Patient - EN
Patient, recipient of a Abbott Current DR ICD was hospitalized for palpitations and an ICD shock.
Graph and trace
Main programmed parameters
- SVT discrimination timeout programmed ON (2 minutes)
Tracing
- diagnosis of SVT with a 1/1 atrio-ventricular conduction; the morphology of the 8 analyzed complexes is in favor of SVT (100%);
- new diagnosis of SVT every 6 beats;
- 2 minutes after the diagnosis of SVT (SVT discrimination timeout programmed ON at 2 minutes), delivery of a first burst;
- second burst;
- onset of charge of the capacitors;
- delivery of the 20 Joules shock;
- 5: slowing of the ventricular rate and diagnosis of return to sinus rhythm.
Take home message
Episode initially diagnosed as SVT in the V=A arm. The discriminators were discordant, as morphology indicated SVT while onset indicated VT. Hence, SVT was diagnosed and no therapy was initially delivered (all parameters required for VT). Then VT diagnosed (SVT timeout) despite the persistence of one discriminator in favor of SVT. 2 ATP and 1 shock are then delivered.
NID old - EN
1173
The device can be programmed for a maximal duration of arrhythmia, at the end of which therapy is delivered even if the tachycardia has been classified as SVT; this eliminates the risk of an untreated VT that has not been properly diagnosed by the device, at the risk of delivering inappropriate therapy for an episode of SVT that was accurately diagnosed as in this patient. This represents a "safety", which increases the sensitivity of the discrimination algorithm, at the cost of some specificity. The programming of this kind of parameter is an expression of limited trust in the ability of the device to discriminate flawlessly the tachyarrhythmias.
It is our practice to usually deactivate these clocks, in order to avoid inappropriate therapies delivered for episodes of accurately detected, sustained SVT.