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Figure 2 Patient 22. Initiation of both AV reentrant beat and sustained AV reentrant tachycardia following the administration of 30 mg ATP in a patient with a concealed left free wall AP and electrophysiologic evidence of antegrade dual AV node physiology. The AV reentrant echo beat occurs 16 s after the ATP bolus during stable sinus rhythm (740 ms) while AV reentrant tachycardia triggered by atrial premature beats occurs 6 s later. Note that a PR jump of 80 ms is present on the beat associated with the AV reentrant echo beat.