A, left, sustained AF/AT is re-inducible during flecainide but not during chloroquine perfusion. Right, after washout sustained AF/AT is re-inducible in both groups. B, representative traces; rapid pacing at 12 Hz did not capture or re-induce non-sustained AF during chloroquine (top); at the same pacing frequency, sustained AF was readily induced during flecainide (bottom). C, time-course of DFmax, SR is restored when chloroquine was perfused after flecainide washout.