The invention provides a method of recovering from de-synchronization attacks includes registering original and altered digital content using nonlinear transformations to iteratively attempt to provide better-approximated registration. More specifically, an ablation lesion is formed which electrically isolates the located source of the atrial premature contraction in the pulmonary vein from connection with the left atrium and blocks passage of the atrial premature contraction originating from the located source. The external peripheral surface of the end cap is knurled so as to facilitate the manual removal of the end cap without the need for special tools, and most importantly, the dispensing tip portion of the dispensing nozzle is axially recessed with respect to the front surface of the end cap so as not to comprise a readily externally accessible surface portion.