PMK troubleshooting Flashcards
What is pectoral myopotential noise?
Pectoral myopotetial signal are high-rate signal oversensed in unipolar lead configuration. In a pacing dependent patient pacing inhibition due to pectoral myopotentials may be potentially lethal as it may lead to asystole. Prayer manoeuvre, pressing both hand against each other can illicit this noise.
What is paradoxical atrial undersensing of AF?
Atrial sensitivity level that is too high can lead to atrial oversensing, noise reversion, and absence of mode switch, with tracking of atrial events that fall outside of the noise reversion window. Can occur due to noise reversion or “ringing”. Ringing corresponds to the saturation of the sense amplifier (usually due to atrial arrhythmias with high-amplitude signals) and can be distinguished from noise reversion by the absence of sense markers.
How to rule out electromagnetic interference from other types of noise?
EMI would be present on all EGMs, far-field and near-field.
Usually repetitive and high rate (e.g 50 Hz)
Artefacts visible simultaneously on all channels
Amplitude on far-field > near-field EGM
How are diaphragmatic myopotential characterized?
Low-amplitude, high frequency artefact. Reproducible during Valsalva manoeuvre.
Only visible on ventricular lead
How to distinguish myopotential artefacts?
Usually of high rate, with sometimes crescendo-decrescendo amplitude
Diaphragmatic myopotentials only observed on the ventricular channel, with amplitude near-field > far-field EGM
Pectoral myopontentials may be observed in any lead programmed to unipolar sensing
May be reproduced by provocative manoeuvres (Valsalva manoeuvre, cough, prayer manoeuvre).
What characterizes lead fracture artefacts?
Usually of erratic morphology and high amplitude (channel saturation)
Only observed on a single EGM channel (or on the channels of all fractured leads, but usually not perfectly simultaneously)
May be associated with elevated lead impedance or abnormal threshold (but electrical parameters may be normal)
May sometimes be provoked by manipulation of the pocket (if the fracture is in the extrathoracic portion of the lead)
What is negative AV hysteresis?
This device feature is designed to respond to events with intrinsic AV conduction to maximize ventricular pacing. As AV conduction may be different during 24 hr, loss of CRT may be avoided in situations where AV conduction is facilitated (e.g during exercise). However with VPB this feature may lead to reduced ventricular filling (due to A-wave truncation) and unfavorable hemodynamic consequences.
What may cause ventricular failure to output and what differential diagnosis should be considered?
The two most common causes of failure to output are lead fracture or pin not fully inserted into the header. another possible explanation could be inhibition to output due to some other cardiac or external activity being sensed consistently.
Name potential explanations for paced rates below the programmed lower rate limit.
- Device malfunction due to oversensing by the ventricular lead (due to extracardiac interference or innapropriate sensing of other cardiac events, eg. T wave oversensing)
- Open circuit ?
- Battery depletion
- Automated capture algorithms
- PVARP extension algorithms after frequents PVCs
- Rest or sleep mode
- Heart rate hysteresis
What is search positive AV interval hysteresis?
Specific type of hysteresis in which there is periodic prolongation of the PR interval after a ventricular paced event.
What is an open circuit and what are possible causes for its occurrence?
Open electrical circuit is a condition which prevents the pacemaker output from reaching the heart. It can occur when there is a fracture of the conductor coil, or the connector pin is not being secured adequately in the header of the pulse generator.
