This unusual tracing may be observed when the SecureSense™ algorithm is programmed, with different sensing circuits on the 2 channels. In presence of premature ventricular contractions, the noise counter should be reset to 0 each time 2 short cycles have been detected on the discrimination channel. Some sensing delay of the signals may be present, however, between the 2 channels, which may cause a difference of classification, since a cycle may be considered short on the bipolar channel (increment of the noise counter), however long on the discrimination channel (no resetting to 0 of the counter). In this patient, the slower zone of tachycardia was programmed at 420 ms. A bigeminy and a coupling of the premature ventricular contraction were close to that slow zone limit (between 390 and 430 ms) with a (-) marker corresponding to a short cycle when the instantaneous interval was shorter than 420 ms. The limit defining a short cycle on the discrimination channel is 450 ms (420 + 30). The interpretation of the algorithm function is complicated by the absence of indication of instantaneous intervals on the discrimination channel and by presence of a single VS² marker, which does not allow the differentiation of short from long cycles. The sinus QRS complex is sensed first on the discrimination channel, with a prominent delay on the bipolar channel due to the right bundle branch block (delayed activation of the right ventricle, which contains the lead). Conversely, the premature ventricular contractions originate from the right ventricle and are sensed early on the bipolar channel, and later, on the discrimination channel, with also a difference of a few dozens of ms. Ultimately, the difference in the timing of the sensing of these 2 signals explains that the cycles are classified as short (<420 ms) on the bipolar channel and long (>450 ms) on the discrimination channel leading to the recording of an episode classified false positively as oversensing by the device.