The activation of the SecureSense™ algorithm makes diagnoses that are sometimes unexpected as, in this case, the intermittent loss of RV capture. In this patient, the programmed amplitude of stimulation was too low, at the limit of threshold and without safety margin. With each loss of capture, a SecureSense™ alert was recorded. The delay between the ineffective ventricular stimulus and the sensing of spontaneous conducted activation was longer than the post-pacing ventricular blanking period and was expressed by the detection of a short cycle on the bipolar channel. Conversely, the spontaneous ventricular event was the only event sensed on the discrimination channel, explaining the absence of short cycle (no ventricular depolarization after the ventricular stimulus). An adapted programming of the stimulation amplitude solved the problem.