Thirty-four year old man implanted with a single chamber ICD Protecta XT VR for Brugada syndrome and familial history of SCD. Routine follow-up.
This episode presents some typical characteristics of T-wave oversensing : it occurs during exercise, low R wave amplitude with a higher T-wave amplitude. T- and R-wave are alternatively detected by the ICD. Usually, these intervals would lead to the delivery of a shock.
In the present case, prolonging the R-wave refractory period to cover the sensed T-wave is not an option because it would reduce dramatically the range of detected rates. Adapting the ventricular sensibility is also not an appropriate option as the R-wave amplitude is already very low (reducing the ICD sensibility in this context might lead to a dangerous undersensing of a real episode of VF).
The T-wave oversensing algorithm is based on the analysis of the T-wave amplitude, frequency and RT pattern. It allows recognizing T-wave oversensing without compromising the R-wave detection or prolonging the R-wave refractory period. It works for both the initial detection and the redetection of the tachycardia. It is nominally programmed “ON”.
The detected tachycardia is fast (207 BPM) but no therapy is delivered because this episode was recognized by the ICD as an episode of T-wave oversensing.
