Novel Automatic Shocking-Vector Adjustment Algorithm: A Life Saving
Feature of a Modern Defibrillator.
Abstract
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.