Figure 2.

Ventricular fibrillation during the second cardiac arrest, showing beat-to-beat initiation of ventricular fibrillation, followed by a successful ICD discharge. A ventricular escape rhythm follows the successful shock. Four channels are shown. The first channel is a bipolar atrial EGM. The second channel is a bipolar ventricular. The third and fourth channels are atrial and ventricular marker channels respectively, flanked by numbers that show the interval in milliseconds between each marker. The absence of atrial and ventricular EGMs at the beginning of panel A is a normal feature of this manufacturer's ICD system. Ab, atrial blanked event; AP/VP, atrial or ventricular paced event; AR, atrial refractory event; AS/VS, atrial or ventricular sensed event; FS, ventricular sensed event qualifying for the fibrillation counter; 36 J, delivery of a 36 Joule shock.