An intuitive method to reduce the defibrillation threshold: a case report

Defibrillation threshold (DFT) testing is done to assess whether proper sensing of ventricular fibrillation and adequate safety margin for defibrillation are present in an implantable cardioverter defibrillator (ICD). This case report presents an intuitive method for lowering the DFT. It may be used on a larger scale in other patients with high DFTs when other methods for lowering the DFT (changing medications, adjusting the device, and adding coils) are not feasible or preferable to use.

A 64-year-old male presented to the emergency room with failed appropriate shocks from his ICD. Device interrogation revealed that he failed his first maximum output shock before subsequent shock at the same polarity and output succeeded, suggesting a high DFT. Therefore, the DFT needs to be lowered in our patient. After considering the potential efficacy and risk of a number of traditional options, we used an intuitive method whereby the right ventricular (RV) coils of two separate leads were combined via a y-adapter. This method successfully lowered the patient's DFT, and he received successful shocks from his ICD over the next 9 months before reaching end-stage heart failure. He received a transplant, and the device and transvenous leads, except for the superior vena cava coil, were successfully removed.

Combining two RV coils from different locations may lower the DFT. This method may be considered in the larger population in cases where using traditional methods are not safe or possible for certain patients. This method may work by lowering shock impedance and increasing the shock tissue surface area.