is somewhat arbitrary the operator can choose any number and thus select a reasonable compromise between patient convenience and noise rejection fig1 shows the possible effect of a biasing current pulse at the qrs onset 32 all of the changes shown in fig9 are still possible but are left off of this figure for clarity another effect is emphasized here which is slightly different in principal from the directly stimulated early potentials the stimulation of the biasing current pulse may not have been strong enough on its own to have caused the unstable cells to fire as was shown in fig9 however the earlier partial 34 subthreshold 34 stimulation may increase the sensitivity of a cell so that it fires earlier in the cardiac cycle than it normally would an increase in sensitivity of a neurological cell due to a shortly earlier subthreshold stimulation is called a wedensky facilitation the wedensky facilitation may cause an unstable cell that was normally triggered by the electrical wave going through the heart to fire while the wave is some distance away because of the increased sensitivity if there were any unstable cells this would cause a shift of some of the energy of the qrs complex towards the first stages this would cause a distortion in the early part of the qrs 33 with a compensatory and opposite distortion in a later region 34 a similar effect can occur in the t wave this figure also shows a distortion in the early part of the t wave 35 with a compensatory and opposite distortion in a later region 36 refer now to fig1 the wedensky facilitation last for about 50 msec after the subthreshold stimulation pulse.