Atrial undersensing and decrease in the percentage of BiV stimulation

Tracing
N° 9
Manufacturer Biotronik Device CRT Field Standard parameters
Patient

This 71-year-old man received a Biotronik Lumax 540 HF-T triple chamber defibrillator in the context of ischemic cardiomyopathy with left bundle branch block. He was followed by remote monitoring and a periodic EGM was transmitted.

Graph and trace
  1. atrial sensing and BiV stimulation.
  2. absence of atrial sensing and sensing of spontaneous ventricular event (left bundle branch block with RV followed by LV sensing).
  3. atrial sensing and BiV stimulation.
  4. recurrent atrial undersensing and sensing of a spontaneous ventricular event.
Comments

This tracing shows a transitory decrease in the percentage of BiV stimulation due to atrial undersensing, revealed by the transmission of a periodic EGM without alert. As the percentage of BiV stimulation does not decrease below the threshold, a specific alert is not emitted. The tracing is not consistent with the sensing of a PVC, which must, by definition, be premature, unlike in this case. It might, on the other hand, be a ventricular escape in the context of sinus node dysfunction. This patient’s sinus node function was normal and atrial sensing in an average range, with a 0.6-mV P wave amplitude, characteristics consistent with atrial undersensing, which was corrected by reprogramming of the atrial sensitivity.