“…For our purposes, we may think of APD as a cell's effective refractory period (ERP) during which no excitations, even strong ones, can elicit new action potentials. The restitution of APD, which can be experimentally measured or derived from ionic models, is the most extensively studied of restitution relations (Banville and Gray, 2002;Cain, 2007;Cain and Schaeffer, 2006;Cain et al, 2004;Cao et al, 1999;Chen et al, 2005;Cherry and Fenton, 2004;Cytrynbaum and Keener, 2002;Gilmour et al, 1999;Hall et al, 1999;Ito and Glass, 1992;Kalb et al, 2004;Koller et al, 1998Koller et al, , 2005Mitchell and Schaeffer, 2003;Nolasco and Dahlen, 1968;Qu et al, 1997;Sedaghat et al, 2005;Stubna et al, 2002;Ten Tusscher et al, 2006;Vinet, 2000;Watanabe et al, 2001;Watanabe and Koller, 2002). Any APD restitution function, whether experimentally measured or analytically derived can be used in this model.…”