Ventricular undersensing

Tracing

N° 1

Manufacturer Boston Scientific Device PM

Patient

Graph and trace

Comments

This tracing illustrates a case of ventricular undersensing revealed by the presence of a RYTHMIQ switch
Ventricular undersensing is followed by backup pacing and switch to DDD mode
A good quality ventricular sensing, atrial sensing and atrial pacing is required for the RYTHMIQ algorithm to work properly
Recording an EGM in case of switch to DDD allows the diagnosis of even intermittent dysfunctions
Traditionally, unlike ICDs, pacemakers functioned with a fixed and stable sensitivity throughout the cardiac cycle
Modern pacemakers allow the programming of an ICD-like adaptive sensitivity (variable sensitivity levels according to the amplitude of the R wave or the sensed P wave with progressive increase in sensitivity during the cardiac cycle)
In Boston Scientific^TM pacemakers, the 2 options are available: fixed sensitivity or adaptive sensitivity (automatic gain control, AGC)
The type of sensing method used (AGC or Fixed) must be the same for both leads
Atrial and ventricular sensitivity values can be programmed independently
If sensing is programmed on AGC, the nominal sensitivity value is 0.6 mV for the ventricle and 0.25 mV for the atrium