What are the current guidelines for implantable cardioverter-defibrillator (ICD) placement in patients with various cardiac conditions and risk factors?

ICD Placement Guidelines: Current Recommendations

ICD implantation is definitively indicated for patients with prior cardiac arrest or sustained ventricular tachycardia, and for primary prevention in patients with LVEF ≤35% who are at least 40 days post-MI (or 90 days post-revascularization) and NYHA Class II-III, or LVEF ≤30% with NYHA Class I symptoms, provided they have >1 year expected survival. 1

Secondary Prevention (Strongest Indications)

Class I recommendations - ICD placement is mandatory in:

• Survivors of cardiac arrest due to VF or hemodynamically unstable sustained VT after excluding reversible causes 1
• Patients with structural heart disease and spontaneous sustained VT, whether hemodynamically stable or unstable 1
• HCM patients with previous documented cardiac arrest or sustained ventricular tachycardia 1
• Sustained VT >48 hours post-MI - ICD is reasonable for clinically relevant ventricular arrhythmias occurring >48 hours and within 40 days post-MI 1

Primary Prevention in Ischemic Cardiomyopathy

The 2025 ACC/AHA guidelines provide the most current stratification 1:

LVEF-Based Criteria (all require ≥40 days post-MI, ≥90 days post-revascularization, and >1 year expected survival):

• LVEF ≤30%: ICD indicated for NYHA Class I, II, or III 1
• LVEF 31-35%: ICD indicated for NYHA Class II or III 1
• LVEF ≤40%: ICD indicated if inducible VT on electrophysiologic study 1

Critical timing caveat: Do NOT implant ICDs within 40 days of MI or 90 days of revascularization for primary prevention, as early implantation has not improved survival and may increase non-arrhythmic deaths 1

Primary Prevention in Non-Ischemic Dilated Cardiomyopathy

• LVEF ≤35% with NYHA Class II or III symptoms on optimal medical therapy and >1 year expected survival 1
• Same timing restrictions do not apply as with ischemic cardiomyopathy 1

Hypertrophic Cardiomyopathy (HCM)

The 2020 AHA/ACC HCM guidelines provide specific risk stratification 1:

Class I Indication:

• Prior cardiac arrest or sustained VT 1

Class IIa Indications (reasonable to offer ICD with ≥1 major risk factor):

• Sudden death in ≥1 first-degree or close relative ≤50 years of age definitively attributable to HCM 1
• Massive LVH ≥30 mm in any LV segment 1
• Recent arrhythmic syncope (not vasovagal or LVOTO-related) 1
• LV apical aneurysm, independent of size 1
• LV systolic dysfunction (EF <50%) 1

Risk Assessment Tools:

• For patients ≥16 years: Calculate estimated 5-year sudden death risk using echocardiography-derived left atrial diameter and maximal LVOT gradient during shared decision-making 1
• CMR imaging is beneficial when risk remains uncertain after clinical assessment to evaluate maximum LV wall thickness, EF, LV apical aneurysm, and extent of late gadolinium enhancement 1

Class IIb Considerations:

• Extensive late gadolinium enhancement on CMR or non-sustained VT on ambulatory monitoring in patients without major risk factors may warrant ICD consideration 1

Class III (Do NOT implant):

• HCM patients without risk factors 1
• For the sole purpose of competitive athletics participation 1

Adult Congenital Heart Disease

The 2017 AHA/ACC/HRS guidelines address this complex population 1:

Class I Indications:

• Hemodynamically unstable VT after evaluation and treatment of residual lesions/ventricular dysfunction with >1 year expected survival 1
• Sudden cardiac arrest due to VT/VF without reversible causes with >1 year expected survival 1
• Treat hemodynamic abnormalities FIRST before considering ICD in patients with complex/sustained VA and important residual lesions 1

Class IIa Indications:

• Repaired Tetralogy of Fallot with inducible VT/VF or spontaneous sustained VT with >1 year expected survival 1
• Unexplained syncope with moderate or severe complexity congenital heart disease, moderate ventricular dysfunction or marked hypertrophy - either ICD or EP study with ICD if inducible sustained VA 1

Pediatric Considerations

For children with HCM who have ≥1 conventional risk factors (unexplained syncope, massive LVH, nonsustained VT, or family history of early HCM-related sudden death), ICD placement is reasonable but must weigh the relatively high complication rates of long-term ICD placement in younger patients 1

Critical Exclusions and Contraindications

• Do NOT implant within 40 days of MI for primary prevention (associated with increased non-arrhythmic deaths despite reducing arrhythmic deaths) 1
• Wearable cardioverter-defibrillator has uncertain benefit early post-MI with LVEF ≤35% 1
• Asymptomatic bradyarrhythmias after cardiac transplantation 1
• Patients without >1 year meaningful survival expectation 1

Shared Decision-Making Requirements

Individual clinical judgment is mandatory when assessing prognostic strength of risk markers, with thorough discussion of evidence, benefits, and estimated risks to engage fully informed patient participation 1