SecureSense™ algorithm and use of the electric scalpel
This 65-year-old man was implanted with a Abbott Ellipse™ DR defibrillator. He received an electric shock during a surgical procedure.
- oversensing is visible on the atrial, ventricular and discrimination channels; the VF counter is filled; the noise counter has often been reset to 0 after the occurrence of short cycles on the discrimination channel; the capacitors begin to charge;
- return to sinus rhythm diagnosed after 3 VS-classified cycles;
- oversensing of large, fast and disorganized signals on both ventricular channels;
- further oversensing;
- the VF counter is filled (12); the noise counter is incessantly reset to 0; the therapies are not inhibited; the capacitors are charging;
- short charge since the capacitors were already partially charged; at the end of the charge, new verification of the noise counter, which is <10; a 30-J shock is delivered;
- interruption of oversensing and return to sinus rhythm diagnosed after 3 consecutive VS cycles.
When a ICD recipient undergoes a surgical procedure, the surgeon must be advised to use the electric scalpel in the bipolar mode for brief periods, and to place the plate electrodes away from the pulse generator to keep the defibrillation system outside of the field created by the electric scalpel. The ICD must be temporarily deactivated to eliminate the risk of interference, and the patient must be monitored, with an external defibrillator available, if necessary. The device can be deactivated by applying a magnet over the can, or by deprogramming the device. The application of a magnet is usually preferred since, should a life-threatening arrhythmia develop, the ICD can be immediately reactivated by removing the magnet, which allows the immediate resumption of the detection of ventricular tachyarrhythmias. The absence or delay in the reactivation of therapies is not rare if the ICD was deprogrammed.
The aspect of the intracardiac EGM detected by the device is characteristic if its detection has not been deactivated, with presence of large, disorganized, and fast signals observed on the atrial, the bipolar and the discrimination channels. The coincidence with the surgical intervention confirms the diagnosis in most cases. The basic function of the SecureSense™ algorithm is the reason why the therapies are not inhibited for this type of oversensing, as the presence of short cycles on the discrimination channel reset the noise counter incessantly.