ABL07: CORRECTION OF OVERSENSING IN A PM-DEPENDENT PATIENT UPGRADED TO CRT-ICD

Exogenous signals can satisfy ICD TV/FV detection criteria and lead to spurious ICD discharges. Moreover, PM-dependent ICD pts can suffer concomitant prolonged pacing inhibition due to suboptimal reliability of noise reversion mode in ICDs. We report a case of oversensing (OS) in a PM-dependent pt upgraded to CRT-ICD.

A pt chronically implanted with a DDD PM because of complete heart block was upgraded to a CRT-ICD device (Contak Renewal 2 H155, Guidant) due to the development of ischemic dilated cardiomyopathy and congestive heart failure. He had his bipolar ventricular PM lead capped and an ICD lead (Endotak Reliance 0148, Guidant) and a CS lead (Easytrak II 4517, Guidant) implanted. At implant the ICD lead was placed as far as possible from the bipolar PM lead,though in vicinity due to a preceding inferior septal infarction. The first postimplant evaluation in ICD clinic, with analysis of real-time and stored intracardiac EGMs, revealed intermittent OS during sinus rhythm, occurring only in the right decubitus position with abducted arm and leading to prolonged inhibition of pacing,with presyncope, and false VF detection, with aborted shocks. OS was demonstrated to result from intermittent physical contact of the distal portions of the active and passive lead in the RV apex. At operative revision, connecting the RV rate-sense port of the ICD to the previously abandoned pacing lead (thus shifting from an integrated bipolar to a true bipolar sensing and reducing the sensing field size) abolished the OS. Subsequent follow-up (22 mos) has been uneventful.field size) abolished the OS. Subsequent follow-up (22 mos) has been uneventful.

The effect of a passive endocardial electrode on sensing specificity of an ICD system in a PM-dependent pt can be potentially catastrophic. In our case OS could be overcome simply reducing the size of the sensing field.