Oversensing in integrated bipolar leads
In integrated bipolar leads the distal shock coil serves as the sensing anode. Their architecture is less complex than those of dedicated bipolar leads and they are less prone to T-wave oversensing and anodal stimulation [1, 2]. On the other hand, the large surface area of the sensing anode (which consists of the entire distal shock coil) renders these leads more prone to sensing of short VV intervals [3], P-wave oversensing, P-wave double-counting [2,4], diaphragmatic oversensing [5], or oversensing due to non-physiological electrical signals that are generated during interactions with other intracardiac leads. The large surface area of the high-voltage coil is more likely to touch an abandoned lead than the ring electrode of a true bipolar ICD lead. This mechanical interaction, or lead-chatter, can cause oversensing and inappropriate shocks [6] or, as in this case, inhibition of pacing due to oversensing. A true bipolar ICD lead should therefore be preferred in patients with abandoned ventricular leads.