A method, including acquiring initial signals fromselected positions in a heart, computing respectiveinitial local values of a signal propagation metric atthe selected positions, and interpolating the initiallocal values between the selected positions to computeinitial interpolated values of the signal propagationmetric at intermediate positions, between the selectedpositions. The method further includes acquiringsubsequent signals from the positions, computingrespective subsequent local values of the signalpropagation metric at the selected positions, andspatially interpolating the subsequent local values ofthe signal propagation metric between the selectedpositions to compute subsequent interpolated values ofthe signal propagation metric at the intermediatepositions. A map of the signal propagation metric isdisplayed, and when the subsequent interpolated valuesexceed a bound defined with respect to the initialinterpolated values, an indication is provided on the mapthat the bound has been exceeded.
