From Ask Dr Wiki
Causes
- Mechanically damaged lead
- Electrical far field atrial signals sensed from a dislodged lead
- Electrical far field atrial signals that are sensed during loss of AV synchrony
- high frequency, low amplitude signals that originate from chest cavity or abdominal muscles
- External electrical or RF sources
Incidence
- Main source of inappropriate shocks in selected groups of patients
- May occur in up to 14 % of patients
- More common in HOCM, dilated, Long and short QT, Brugada, Hyperkalemia and Sarcoid
- Incidence of T wave oversensing in Bipolar (17 %) versus Integrated bipolar (4.3 %)
Management
- Decreasing Ventricular sensitivity (0.3 mv to 0.6 mV to 1.2 mV). Retest DFTs
- Program longer postventricular sensing refractory period, because T wave oversensing will result in PVC response which will increase PVARP resulting in functional P wave undersensing
- Post ventricular refractory after a sensed event is not programmable in Medtronic or Boston Scientific devices. St. Jude is programmable to 125 or 157 msec.
- Post ventricular refractory after paced events is programmable with St. Jude, Medtronic and BS
- Increasing the detection interval count
- Program the tachycardia detection rate twice the expected sinus rate
- Use of Beta blockers to decrease the sinus rate range
- Repositioning of the RV lead to obtain high RV sensing amplitude
- Implantation of endocardial pace/sense lead to an area with higher RV sensing amplitude
- Implantation of epicardial lead for pace/sense
- Test for oversensing
- CXR
- Pocket manipulation
- Isometric Resistance exercises
- Valsalva
- Forced Cough
- Perform all tests in the supine, sitting, and erect position
