Figure 6.

Spontaneous initiation of VF in a middle-aged rabbit exposed to 0.1 mM H₂O₂. (A) Six epicardial optical APs (V1–V6) recorded from sites shown on the left silhouette of the heart. After nine focal activations arising from the base of the heart (B), the wavefront undergoes block at mid-LV anterior wall after spatially discordant APD alternans emerges (A). The wavefront, however, continues to propagate lateral to the site of block in a clockwise direction causing a reentrant excitation as shown in the snapshots in (B). The numbers under each snapshot is activation time starting with 0 ms (arbitrary) for beats 3 and 4 and then again for beats 10 and 11. (C) microelectrode recording of another VF episode recorded in the same heart showing spontaneous initiation of VF by a mechanism compatible with early afterdepolarization (EAD)-mediated triggered activity (TA) as in the aged rat hearts shown in Figure 6 (From Morita et al., 2009).