High incidence of inappropriate alarms due to artifact sensing and misclassification of episodes in patients with wearable cardioverter-defibrillators
Authors: Lacour P L , Dang P D , Parwani A , Baehr F , Schoeppenthau D , Dagres N , Boldt L H , Hindricks G , Blaschke F 
Published: May 2024

Background

The wearable cardioverter-defibrillator (WCD) has become a useful tool used for temporary protection from sudden cardiac death. However, since the WCD uses surface electrodes to detect arrhythmias, it is prone to inappropriate detection. Although shock conversion rates for the WCD are high for detected events, its efficacy in clinical practice tends to be degraded by patient noncompliance. Reasons include wear discomfort and frequent false alarms, that may interrupt sleep and generate anxiety. Data on the incidence of false alarms emitted by the WCD and their predictors are rare.

Purpose

The aim of our study was to assess both artifact and misclassification burden and wear compliance in patients with a WCD.

Methods and Results

We conducted a single-centre retrospective observational study analyzing patients with a WCD prescribed at our institution. In total, in 134 patients (mean age 51.7 ± 13.8 ys, 79.1% male) provided with a WCD, arrhythmia recordings were analyzed and categorized as either non-sustained ventricular tachycardia, sustained ventricular tachycardia / fibrillation, and artifact sensing or misclassified episodes. Indication for WCD prescription was both primary and secondary prophylactic. All patients received optimal medical therapy. Baseline evaluation in all patients included transthoracic echocardiography, 12-lead electrocardiogram, and baseline laboratory values.

A total of 3019 false WCD alarms were documented in 134 patients (average number of false alarms 22.5 ± 130.4 episodes per patient) over a mean WCD wearing time of 71.5 ± 70.9 days (daily wearing time 20.2 ± 5.9 hs). In total, in 78 patients (58.2%), either artifact sensing (41.8%), misclassified episodes (3.7%) or both (9.7%) occurred. Misclassified episodes included sinus tachycardias, atrial flutter, atrial fibrillation, ventricular extrasystoles, and intermittent bundle branch block. At multivariate analysis, WCD wearing time (HR 1.02; 95% CI 1.01-1.02; P &lt; 0.001) and loop diuretics (HR 0.16; 95% CI 0.06-0.44; P &lt; 0.001) were identified as independent predictors of artifact episode occurrence. In terms of the frequency of artifact episodes, loop diuretics (HR -0.11; 95% CI interval -0.21-0.0001; P = 0.049), angiotensin receptor-neprilysin inhibitors (ARNIs) (HR -0.11; 95% CI -0.22-0.01; P = 0.03), and the R-amplitude (HR -0.17; 95% CI -0.27-0.07; P = 0.01) of the WCD baseline electrocardiogram (ECG) were independent predictors. In addition, WCD wearing time (HR 1.00; 95% CI 1.00-1.01; P = 0.04), atrial fibrillation (HR 4.03; 95% CI 1.15-14.11; P &lt; 0.001), and ARNIs (HR 3.17; 95% CI 1.05-9.52; P &lt; 0.001) were significantly associated with the occurrence of misdetected / misclassified episodes.

Conclusions

In conclusion, In WCD patients with a ZOLL LifeVest system, false alarms emitted by the device were frequent and most common caused by artefacts.