Figure 8.

Evolution of the transmembrane potential with dofetilide at a concentration of 30x. Snapshots are taken at the beginning of the QRS complex at 50 ms, at the end of depolarization at 100 ms, and at selected points within the simulation window of 5,000 ms. During the first 100 ms, the Purkinje network drives the excitation from apex to base with a sharp depolarization front propagating across the heart, almost identical to the baseline case without drugs. After a markedly prolonged QT interval, the global excitation disappears. Excitation is no longer driven by the Purkinje network, but by numerous small re-entrant waves that flicker around the heart and excite it in chaotic patterns. The heart is largely frozen at the neutral state at a transmembrane potential of zero with several local self-oscillatory regions.