Patient
- 69-year-old man
- Assurity MRITM pacemaker (Abbott) for paroxysmal atrioventricular block
- AMS episodes in the device memory
Tracing
- oversensing of a very fast, disorganized, non-physiological signal at the level of the atrial lead
- accelerated ventricular pacing before the occurrence of fallback
- fallback to DDIR mode (AMS) with loss of atrioventricular synchrony
Patient
- 61-year-old man
- Assurity MRITM pacemaker (Abbott) for paroxysmal atrioventricular block
- several episodes of HVR in the device memory
Tracing
- oversensing of a very fast, disorganized, non-physiological signal at the level of the ventricular lead inhibiting ventricular pacing
- absence of ventricular pause since the patient is not pacemaker-dependent (intrinsic QRS complexes remain viewable)
Comments
- both of these patients presented an oversensing of myopotentials at the level of the atrial lead (first patient) or ventricular lead (second patient) responsible for multiple episodes of AMS or HVR
- oversensing was reproducible through counter maneuvers
- oversensing of pectoral myopotentials was relatively common in patients implanted with a pacemaker operating in unipolar mode and could result in inhibition of pacing and syncope in pacemaker-dependent patients
- programming of triggered modes (AAT, VVT, DDT) could be proposed in this setting in order to avoid the occurrence of significant pauses
- when sensing is programmed in bipolar mode, given that the can is positioned in the pocket near the pectoral muscles and thus not part of the sensing circuit, the pectoral myopotentials should not therefore induce any oversensing
- in presence of an insulation break (friction between the pulse generator and the lead), the sensing channel can oversense pectoral myopotentials which can cause inhibition of pacing and lead to false diagnoses of VT (HVR) or AF (AMS) depending on the lead
- analysis of the EGMs reveals, in this setting, the presence of very fast (high frequency), non-physiological signals
- oversensing can be replicated by isometric movements of the arm ipsilateral to the can or by manipulation of the lead in the pocket