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Figure 1 Stored EGM from the Cadence ICD in a control subject. The EGM is recorded at 256 Hz from a bipolar sensing lead in the right ventricle. The time, in seconds, is displayed at the bottom of the strip. The sharp signals, lasting 100 ms, represent ventricular depolarization. This EGM initially depicts a rhythm, consistent with atrial fibrillation (A). The rhythm spontaneously converts into a more rapid rhythm (B), which meets detection criteria for VT, and antitachycardia pacing is delivered (C) in an attempt to terminate the rhythm. This intervention causes an acceleration of the arrhythmia (D), and a shock is delivered (E), with the resultant termination of the tachyarrhythmia (F) and resumption of a slower rhythm, consistent with sinus rhythm.