Abstract 1771: Analysis of Sudden Cardiac Arrests During Wearable Defibrillator Use
Background: Wearable cardioverter-defibrillators (WCD) are a possible solution to many transitory sudden death risk situations when implantable defibrillators or hospitalization is impractical or unwarranted. However, published data on efficacy and use is limited. We analyzed 45 sudden cardiac arrests (SCA) that occurred between January 2005 and April 2006.
Methods: The WCD (LifeVest 3000, ZOLL-LIFECOR, Pittsburgh, PA) automatically records and treats ventricular arrhythmias (VT/VF) without the need for a bystander. The entire arrhythmia, treatment, 15 seconds following termination and 30 seconds prior to the determination of VT/VF are stored. Asystole (rate < 3 beats per minute or QRS complex less than 100 mcv) is not treated but is recorded including 5 minutes prior to the determination. ECG recordings and customer call reports were reviewed for death while wearing WCD. Medical orders were reviewed for determining WCD indication. SCA events were defined as all potentially life-threatening arrhythmias occurring within a single 24-hour period.
Results: There were 47 SCA events identified in 33 patients: 38 VT, 2 VF, 7 asystole and 1 electromechanical dissociation (EMD). VT/VF recurred within 24 hours in 3 events. All events were detected and recorded by the WCD with the exception of EMD reported to have occurred on a telemetered patient. All VT/VF events were treated successfully (converted out of VT/VF and either conscious ER arrival or no need for additional care). Two patients were shocked for sustained VT while conscious. Most (84%) were treated within 60 seconds (VT programming and response button use were most frequent cause of shock delay). Median time to shock from arrhythmia onset was 44 seconds (range: 29 to 3600 seconds). 4 of 7 asystole events survived. Patients consisted of ICD explants or surgical delays (76%), prior VT/VF (15%), post-MI/CABG with low EF (15%), genetic SCA risk (9%), non-ischemic cardiomyopathy (3%) or unknown (3%).
Conclusions: The majority of SCA in this population was due to VT/VF (84%). When in use WCD successfully treated 100% of VT/VF. Overall SCA (unshockable rhythms included) survival was 87%.