Implantable ICD vs. Cutaneous (Non-Implantable) ICD: Indications, Risks, and Cost-Effectiveness

By Dr. Abdelwahab Arrazaghi, MD, FABIM, FRCPC

Specialist in Internal Medicine and Cardiovascular Disease

Introduction

Sudden cardiac death (SCD) prevention remains one of the cornerstones of modern cardiology. Since the first implantable cardioverter-defibrillators (ICDs) were introduced, technology has advanced to include transvenous ICDs (TV-ICDs), subcutaneous ICDs (S-ICDs), and the wearable cardioverter-defibrillator (WCD).

Each device has unique strengths, risks, and limitations. Choosing between them depends on indication, pacing needs, infection risk, patient characteristics, and cost-effectiveness. This article summarizes contemporary evidence and guidelines to help clinicians and patients navigate these decisions.

1. Device Overview

Transvenous ICD (TV-ICD):

Generator in the chest with transvenous leads.
Provides defibrillation, anti-tachycardia pacing (ATP), brady pacing, and diagnostics.
Long-standing standard of care, but carries long-term lead-related risks.

Subcutaneous ICD (S-ICD):

Generator and lead implanted entirely under the skin, no venous access required.
Offers defibrillation only — no pacing or CRT.
Comparable efficacy to TV-ICD (PRAETORIAN trial) with fewer lead-related/systemic infections.

Wearable Cardioverter-Defibrillator (WCD):

Vest with external electrodes and monitor.
Provides continuous rhythm surveillance and shock delivery.
A temporary bridge in situations where ICD implantation is deferred or contraindicated (e.g., early post-MI, recent device infection, myocarditis recovery).

2. Guideline-Based Indications

Implantable ICDs (TV-ICD or S-ICD):

Secondary prevention (Class I): Survivors of VT/VF or unstable sustained VT not due to reversible causes.
Primary prevention:
- Ischemic/non-ischemic cardiomyopathy with LVEF ≤35% despite optimal therapy.
- Post-MI (≥40 days) with LVEF ≤30%.
- Select inherited arrhythmia syndromes (HCM, ARVC, long QT, Brugada, etc.) based on risk stratification.

Choosing between S-ICD and TV-ICD:

S-ICD: when pacing is not required, particularly in young patients, high infection risk, or venous access problems.
TV-ICD: when ATP or brady pacing is needed, or when CRT-D is indicated.

Wearable Cardioverter-Defibrillator (WCD):

Bridge strategy only in:
- Newly diagnosed HFrEF or early post-MI during the waiting period.
- Active infection or lead extraction.
- Potentially reversible cardiomyopathy (myocarditis, peripartum, chemotherapy-related).
- Pre-transplant/LVAD evaluation.
Routine post-MI use not supported (VEST trial showed no mortality benefit in intention-to-treat).

3. Effectiveness and Risks

Implantable ICDs:

Proven mortality reduction in both primary and secondary prevention (landmark MADIT-II, SCD-HeFT).
Risks: lead failure, systemic infection, pocket complications, inappropriate shocks.
TV-ICD → higher long-term lead burden.
S-ICD → lower infection/lead risk, but no pacing options.

Wearable ICD (WCD):

VEST trial: no reduction in arrhythmic death overall; benefit suggested only in highly adherent subgroups.
Risks: skin irritation, alarm anxiety, adherence burden (requires ≥20–22 h/day wear).
Real-world data suggest it helps select high-risk patients during transient periods.

4. Special Populations

Recent MI/revascularization: Defer ICD; consider WCD if high risk (very low EF, syncope, scar burden).
Myocarditis/new cardiomyopathy: WCD while awaiting recovery assessment.
Post-extraction infection: WCD as bridge; S-ICD often favored at re-implant to minimize reinfection risk.
Young patients/venous access limitations: S-ICD to avoid intravascular leads.

5. Cost-Effectiveness

Implantable ICDs:

Consistently cost-effective in eligible patients.
ICERs typically $13,000–$35,000/QALY across studies.

Wearable ICDs:

Mixed results — benefit hinges on risk level and adherence.
U.S. models: ~$60,600/QALY.
UK: £23,024/QALY.
Medicare data: ~$12,373 per life-year gained post-MI.
Best value in high-risk, temporary scenarios (e.g., post-extraction, awaiting transplant).

6. Practical Selection Framework

Confirm indication & timing.
- If definitive → implant ICD.
- If transient → consider WCD.
Match device to patient needs.
- TV-ICD: pacing/ATP or CRT needed.
- S-ICD: pacing not needed, infection/lead risk high.
- WCD: short-term bridge while awaiting recovery or re-evaluation.
Discuss trade-offs openly.
- ICDs = long-term proven survival benefit.
- WCD = non-invasive, but only effective if worn consistently.

7. Summary Table

Dimension	TV-ICD	S-ICD	WCD
Core role	Definitive therapy (pacing + defibrillation)	Definitive therapy (defibrillation only)	Temporary bridge
Pacing/ATP	Yes	No	No
Infection/lead risk	Higher	Lower	Minimal (skin irritation only)
Mortality evidence	Strong, multiple RCTs	Comparable outcomes, fewer lead issues	Neutral (VEST ITT); possible benefit with high adherence
Cost-effectiveness	Consistently favorable	Similar to TV-ICD	Condition- and adherence-dependent
Best use cases	Most ICD candidates, CRT-D	Young, infection risk, venous issues	Early post-MI, myocarditis, post-extraction, transplant/LVAD bridge

Conclusion

For patients who clearly meet criteria, implantable ICDs remain the gold standard:

TV-ICD when pacing/CRT is needed.
S-ICD when pacing isn’t required and avoiding leads is preferred.

The wearable ICD fills a narrower role — a time-limited, non-invasive bridge during transient high-risk states or when implantation is temporarily contraindicated. Its value depends on careful patient selection and adherence.

Ultimately, device choice should be guided by guidelines, individual risk, pacing needs, infection considerations, cost-effectiveness, and patient preference — with shared decision-making at the center.