Prolongation of the initial VF counter

N° 5
Manufacturer Medtronic Device ICD Field Counter

Patient implanted with a single-chamber ICD (Visia AF XT VR) for ischemic cardiomyopathy; multiple episodes of NSVT stored in the device memory; an episode with electrical shock; this tracing suggests the advantage of programming the initial counter at 30/40 in order to reduce the occurrence of appropriate but avoidable therapies.

Graph and trace

The graph shows a tachycardia detected in the VF zone; in spite of a relatively high number of intervals detected in the VF zone, the VF counter is not filled; spontaneous termination of the episode.

  1. the EGM shows a wide QRS tachycardia (far-field channel) with intervals primarily detected in the VF zone; in spite of 26 intervals classified as FS, the VF counter is not filled (programmed at 30/40);
  2. spontaneous termination of the episode.

This patient presented multiple episodes of non-sustained ventricular tachycardia stored in the memory of the device and defined by the occurrence of at least 5 consecutive intervals in one of the detection zones without any of the initial counters being filled (VT or VF). For a same patient, the greater the number of required intervals (30/40 versus 9/12), the higher the probability of recording an episode of non-sustained ventricular tachycardia. The programming of this parameter is crucial for the quality of life of the patient but also for his or her prognosis. Indeed, programming 30/40 beats for initial detection not only reduces the number of inappropriate therapies due to lead dysfunction or due to an episode of supraventricular tachycardia, but also reduces the number of appropriate but avoidable therapies. When associated with the programming of relatively high detection zones, this translates into a significant reduction in mortality in primary prevention. Treating an episode of malignant ventricular arrhythmia with electrical shock is the only option for achieving viable hemodynamics. On the other hand, the latest recommendations, based on the most recent studies, suggest the need to avoid treating slower and organized ventricular arrhythmias too prematurely or too aggressively. An electrical shock can save a life but is associated with a deleterious effect on its own and should therefore be avoided whenever possible when spontaneous termination is possible or a less aggressive therapy can be effective. It is therefore advisable 1) not to systematically program treatment zones that are too low for primary prevention; 2) to prolong the initial detection counters in the VT zone but also in the VF area in order to avoid treating spontaneously-terminating arrhythmia episodes (appropriate but avoidable therapies); 3) to promote a first-line treatment with anti-tachycardia pacing even for very fast tachycardias (limit: 230-250 beats/minute).

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