Click on image to view larger version.

Figure 2 Recordings from the distal poles of the mapping catheter (Map) positioned at a posteroseptal left ventricular site where a Purkinje potential preceded the QRS complex by 20 ms during sinus rhythm (A) and by 35 ms during ventricular tachycardia (VT) (B). Pacing during VT at this site demonstrates concealed entrainment with a stimulus-QRS interval of 35 ms (C). The stimulus-QRS interval during pacing matches the Purkinje potential-QRS interval during VT.