The "Pain wave": P‑wave oversensing in subcutaneous ICD.

A 46-year old man was implanted with a totally subcutaneous implantable defibrillator, after having a documented episode of cardiac arrest due to idiopathic ventricular fibrillation. During the 4‑month follow-up, an episode of inappropriate triple counting due to P‑ and T‑wave oversensing was detected. Although preoperative screening, high detection rates, and the INSIGHT(TM) discrimination algorithm have reduced the incidence of oversensing-related implantable cardioverter defibrillator (ICD) shocks, continuous evaluation of appropriate sensing vectors at rest, during positional maneuver, and exercise, seems to be mandatory at each follow-up visit.