At what ejection fraction (EF) level is a wearable cardiac vest considered for patients with heart failure with reduced ejection fraction (HFrEF)?

Wearable Cardiac Vest for HFrEF: EF Thresholds

A wearable cardioverter-defibrillator is recommended for patients with heart failure with reduced ejection fraction (HFrEF) who have an LVEF ≤35% during the high-risk period after myocardial infarction, though evidence shows limited mortality benefit. 1

Definition and Classification of HFrEF

• HFrEF is defined as heart failure with a left ventricular ejection fraction (LVEF) ≤40% according to the 2022 AHA/ACC/HFSA guidelines 1
• Patients with LVEF 41-49% are classified as having HF with mildly reduced EF (HFmrEF) 1
• Patients with LVEF ≥50% are classified as having HF with preserved EF (HFpEF) 1

Wearable Cardioverter-Defibrillator Recommendations

• The wearable cardioverter-defibrillator is primarily considered for patients with recent MI and LVEF ≤35% 1
• This recommendation received a Class IIb, Level of Evidence C classification in the ESC guidelines 1
• The VEST trial studied wearable cardioverter-defibrillators in patients with recent MI and LVEF ≤35%, but did not show a significant reduction in sudden cardiac death 1

Permanent ICD Recommendations for Comparison

• Permanent ICDs are recommended for primary prevention in HFrEF patients with:
  • LVEF ≤35% despite >3 months of optimal medical therapy 1
  • LVEF ≤30% for NYHA class I patients (ACC/AHA Class IB recommendation) 1

Important Considerations and Caveats

• Wearable cardioverter-defibrillators are typically used as a bridge therapy during the waiting period before permanent ICD implantation is considered 1
• Current guidelines recommend against ICD implantation within 40 days after MI due to lack of early benefit shown in clinical trials 1
• The wearable vest is particularly considered during this 40-day waiting period after MI when patients are at high risk but not yet eligible for permanent ICD 1
• Despite their use, the VEST trial results suggest limited mortality benefit, which may lead to downgrading of recommendations in future guidelines 1

Emerging Considerations

• With optimal use of disease-modifying therapies (beta-blockers, MRAs, ARNIs, and SGLT2i), the need and timing for ICD use as primary prevention of sudden death may need reconsideration, especially in non-ischemic HF 2
• The evidence for benefit of prophylactic ICD implantation is stronger for ischemic cardiomyopathy than for non-ischemic causes of HFrEF 2

In summary, wearable cardioverter-defibrillators are primarily considered for patients with HFrEF who have an LVEF ≤35%, particularly during the high-risk period after MI when permanent ICD implantation is not yet recommended.