive analytical approach enables thorough characterization of complex optical mapping signals.