At what ejection fraction (EF) is a life vest recommended?

Recommendations for Life Vest Use Based on Ejection Fraction

A wearable cardioverter-defibrillator (life vest) is recommended for patients with an ejection fraction ≤35% who are not immediate candidates for permanent ICD implantation, particularly during the waiting period of 40-90 days after myocardial infarction or in patients with newly diagnosed non-ischemic cardiomyopathy during the initial 3 months of medical therapy optimization.

Primary Indications Based on Ejection Fraction

The primary indications for life vest use are:

• EF ≤35% in patients who are not immediate candidates for ICD implantation:
  • Post-myocardial infarction patients during the 40-90 day waiting period 1
  • Newly diagnosed non-ischemic cardiomyopathy during the initial 3 months of medical therapy optimization
  • Patients with EF ≤35% awaiting heart transplantation
  • Patients with temporary contraindications to ICD implantation (e.g., infection)

Evidence Supporting Life Vest Use

The evidence for life vest use is primarily based on observational data and expert consensus rather than robust randomized controlled trials:

• The 2017 AHA/ACC/HRS guideline for management of ventricular arrhythmias assigns a Class IIb (Level of Evidence: C) recommendation for wearable cardioverter-defibrillator use 1
• The benefit appears greatest in patients with EF <30%, with a larger mortality reduction (HR 0.72; 95% CI: 0.65-0.81; p<0.001) compared to those with EF 30-35% (HR 0.83; 95% CI: 0.69-0.99; p=0.04) 1

Important Considerations and Limitations

1. VEST Trial Results: The VEST trial did not show a statistically significant reduction in arrhythmic death with life vest use in post-MI patients with EF ≤35% (relative risk 0.67; 95% CI: 0.37-1.21; p=0.18) 2. However:

   • Per-protocol analyses demonstrated significant reductions in total mortality (p<0.001) and arrhythmic mortality (p=0.001) among compliant patients 3
   • Patient compliance significantly impacts outcomes, with better compliance associated with improved survival 3

2. Compliance Factors: Several factors predict better compliance with the life vest 3:

   • Cardiac arrest during index MI
   • More severe LV dysfunction (EF ≤25%)
   • Presence of diabetes or prior heart failure

3. Transitional Period Risk: The highest risk period for sudden cardiac death is during the waiting period before permanent ICD eligibility:

   • 40-90 days post-MI (when ICDs are contraindicated) 1
   • First 3 months after non-ischemic cardiomyopathy diagnosis during medical therapy optimization

Clinical Decision Algorithm

1. For post-MI patients with EF ≤35%:

   • Prescribe life vest for the 40-90 day waiting period before ICD eligibility
   • Emphasize the importance of compliance (≥18 hours/day wear time)
   • Reassess EF after 40-90 days of optimal medical therapy
   • If EF remains ≤35% despite optimal medical therapy, proceed with permanent ICD implantation

2. For newly diagnosed non-ischemic cardiomyopathy with EF ≤35%:

   • Prescribe life vest during the initial 3 months of medical therapy optimization
   • Reassess EF after 3 months of guideline-directed medical therapy
   • If EF remains ≤35%, proceed with permanent ICD evaluation

3. For patients with temporary contraindications to ICD:

   • Use life vest as a bridge until permanent ICD implantation becomes feasible

Common Pitfalls to Avoid

1. Underutilization: Failing to prescribe life vests for eligible high-risk patients during waiting periods for ICD eligibility
2. Poor compliance monitoring: Not addressing factors that may reduce patient compliance with the device
3. Premature ICD implantation: Implanting ICDs before the recommended waiting period (40-90 days post-MI) when recovery of LV function may still occur
4. Delayed reassessment: Failing to reassess EF at appropriate intervals to determine if permanent ICD is indicated

Remember that the life vest is a temporary bridge to either recovery of LV function or permanent ICD implantation, not a long-term solution for patients with persistently reduced ejection fraction.