Bracketing of premature beats arising from the left bundle branch.

Fascicular premature ventricular contractions (PVCs) can arise from anywhere in the His Purkinje system, but PVCs originating from the left bundle branch (LBB) are rarely reported. We report the case of PVC arising from the LBB, and also describe the electrophysiological features that might indicate the bracketing of the fascicular PVC focus.