Abstract Body (Do not enter title and authors here): Background: The wearable cardioverter defibrillator (WCD) can prevent sudden
cardiac death (SCD). It also provides continuous monitoring for detection of
significant cardiac arrhythmias.

Hypothesis: Detection of ventricular and atrial arrhythmia by the WCD can significantly impact clinical decisions and outcomes.

Aims: Report occurrence of ventricular tachycardia/fibrillation (VT/VF) and atrial fibrillation/flutter (AF/AFL) detected by the WCD and clinical consequence of these diagnoses.

Methods: Retrospective analysis of patients prescribed the ASSURE WCD at the Cleveland Clinic. Clinical data were collected via medical chart review. Rhythm classification, of all device-detected and patient-initiated episodes displayed with 4 independent ECG channels, was manually adjudicated by a Board-Certified Electrophysiologist.

Results: Fifty-five patients were fitted with the WCD between January 2023 and April 2024. Overall median daily use was 22 hr/day (IQR 13-24) and median duration of use was 43 days (IQR 8-79). Mean age 60.1 ± 17.6 years; 49% females; 40% ischemic cardiomyopathy; 44% nonischemic cardiomyopathy; 16% other etiology; mean Ejection Fraction (EF) 31.5 ± 6.9% pre-WCD and 38.6 ± 9.3% post-WCD.
Arrhythmia occurrence in this cohort is shown in Figure 1. Four patients (7%) had sustained VT/VF detected by the WCD, consequently all received a secondary prevention ICD. Notably, 2 patients were asymptomatic and only aware because of the device alerting of an imminent shock. Both patients showed significant recovery of EF >35% during the WCD wear period, and had sustained VT/VF not been detected by the WCD, neither would have met indication for a prophylactic ICD. Additionally, 6 patients (11%) had AF/AFL recorded by the WCD. In 3 patients AF/AFL manifested in a paroxysmal pattern and the diagnosis was new. All were at high risk for stroke with median CHADS-VaSC=4 (IQR 4-6).

Discussion: In addition to its primary utility for preventing SCD, the WCD can detect occult yet clinically significant arrhythmia. Detection of sustained ventricular arrhythmia in asymptomatic at-risk patients resulted in secondary prevention of SCD. Documentation of AF/AFL in high-risk patients could similarly lead to impactful risk reduction.