Highlights
– The German nationwide SCD‑PROTECT registry enrolled 19,598 patients with newly diagnosed reduced LVEF and showed a substantial early incidence of sustained VT/VF requiring WCD therapy in both non‑ischaemic (6.10 first treatments/100 patient‑years) and ischaemic (8.64/100 patient‑years) cohorts.
– Overall appropriate WCD therapy incidence (all events) was 8.53 and 14.98 events/100 patient‑years for NICM and MI/CAD groups, respectively; inappropriate shocks were rare (0.5%) and total mortality during WCD use was low (0.8%).
– LVEF improved to >35% in ~53% of patients within a mean of 66 days, and only 36.2% proceeded to ICD implantation after the WCD period, suggesting WCD use can provide a protective bridging strategy while allowing recovery and risk re‑assessment.
Background and disease burden
Patients with newly diagnosed reduced left ventricular ejection fraction (LVEF) due to non‑ischaemic cardiomyopathy (NICM) or recent myocardial infarction/coronary artery disease (MI/CAD) face a heightened short‑term risk of sudden cardiac arrest (SCA) from ventricular tachycardia/ventricular fibrillation (VT/VF). Contemporary guidelines recommend optimized guideline‑directed medical therapy (GDMT) and defined waiting periods—typically ≥40 days after MI and ≥3 months for newly diagnosed cardiomyopathy—before considering permanent implantable cardioverter‑defibrillator (ICD) implantation for primary prevention. This creates a high‑risk interval when patients may be exposed to potentially fatal arrhythmias before definitive risk stratification. Wearable cardioverter‑defibrillators (WCDs) have been proposed as a temporary, non‑implantable protective option to bridge patients through this early phase, but real‑world data on effectiveness, safety, and downstream impact on recovery and ICD implantation remain limited.
Study design
SCD‑PROTECT was a nationwide, observational, multicentre registry conducted in Germany enrolling all patients who received a WCD between December 2021 and May 2023 (clinicaltrials.gov NCT06883383). The analysis included 19,598 patients with newly diagnosed reduced LVEF categorized as non‑ischaemic cardiomyopathy (NICM) or MI/CAD. Baseline demographics included mean ages 58.6 ± 13.7 years (NICM) and 64.2 ± 10.6 years (MI/CAD); female representation was 23.8% and 16.3%, respectively. Baseline mean LVEF was 26.9 ± 10.3% in NICM and 28.4 ± 8.0% in MI/CAD. The primary outcome was the incidence of sudden cardiac arrest (SCA) due to sustained VT/VF, operationalized as appropriate WCD‑delivered therapies. Events were reported as incidence rates (events per 100 patient‑years) with 95% confidence intervals. Secondary outcomes included inappropriate WCD treatments, all‑cause mortality, adverse events, adherence to WCD use, heart failure medication patterns, LVEF evolution, and rates of subsequent ICD implantation.
Key findings
Patient cohort and follow‑up
The registry captured a large, contemporary real‑world cohort (n=19,598) receiving a WCD for newly diagnosed reduced LVEF. Follow‑up covered the WCD wearing period, with mean duration until reassessment of LVEF of 65.9 ± 43.8 days.
Primary outcome: appropriate WCD therapy
– Incidence of first appropriate WCD treatment (sustained VT/VF leading to WCD therapy) was 6.10 events per 100 patient‑years (95% CI 5.31–7.00) among NICM patients and 8.64 events per 100 patient‑years (95% CI 7.41–10.05) among MI/CAD patients.
– Considering all appropriate WCD treatments (not only first events), incidence density was 8.53 events/100 patient‑years (95% CI 7.36–9.88) in NICM and 14.98 events/100 patient‑years (95% CI 12.69–17.65) in MI/CAD.
These rates indicate a non‑trivial early arrhythmic event burden in both aetiologies, with numerically higher event density in the ischaemic group.
Fig 1. Medication at hospital discharge with wearable cardioverter-defibrillator. ACE, angiotensin converting enzyme; ARB, angiotensin receptor blocker; ARNI, angiotensin receptor–neprilysin inhibitor; CAD, coronary artery disease; MI, myocardial infarction; MRA, mineralocorticoid receptor antagonist; NICM, non-ischaemic cardiomyopathy; SGLT, sodium–glucose-co-transporter
Figure 3.
Secondary outcomes: LVEF recovery, ICD implantation, mortality, and safety
– LVEF improved to >35% in 53.5% of NICM patients and 51.7% of MI/CAD patients over a mean of ~66 days, showing that a substantial proportion recover systolic function during the initial GDMT optimization period.
– At the end of the WCD wearing period, 36.2% of patients underwent ICD implantation, implying that the majority did not require a permanent device after early reassessment.
– Total mortality during the WCD period was 0.8%.
– Inappropriate shocks were uncommon (0.5% of patients), indicating good specificity of current WCD arrhythmia detection and discrimination algorithms in real‑world practice.
Fig 4. Median (interquartile range) left ventricular ejection fraction comparison in the main populations (non-ischaemic cardiomyopathy, myocardial infarction/coronary artery disease). IQR, interquartile range; LVEF, left ventricular ejection fraction; MI/CAD, myocardial infarction/coronary artery disease; NICM, non-ischaemic cardiomyopathy
Adherence and adverse events
The report describes adherence to WCD use as part of the registry data set; while granular daily wear‑time statistics are not reported here, the low inappropriate shock and low overall mortality rates suggest effective device utilization and clinical oversight across participating centres. Adverse events specific to device wear (skin irritation, discomfort) are not emphasized in the summary, suggesting they were infrequent or manageable, but full adverse event tables should be consulted in the primary manuscript for detailed safety profiling.
Interpretation and comparison with prior evidence
SCD‑PROTECT contributes large‑scale, contemporary observational evidence that the early phase after diagnosis of severely reduced LVEF—whether of ischaemic or non‑ischaemic aetiology—is associated with a measurable risk of sustained VT/VF. The incidence rates reported translate to clinically meaningful absolute risks over the typical waiting periods used in guideline recommendations.
These findings should be considered alongside randomized clinical trial data. The VEST trial (Olgin et al., NEJM 2018) investigated WCD use after myocardial infarction and did not demonstrate a statistically significant reduction in arrhythmic death in the primary intention‑to‑treat analysis, but adherence issues and cross‑overs complicated interpretation; per‑protocol analyses suggested possible benefit. SCD‑PROTECT, as a large observational cohort, offers complementary real‑world information on event rates, device performance, and downstream recovery that can inform shared decision‑making in routine practice.
Clinical implications
– Bridging therapy: The WCD appears to offer an effective and safe bridging option during the early GDMT optimization period, protecting patients from potentially fatal arrhythmias while allowing time for myocardial recovery and LVEF reassessment.
– Avoiding unnecessary ICD implantation: With approximately half of patients recovering to an LVEF >35% within ~2 months and only ~36% ultimately receiving an ICD, WCD use may reduce unnecessary permanent device implantation and its long‑term costs and complications.
– Risk across aetiologies: The comparable recovery rates and measurable arrhythmic risk in both NICM and MI/CAD support considering WCD protection irrespective of aetiology when patients present with markedly reduced LVEF in the early phase.
– Low inappropriate therapy rate: The observed 0.5% inappropriate shock rate addresses a common concern about WCD harm from inappropriate shocks; in this registry, such events were uncommon.
Strengths and limitations
Strengths
– Size and scope: This is a very large, nationwide cohort capturing real‑world WCD use across multiple centres, improving generalizability within the German healthcare setting.
– Contemporary practice: Enrollment from 2021–2023 reflects modern GDMT and device technology.
– Clinically meaningful endpoints: Use of WCD‑delivered therapy as a proxy for life‑threatening VT/VF events provides direct, device‑verified outcome data.
Limitations
– Observational design: Without a randomized comparator (no‑WCD group), causal inference about WCD efficacy versus no WCD is limited; confounding by indication and centre‑level practice patterns may influence both outcomes and decisions about ICD implantation.
– Selection bias: Patients selected to receive a WCD may differ systematically (comorbidity, access to care, clinician judgment) from those who did not, which could affect event rates and outcomes.
– Follow‑up window: The primary focus is the WCD wearing period; longer‑term arrhythmic and survival outcomes beyond the bridging period are not addressed here.
– Detail granularity: Adherence metrics, daily wear time, precise device programming parameters, and detailed adverse event reporting are not fully described in the summary and should be reviewed in the complete publication for comprehensive safety assessment.
Expert commentary and guideline context
Current heart failure guidelines recommend waiting periods after MI and for newly diagnosed cardiomyopathy to allow for medical therapy optimization before implanting a permanent ICD for primary prevention. The SCD‑PROTECT data reinforce the clinical dilemma these waiting periods create and provide contemporary evidence supporting the potential role of WCDs as a protective bridge. Clinicians should weigh individual patient risk (arrhythmic risk markers, symptoms, comorbidities), likely probability of LVEF recovery with GDMT, and patient preferences when considering WCD prescription.
Randomized trial data (e.g., VEST) remain important for definitive efficacy assessment, but SCD‑PROTECT’s real‑world registry adds complementary safety and event‑rate information that can inform practice in settings where WCD availability, cost, and patient adherence are real constraints.
Conclusions and practical takeaways
The SCD‑PROTECT registry documents a substantial early incidence of sustained VT/VF requiring therapy in patients with newly diagnosed reduced LVEF of both ischaemic and non‑ischaemic aetiologies. WCDs provided arrhythmic protection with a low rate of inappropriate shocks and low short‑term mortality while nearly half of patients experienced meaningful LVEF recovery, avoiding immediate ICD implantation in many. In clinical practice, the WCD can be considered as a temporary protective strategy during the early GDMT optimization period for selected high‑risk patients, with individualized assessment of risk, expected recovery, and likely adherence.
Important open questions include the comparative effectiveness of WCD versus no WCD in contemporary cohorts with high‑intensity GDMT, cost‑effectiveness across different healthcare systems, and optimal patient selection criteria to maximize net clinical benefit. Prospective randomized trials with robust adherence support and contemporary device algorithms would further clarify the role of WCDs.
Funding and clinicaltrials.gov
The SCD‑PROTECT study is registered at clinicaltrials.gov (NCT06883383). For detailed funding sources and conflict‑of‑interest statements, readers should consult the original publication (Duncker et al., Eur Heart J 2025).
References
1) Duncker D, Marijon E, Metra M, Piot O, Fudim M, Siebert U, Frey N, Maier LS, Bauersachs J. Sudden cardiac death in newly diagnosed non‑ischaemic or ischaemic cardiomyopathy assessed with a wearable cardioverter‑defibrillator: the German nationwide SCD‑PROTECT study. Eur Heart J. 2025 Nov 14;46(43):4597‑4606. doi: 10.1093/eurheartj/ehaf668 IF: 35.6 Q1 . PMID: 40879135 IF: 35.6 Q1 ; PMCID: PMC12614993 IF: 35.6 Q1 .
2) Olgin JE, Pletcher MJ, Vittinghoff E, et al. Wearable Cardioverter–Defibrillator after Myocardial Infarction (VEST). N Engl J Med. 2018;379:1205‑1215. (VEST randomized trial assessing WCD after MI).
3) McDonagh TA, Metra M, Adamo M, et al. 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J. 2021;42(36):3599‑3726. (Guideline statements on GDMT and timing of ICD implantation).
Article provenance
This article is a critical synthesis and interpretation of the SCD‑PROTECT publication and contextual literature intended for clinicians and clinician‑scientists to aid evidence‑based decision‑making.