83-year-old man implanted with a Lumax 540 HF-T triple-chamber ICD for heart failure with left bundle branch block; remote monitoring alert for several episodes of VF without delivery of therapy.
Telemedicine tracing: 4 channels are available; the markers with the time intervals, the atrial channel (A), the right ventricular sensing channel (RV) and the left ventricular channel (LV).
Programmer tracing (identical episode): the 4 channels are the same as for the telecardiology tracing.
This tracing shows a characteristic pattern of lead dysfunction associated with the occurrence of multiple episodes of charging of the capacitors. The oversensing could be reproduced by thwarted maneuvers favoring the oversensing of pectoral myopotentials which could already be evoked on the tracing given the high frequency of sensed signals. The preponderance of short intervals versus long intervals explains that the 75% ratio required to fill the initial counter is met (18/24). Most commonly, lead dysfunction is initially revealed by short episodes diagnosed as non-sustained VT (a few intervals). The duration of the oversensing episodes generally increases progressively in parallel with the wear of the lead. In order to avoid the occurrence of inappropriate therapies, it is clear that in addition to a rapid diagnosis supported by a remote follow-up, one solution is to extend the number of intervals required for the initial diagnosis of VF. Nowadays, the new guidelines favor the first-line programming of initial counters at 30/40 even without signs of lead dysfunction. Results obtained on large-scale samples showed that this programming significantly reduced the number of inappropriate therapies but also the number of appropriate but avoidable therapies, with the arrhythmia terminating spontaneously without significantly increasing the risk of syncope.
