Ventricular undersensing

ventricular undersensing

Patient

This 28-year-old woman received a Lumax 540 VR-T single chamber defibrillator after an episode of aborted sudden cardiac death. An event report (yellow color) was issued in the context of supraventricular tachycardia (SVT).

Main programmed settings

VF zone (270 ms) and VT1 zone (350 ms)
12/16 cycles in the VF zone and 26 cycles in the VT1 zone were needed for the diagnosis
Maximum sensitivity programmed at 0.5 mV
Effective discrimination in the VT1 zone
VF zone: 1 burst of ATP, followed by 8 shocks of maximum strength (40 J); VT1 zone: monitor zone without programmed therapy
Pacing mode: VVI at 30 bpm

Trace

Remote tracing

The 3 channels available are 1) the markers with the time intervals, 2) the shock channel (FF = far field) between the coil of the RV lead and the pulse generator, and 3) the right ventricular (RV) sensing channel.

fast, spontaneous rhythm with cycles classified in the VT1 zone;
ventricular extrasystole classified in the VF zone;
ventricular undersensing with following cycle classified VS;
ventricular extrasystole classified in the VF zone with compensatory pause and following cycle classified VS;
episode classified SVT when the VT1 counter is full; VS cycles decrease the counter by 1 and VF cycles increase the VT1 counter by 1. This episode was classified SVT because of its irregularity (99 ms) after the sudden onset criterion was fulfilled;
no delivery of therapy;
persistence of ventricular undersensing.

Programmer tracing (same episode)

The 3 channels are the same as for the remote tracing.

the undersensed cycles are low-amplitude signals occurring after a higher-amplitude ventricular event (probable extrasystole);
undersensing after a non-premature ventricular event.

Pacing & Defibrillation

ECG

Library

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