  We aim to assess the effectiveness of feedback controlled resonant drift
pacing as a method for low energy defibrillation. Antitachycardia pacing is the
only low energy defibrillation approach to have gained clinical significance,
but it is still suboptimal. Low energy defibrillation would avoid adverse side
effects associated with high voltage shocks and allow the application of ICD
therapy where it is not tolerated today. We present results of computer
simulations of a bidomain model of cardiac tissue with human atrial ionic
kinetics. Re-entry was initiated and low energy shocks were applied with the
same period as the re-entry, using feedback to maintain resonance. We
demonstrate that such stimulation can move the core of re-entrant patterns, in
the direction depending on location of electrodes and a time delay in the
feedback. Termination of re-entry is achieved with shock strength one order of
magnitude weaker than in conventional single-shock defibrillation. We conclude
that resonant drift pacing can terminate re-entry at a fraction of the shock
strength currently used for defibrillation and can potentially work where
antitachycardia pacing fails, due to the feedback mechanisms. Success depends
on a number of details which these numerical simulations have uncovered.
\emph{Keywords} Re-entry; Bidomain model; Resonant drift; ICD; Defibrillation;
Antitachycardia pacing; Feedback.
