Fig. 3.

High-resolution 3D activation maps of the culprit PVC in three patients demonstrating earliest activation at the free wall insertion of the MB. a The electrode pair (17,18) records a Purkinje potential fused with local activation during sinus rhythm that is separated from local activation and precedes the QRS onset with a unipolar QS pattern by 20 ms. during short-coupled PVC. The course of the MB—spanning from septum to lateral free wall—can be appreciated by the impressions in the electroanatomic shell of the RV. b Induction of short-coupled PVCs by atrial overdrive pacing. To locate the MB without ICE the earliest activation of the right ventricular free wall in sinus rhythm (right, brown tag) was mapped matching the earliest activation during short-coupled PVC (brown tag in the left picture), confirming the PVC origin to be at the free wall insertion of the MB. After focal ablation at this site short-coupled PVCs were no longer inducible by atrial pacing. c Assuming a RV MB site of origin the MB geometry was created on the electroanatomic mapping system and confirmed by ICE. The earliest activation of the short-coupled PVC was mapped to the free wall insertion of the RV MB, where it was preceded by a prominent Purkinje potential. RF ablation at the site of earliest activation (26 ms pre-QRS) promptly terminated the PVC, and addition ablation was performed at adjacent Purkinje potential sites on the free wall insertion of the MB