Background: Failed delivery of appropriate shocks against fatal arrhythmias can be the result of low impedance on high-voltage leads. This malfunction might be missed on routine interrogation. We describe a case of 66 year-old male with a high-voltage lead short circuit who was successfully rescued with the use of an overcurrent detection and automatic shocking vector adjustment algorithm. Case Report: A 66-year-old male with severe nonischemic cardiomyopathy was admitted after receiving two shocks from his cardiac resynchronization therapy cardioverter-defibrillator (CRT-D). Interrogation confirmed two 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/can. 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 CRT-D can (Figure 1B). This successfully terminated the ventricular fibrillation. All other lead measurements were normal. Conclusions: High voltage lead malfunctions can lead to failed therapy of life threatening arrhythmias. Malfunctions such as 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 arrhythmias. With these algorithms - overcurrent detection and automatic shocking vector adjustment, this patient was successfully rescued. We recommend this feature be included in all modern defibrillators.