Wearable Cardioverter Defibrillators in Primary Prevention of Sudden Cardiac Death: Insights from a Monocentric Observational Study

Background

The wearable cardioverter defibrillator (WCD) has emerged as a possible device for individuals at transiently increased risk of sudden cardiac death (SCD) who are not immediate candidates for permanent implantable defibrillators (ICDs). While current European guidelines recommend WCD use for secondary prophylaxis, German, American and Italian Guidelines allow its use for primary prevention although the recommendations still underscore uncertainty in its usefulness and efficacy. This study aims to address this gap by evaluating the prescription patterns and outcomes of WCD use in a real-world cohort, with a specific focus on primary prevention across different types of cardiopathy.

Methods

At Klinikum Fürth (Fürth, Germany), a total of 132 consecutive patients received a WCD between 2020 and 2024. This retrospective analysis categorized patients based on the indication for WCD (primary vs. secondary prophylaxis) and the underlying cardiopathy type. Outcomes and alarms during and at the end of the WCD wearing period were assessed using the Zoll network system, and statistical analyses, including Chi-square tests and standardized residuals, were performed to identify significant differences in WCD indications and outcomes across cardiopathy types.  

Results

Our analysis revealed significant variability in WCD prescription practices. Notably, in the primary prescription there was a quite equal distribution of dilated and ischemic cardiopathy whereas the latter was the dominant secondary prevention indication.  The EF was significantly severely reduced in the primary vs secondary prevention group (mean ± SD 31.2±11.5 vs 46.7 ±15.5 %).

In the primary prevention group 2.7% patients experienced an appropriate WCD Therapy and 22 patients out of 83 (26%) with known follow up were finally implanted with a permanent ICD. 

Regarding the outcomes and follow up of patients receiving the WCD either as primary or secondary prophylaxis, a Chi-square analysis showed a significant association between the indication for WCD use and subsequent ICD implantation (p-value: 0.035).

Conclusion

Although lower than in the secondary prevention group, the high number of WCD interventions in the primary prevention group indicates a clinically relevant life-saving effect of the WCD in a population having an increased high risk for SCD not known to be whether permanent or transient at that point of time. This group of patients is actually not covered from European Guidelines. On the other side only one fourth of patients in the primary prevention group was finally implanted with a permanent ICD, because of persisting high arrhythmic risk beyond the WCD wearing period. 

In the Era of modern medical therapy for heart failure this study underlines the need for future research aiming to refine the criteria for WCD prescription in order to optimize the prevention of SCD across all cardiopathy types, ensuring that also temporarily high-risk patients could receive appropriate and timely therapy intervention.