This 58-year-old man received a Lumax 540 HF-T triple chamber defibrillator, implanted for a primary prevention indication in the context of ischemic cardiomyopathy with a 30% left ventricular ejection fraction, left bundle branch block and sinus node dysfunction; event report issued (yellow color) in the context of multiples episodes of VT and one episode of VF.
Main programmed settings
- VF zone (280 ms limit), VT2 zone (400 ms limit) and VT1 zone (460 ms limit)
- 12/16 cycles in the VF zone, 16 cycles in the VT2 zone and 26 cycles in the VT1 zone were needed for the diagnosis
- Maximum sensitivity programmed at 0.8 mV
- VF zone: delivery of a single burst of ATP one shot, followed by 8 shocks of maximum strength (40 J); VT2 zone: 3 bursts, followed by 3 ramps, followed by 1 shock at 16 J, followed by 7 shocks of maximum strength; VT1 zone: 3 bursts, followed by 3 ramps; no shock programmed
- Effective discrimination in both VT zones
- Pacing mode: DDDR at 60 bpm with biventricular stimulation
Remote report
Multiples episodes classified in VT2 zone with 1 to 2 ATP delivered over approximately 6 months. One episode was classified in the VF zone with a cancelled shock.
Remote tracing 1 (no 35)
The 4 channels available are: 1) the markers with the time intervals, 2) the atrial (A) channel, 3) the right ventricular (RV) sensing channel and 4) the left ventricular (LV) channel.
On the summary table, the type of episode (VT2) corresponds to the first classification; the VT2 reclassification indicates that, after the first therapy (burst), the reclassifying VT2 counter was filled, prompting the delivery of a second therapy.
- atrial paced rhythm (sensor-driven rate) and biventricular stimulation. The “PermDDDR” labeling at the onset of the tracing indicates that the defibrillator operated in the permanently programmed (DDDR) pacing mode;
- late VES of LV origin, as the LV falls before VS, after atrial pacing; the VES, on the right hand side, falls in the post atrial pacing safety window. The device paced during the safety window, explaining the 2 closely spaced lines on the RV markers (sensing followed by pacing); a pacing artifact is visible at the level of the ventricular EGM (inside the extrasystole);
- sudden onset of tachycardia detected in the VT2 zone; atrioventricular dissociation with a very slow atrial rate, in this patient presenting with known sinus node dysfunction. The atrial cycle is classified “Ars” as it fell in the post ventricular atrial refractory period (PVARP). It is noteworthy that the defibrillator treated it as a succession of VES, causing the systematic lengthening of the PVARP, which, starting with the Lumax 740 model, is nominally programmed at 225 ms with a 150-ms extension after a VES;
- classification of a VT2 episode after 16 cycles in the VT2 zone without interposed cycle classified VT1 or VS. The device diagnosed VT because the ventricular rate was faster than the atrial rate (RR<PP);
- two sequences of ATP were needed to terminate the arrhythmia. The end of the second sequence of ATP is visible, consisting of a burst of RV pacing. Triple chamber devices allow the programming of RV, LV or biventricular bursts;
- termination of the arrhythmia;
- end of the episode after 12 consecutive paced ventricular cycles (≥12 out of 16 slow cycles);
Remote tracing 2 (no 24)
- episode of VT identical to the previous;
- the end of the sequence of ATP is visible;
Remote tracing 3 (no 20)
- spontaneously terminated, nonsustained VT;
- new salvo of 10 complexes of nonsustained VT;
- longer salvo classified as VT2 when the counter is full; burst of ATP and termination; it is noteworthy that the VT is consistently the same, with identical RV and LV morphologies of all episodes;
Remote tracing 4 (no 38)
- episode classified VF;
- an extremely rapid signal is intermittently detected on the atrial, RV and LV channels (As, Ars, Vs VT1, VF markers);
- episode classified VF; if one counts from this classification backward, 12 of the 16 previous cycles are classified VF, which corresponds precisely to the VF zone counter;
- start of the charge of the defibrillator’s capacitors;
- when the EGM return, the ultra rapid signal is only visible on the atrial channel, with intermittent oversensing; the noise on the RV channel has disappeared, explaining why the device considered that the episode had ended.
It is important, first of all, to confirm the accuracy of the diagnosis made by the device. In this case, it reported multiple episodes of actual VT and one erroneous diagnosis of VF due to oversensing of a 50 Hz signal. This patient was recalled for search and rapid identification of the source of the noisy signal (a defective household appliance), which eliminated all recurrences of inappropriate therapies.
This example brings up several important points: 1) this patient developed multiple episodes of VT of variable duration, sometimes ending spontaneously. In such cases the number of cycles needed for the diagnosis can be increased in order to facilitate a possible spontaneous termination, and to prevent ATP, which may not be inappropriate, though is sometimes unnecessary. 2) This completely asymptomatic patient presented with multiple episodes of VT, successfully treated by a sequence of ATP, which improved his quality of life preventing a succession of electrical shocks. 3) The programming of two zones of tachycardia allows the different treatment of two tachycardias with different rates. In the VT1 zone, which corresponds to tachycardias with rates below 170 bpm, it is customary to program different sequences of ATP (one series of 3 to 5 bursts of pacing at a fixed rate, followed by a series of 3 to 5 ramps of more aggressive bursts, with a programmable decrement of the pacing interval from one cycle to the next, before programming the delivery of a series of electrical shocks). For tachycardias detected between 190 bpm and the VF zone, it may be helpful to program a VT2 zone including fewer sequences of ATP in order to avoid an immediate treatment by shock, while not excessively delaying the delivery of shocks for these rapid tachyarrhythmias, which can compromise the patient’s hemodynamic status if ATP is unsuccessful.
