In order to determine if all changes considered here to model congestive heart failure were necessary to induce VF, we repeated the rapid pacing simulations with two accelerated beats for three additional models: 1) a model with only the membrane changes at the cell level; 2) a model with only modified calcium handling at the cell level; and 3) a model with no Connexin 43 alteration, i.e., normal conduction velocity. The gene discussed is GJA1; the disease is congestive heart failure.