Abstract 235: Post-shock Asystole And Inappropriate Shocks In Patients Dying Out-of-hospital While Wearing A Defibrillator

Abstract

Background: The LifeVest wearable defibrillator (LWD) is prescribed for patients who are at risk for sudden cardiac death. However, it does not provide backup pacing for post-shock asystole (PS-A) or post-shock bradyarrhythmia (PS-B;<50 bpm). We sought to determine if this limitation may have impacted outcomes in patients treated with the LWD who died out-of-hospital (OOH). Also, we assessed the incidence and clinical consequences of inappropriate shocks (IAS) in these patients. Methods: The U.S. Food and Drug Administration's Manufacturers and User Facility Device Experience (MAUDE) database was queried for the manufacturer's descriptions of events and stored ECG findings of patients who died OOH while wearing the LifeVest. Excluded were LWD patients who did not receive a LWD shock during the terminal event. Results: From January 2017-March 2022, 543 patients died OOH and received at least one LWD shock (avg 3.9±4.5SD; range 1-34). Of these, 120 (22.1%) had PS-A alone, 26 (4.8%) had PS-B alone, and 85 (15.5%) had both PS-A and PS-B. PS-A first occurred after shock #1 (n=127; 62.0%); shock #2 (n=29; 14.1%); shock #3 (n=18; 8.8%), and shocks #4 to #18 (n=31;15.1%). For the 205 (37.8%) patients who had PS-A with or without PS-B, the rhythms appropriately shocked were ventricular fibrillation (VF; n=121; 59.0%) and ventricular tachycardia (VT; n=63; 30.7%). Of the 184 patients whose initial rhythm was VF/VT, 118 (64.1%) died in asystole after the first and only shock, 40 (21.7%) died in asystole after the second (n=23) or third shock (n=17), and 26 (14.1%) died in asystole after the fourth to eighteenth shock. Twenty-one patients died when asystole occurred after they received IAS for atrial fibrillation (n= 3), supraventricular tachycardia (n= 4), and sinus (n=4) or idioventricular rhythm (n=10). Overall, 70.3% (382/543) of patients received one or more IAS (avg 2.7±2.8SD; range 1-26). Conclusion: Post-shock asystole and post-shock bradycardia are common in patients who die after receiving appropriate LWD shocks. Most patients received one or more IAS, and some were lethal. Whether back-up pacing and better rhythm and noise discrimination could improve outcomes warrants investigation.