Far-field atrial sensing by the left ventricular channel of a biventricular device

The left ventricular (LV) channel of Biotronik biventricular devices used for cardiac resynchronization therapy (CRT) is designed with the capability of sensing via the LV lead. Therefore a displaced LV lead in a coronary vein could sense far-field atrial signals and interfere with CRT.

The Biotronik troubleshooting archives containing data of approximately 700 transvenous CRT-D cases (D = defibrillator) were examined for atrial far-field sensing by the LV channel. We selected three cases from the archives to demonstrate the typical features of LV sensing of far-field atrial activity.

We found 3 typical cases of far-field atrial sensing by the LV channel. The LV lead was displaced in 2 cases and possibly in the third patient. Two cases exhibited short intervals between LV sensed events (LVs-LVs = 207-218 ms), a finding typical of this form of far-field atrial sensing by an LV lead. In the third case, short LVs-LVs intervals were not observed because spontaneous LV activation failed to generate an LVs marker (corresponding with the terminal LVs marker in a short LVs-LVs interval). LV activity was unsensed during the blanking period of the LV upper rate interval initiated by the first LVs that actually generated by far-field oversensing. This response was also observed intermittently in a patient who presented with short LVs-LVs intervals.

Far-field atrial oversensing by the LV channel of a CRT-D device occurs mostly with LV lead displacement. The diagnosis is important because it interferes with the delivery of therapeutic CRT but it is not life-threatening. Oversensing can be easily corrected by simple reprogramming of the device or LV lead repositioning if there is high LV pacing threshold.