Fig 6.

Phase 2 reentry. Reentrant activity induced by exposure of a canine ventricular epicardial preparation (0.7 cm²) to simulated ischemia. Microelectrode recordings were obtained from four sites as shown in the schematic (upper right). After 35 min of ischemia, the action potential dome develops normally at site 4, but not at sites 1, 2, or 3. The dome then propagates in a clockwise direction re-exciting sites 3, 2, and 1 with progressive delays, thus generating a closely coupled reentrant extrasystole (156 msec) at site 1. In this example of phase 2 reentry, propagation of the dome occurs in a direction opposite to that of phase 0, a mechanism akin to reflection. BCL = 700 msec. (Modified from ref. 61 with permission.)