An inappropriate defibrillator shock during ventricular tachycardia

Area of Science:

• Cardiology
• Electrophysiology
• Medical Device Technology

Background:

• Ventricular oversensing is a rare but serious complication in patients with implantable defibrillators.
• It can lead to inappropriate and potentially harmful therapies.
• Cardiac resynchronization-defibrillation (CRD) devices are used for heart failure and arrhythmia management.

Purpose of the Study:

• To report a case of ventricular oversensing due to double-counting in a patient with a CRD device.
• To illustrate how this oversensing led to inappropriate shock delivery.
• To emphasize the importance of device interrogation for accurate diagnosis and therapy.

Main Methods:

• Case report of a patient presenting with syncope and hyperkalemia.
• Device interrogation of a cardiac resynchronization-defibrillation system.
• Analysis of electrogram data to identify the cause of oversensing and inappropriate therapy.

Main Results:

• The patient experienced syncope attributed to hyperkalemia.
• Device interrogation revealed ventricular oversensing due to double-counting of the QRS complex during slow ventricular tachycardia.
• This led to the device misclassifying the rhythm as ventricular fibrillation and delivering an inappropriate therapy.

Conclusions:

• Ventricular oversensing, even with advanced CRD devices, remains a clinical challenge.
• Double-counting within the QRS complex is a potential mechanism for inappropriate detection.
• Thorough electrogram interrogation is crucial for diagnosing oversensing and preventing unnecessary defibrillator therapies.