What is the purpose of a cardiac life vest (CLV) in patients with high risk of sudden cardiac arrest?

Purpose of a Cardiac Life Vest

A cardiac life vest (wearable cardioverter-defibrillator) is primarily used to protect patients at high risk for sudden cardiac death who are not immediate candidates for an implantable cardioverter-defibrillator (ICD), providing temporary protection against life-threatening ventricular arrhythmias. 1

Primary Indications

The American College of Cardiology/American Heart Association/Heart Rhythm Society guidelines recommend wearable cardioverter-defibrillators in the following situations:

1. Temporary protection after ICD removal:

   • In patients with an ICD and history of sudden cardiac arrest or sustained ventricular arrhythmia who require ICD removal (typically due to infection) 1
   • Provides continuous protection until a new ICD can be implanted 1

2. Temporary protection in high-risk periods:

   • For patients at increased risk of sudden cardiac death who are not yet eligible for an ICD, including:
     • Patients within 40 days after myocardial infarction with LVEF ≤35% 1, 2
     • Patients with newly diagnosed non-ischemic cardiomyopathy 1
     • Patients within 90 days of coronary revascularization 1
     • Patients with myocarditis or secondary cardiomyopathy 1
     • Patients with systemic infection 1
     • Patients awaiting heart transplantation 1, 2

Device Functionality and Effectiveness

The wearable cardioverter-defibrillator:

• Continuously monitors the heart rhythm for life-threatening ventricular arrhythmias
• Delivers a shock to restore normal rhythm when ventricular tachycardia or fibrillation is detected
• Has demonstrated a first shock efficacy of 99% with 90% post-shock survival in registry data 2
• Has a relatively low inappropriate shock rate of approximately 2% 2

Clinical Evidence

The evidence supporting wearable cardioverter-defibrillator use is mixed:

• The WEARIT/BIROAD study showed that 75% of defibrillation attempts were successful, with a low rate of inappropriate shocks (0.67% per month) 3
• However, the VEST trial, which studied post-MI patients with reduced ejection fraction, did not show a statistically significant reduction in arrhythmic death compared to standard medical therapy (1.6% vs 2.4%, relative risk 0.67,95% CI 0.37-1.21) 4
• Real-world data suggests high adherence (median 23.1 hours/day) and effectiveness in terminating ventricular arrhythmias when worn properly 5

Important Considerations

1. Patient adherence is critical:

   • The device should be worn continuously (24 hours/day) except during bathing or showering 2
   • Deaths have occurred in patients not wearing or incorrectly wearing the device 3, 5

2. Temporary solution:

   • The wearable cardioverter-defibrillator is intended as a bridge to:
     • ICD implantation
     • Heart transplantation
     • Recovery of cardiac function
     • Determination of long-term risk

3. Reassessment:

   • Regular reassessment of cardiac function and arrhythmia risk is essential
   • In many cases, left ventricular function improves, eliminating the need for permanent ICD implantation 6

Contraindications

The wearable cardioverter-defibrillator should not be used in patients who require:

• Bradycardia pacing
• Cardiac resynchronization therapy
• Antitachycardia pacing for VT termination 1

In these cases, a traditional implantable device would be more appropriate.