72-year-old man, recipient of an InSyncSentry CRT-D for ischemic cardiomyopathy, left ventricular ejection fraction of 20%, NYHA functional class III and left bundle branch block. Episodes of VT stored in the device memory were identified at a routine ambulatory visit.
Inappropriate therapy (e.g. shock therapy for AF or lead fracture) can be distinguished from unnecessary therapy (shock therapy for VT or VF that ends spontaneously). As illustrated by this episode, a considerable proportion of patients suffer multiple episodes of non-sustained VT that do not require therapy. An objective of device programming is to extend the detection to allow the spontaneous termination of tachycardias without compromising safety. In the VF zone a shock is not delivered until the number of intervals to detect has been reached and the capacitors have charged up. It would be appropriate, in this patient, to extend the detection interval in the VF zone to avoid the battery drain associated with repetitive charges of the capacitors. Programming a NID in the VF zone to 30/40 as a nominal value in primary prevention has been found to be safe in most patients.
The diagnosed episode of VF lasted 7 sec. The capacitor charged up, though shock therapy was aborted when the VT ended spontaneously. The TS event is in the VT zone. The events in the FVT via VF zone are labelled ‘TF*’ and these cycles are also counted as VF (NIDFVT = NIDVF). VF is diagnosed because 1 of the last 8 intervals is in the VF zone.
