Case Report of Novel, Automatic Shocking Vector Adjustment Algorithm: A Life-Saving Feature of a Modern Defibrillator

Failed delivery of appropriate shocks against fatal dysrhythmias can be the result of low impedance on high-voltage leads. This malfunction might be missed on routine interrogation. We describe the case of a 66-year-old man with a high-voltage lead short circuit who was successfully rescued with the use of an overcurrent detection and automatic shocking vector adjustment algorithm.

A 66-year-old man with severe nonischemic cardiomyopathy was admitted after receiving 2 shocks from his cardiac resynchronization therapy cardioverter-defibrillator. Interrogation of his defibrillator confirmed 2 consecutive episodes of ventricular fibrillation. For each episode, the initial shock therapy was aborted due to low impedance (<10 ohms) detected on the default shocking configuration: right ventricle to superior vena cava/implantable cardioverter generator. As a result, the device algorithm excluded the superior vena cava coil and immediately delivered a shock of 40 joules between the right ventricular coil and the cardiac resynchronization therapy cardioverter-defibrillator implantable cardioverter generator. This successfully terminated the ventricular fibrillation. All other lead measurements were normal.

High-voltage lead malfunctions can lead to failed therapy of life-threatening dysrhythmias. Malfunctions like a low impedance of high-voltage leads may not be detected on routine interrogation. Fortunately, the overcurrent detection algorithm recognized the low impedance, and another shocking configuration was selected and successfully terminated the ventricular dysrhythmias. With these algorithms, overcurrent detection and automatic shocking vector adjustment, this patient was rescued. We suggest this feature be considered in all modern defibrillators.