An Alarming Change: What Caused an Instance of Inappropriate Detection in a Wearable Cardioverter-defibrillator?

We describe the case of a patient who received cardiac resynchronization pacemaker therapy (CRT-P) incorporating bridge protection via a wearable cardioverter-defibrillator (WCD) while awaiting final evaluation for permanent placement of an implantable CRT device with defibrillation capabilities. In an attempt to mitigate symptoms of heart failure, reprogramming of the CRT-P with a V–V offset caused an unusual interaction and alarm from the WCD. This case highlights a unique interaction not previously reported and is clinically relevant to patients awaiting final evaluation for implantable defibrillator system placement.