undersensing
Failure of a pacemaker or ICD to detect intrinsic cardiac electrical activity when it should be sensed.
Full Definition
Undersensing occurs when a cardiac device fails to recognize intrinsic electrical signals that exceed the programmed sensitivity threshold, resulting in inappropriate pacing or therapy delivery. This malfunction can manifest as pacing spikes during intrinsic rhythms (competitive pacing) or failure to inhibit pacing when intrinsic activity is present. In ICDs, undersensing may prevent appropriate therapy delivery during life-threatening arrhythmias. Common causes include inadequate sensitivity settings, poor lead positioning, lead maturation, scar tissue formation, low-amplitude signals, or lead dysfunction. Diagnosis requires careful analysis of device electrograms and comparison with surface ECGs to identify missed intrinsic beats.
Usage
Usage note: Distinguish from oversensing; specify affected chamber and underlying cause when possible.
In Context
- "Undersensing of atrial activity resulted in inappropriate ventricular pacing during sinus rhythm." — Device malfunction report
- "Sensitivity adjustment from 2.0mV to 1.0mV resolved the undersensing problem." — Device reprogramming note