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.