Figure 2. Induction of asystole with adenosine and external chest wall stimulation. (A) The electrocardiogram and arterial pressure tracing immediately before induction of adenosine-induced asystole are demonstrated. Arrow a illustrates the temporary external pulse generator spikes, and arrow b is the patient's intrinsic QRS complex, which is not currently electronically paced. After the third QRS complex, the patient became asystolic secondary to the action of adenosine. The external pulse generator continues to inhibit the patient's permanent pacemaker and is thus temporarily asystolic. Although there are no intrinsic paced ventricular beats, the patient continues to have a few escape atrioventricular nodal or ventricular complexes (arrow c). (B) The electrocardiogram and arterial pressure tracing immediately before termination of adenosine-induced asystole. Arrow a indicates the last external pulse generator spike before cessation of external chest wall stimulation. Because the patient's own permanent transvenous pacemaker is no longer being inhibited by the external pulse generator, the permanent pacemaker begins to function to treat the patient's residual adenosine-induced bradycardia (arrow b).