76-year-old man implanted with a Lumax 540 VR-T single-chamber ICD for dilated cardiomyopathy with ejection fraction of 25%; event report (yellow color) in the setting of a classified VT1; programming of a VT1 zone (350-290 ms) with effective discrimination (onset 20%, stability 24 ms).
3 channels are available: the markers with the time intervals, the shock channel (FF: far field) between the ventricular lead coil and the pulse generator, the right ventricular sensing channel (RV).
This tracing illustrates the challenges in the discrimination of an atrial tachycardia or flutter with a single-chamber ICD. Typically, during an atrial tachycardia or a flutter, as in the case of a VT, there is a sudden onset and a stable rhythm. In this patient, the morphology of the signal (not integrated in the discrimination algorithm for this platform) is clearly suggestive of a supraventricular origin (identical morphology). The antitachycardia pacing sequence may therefore be considered inappropriate. It nevertheless allowed terminating the arrhythmia. The termination of an atrial tachycardia stemming from a ventricular antitachycardia pacing is relatively common; the termination of the tachycardia by ATP cannot therefore be considered as an element suggestive of a ventricular origin of the tachycardia. It was therefore chosen for this patient not to modify the programming (no possibility in terms of discrimination but possibility of reducing the intervention zones) despite the inappropriate nature of the therapies.
