Seventy-two year old man implanted for primary prevention with a single chamber ICD Marquis VR for ischemic cardiomyopathy and poor LVEF (<30%). The reason of the consultation was syncope.
This patient had episodes of VT bordering the inferior limit of the tachycardia zone. The onset of the tachycardia is not visualized, as it is slower than the heart rate detection criteria. Programming the appropriate VT zone is essential for the good function of the discriminators. The sudden onset is useful to distinguish a relatively slow VT from sinus tachycardia (where the onset is usually gradual). The sudden onset is never used for redetection. The sudden onset can be misleading in 2 situations : 1) in patients presenting VT during exercise (In this situation, the change in cycle duration between the sinus tachycardia and the VT can be minimal). 2) in patients like this one, when the VT cycle is relatively similar to the programmed inferior limit of the VT zone.
Tow detection zones are programmed. The detection enhancement algorithm functions only in the VT zone. The 3 criteria are programmed but the morphology is on « monitor ». In the absence of sudden onset, the VT detection is reported and the ICD interprets the rhythm as a SVT.
