A case of wearable defibrillator failure: How one lifesaving therapy delays another.

Use of a wearable cardiac defibrillator (WCD) is indicated for primary prevention of sudden cardiac death for patients ineligible for implantable cardioverter-defibrillators. While published reports of WCD rhythm detection algorithm demonstrate effective detection of ventricular tachycardia and ventricular fibrillation (VF), clinical studies show some patients wearing the WCD are not successfully resuscitated. We present a case of a patient who did not receive an appropriate shock while wearing a WCD despite the device's initial detection of VF. We hypothesize that the onset of bystander cardiopulmonary resuscitation was responsible for hindering the detection algorithm, ultimately canceling the appropriate rescue shock. <Learning objective: The purpose of this case is to draw attention to the possibility that a wearable cardiac defibrillator may not deliver life-saving shock therapy due to initiation of bystander cardiopulmonary resuscitation (CPR). During the detection window, it is possible for bystander CPR to create significant noise on the detection channels. This noise may cause the defibrillator to mis-interpret the arrhythmia as artifact and in turn inhibit life-saving therapy.>.