Inappropriate Defibrillator Shock Due to Oversensing. What to Do?

In spite of advanced designs of implantable cardioverter defibrillators (ICD) lead fracture remains the most frequent complications. ICD interrogation is mandatory for the diagnosis of all type of lead failures.

We report the case of an 18 years old boy, diagnosed with Jarvell and Lange Nielsen syndrome since he was 2 years. He received first Nadolol then he got ICD and a prophylactic left sympathectomy after he had a cardiac arrest. One year later, the ICD started delivering shocks, appropriate at first then inappropriate due to oversensing.

Long QT syndrome is a rare congenital disorder characterized by repetitive episode of syncope and cardiac arrest due to polymorphic ventricular tachycardia. The treatment is mostly pharmaceutical with B-blockers. The indication for an ICD is in class I for patients who survived cardiac arrest, and for patients who experience recurrent syncopal events under B-blockers. On the other hand, in case of contraindicated or not tolerated medical therapy, ICD is recommended as a class IIa, according the ESC guidelines of 2022.

An ICD must be interrogated frequently and have its measurements reviewed in order to detect lead dysfunction. The detection of high impedance suggests conductor fracture along with inappropriate defibrillator shocks delivered by the ICD.

Oversensing with normal pacing impedance is the initial electrical abnormality with either conductor fracture.(4)

The fractured lead will either be left inside the patient or removed, depending on specific factors related to the patient and the ICD. (5)