When should a patient with a history of life-threatening arrhythmias or significant left ventricular dysfunction, such as impaired left ventricular function, consider getting an Implantable Cardioverter-Defibrillator (ICD)?

When to Get an ICD

An ICD is recommended immediately for patients who have survived cardiac arrest due to VT/VF or experienced sustained VT causing hemodynamic compromise, provided reversible causes are excluded and meaningful survival >1 year is expected. 1, 2

Secondary Prevention (Strongest Indication - Class I)

For patients with life-threatening arrhythmias, ICD implantation is the standard of care and reduces arrhythmic mortality by 50% and total mortality by 28% compared to antiarrhythmic drugs. 1

Absolute Indications for ICD:

• Survivors of cardiac arrest due to VT/VF (unless occurring within 48 hours of acute MI with complete revascularization and normal LV function) 3, 1, 2
• Sustained VT causing syncope or hemodynamic compromise 1, 2
• Hemodynamically unstable VT with impaired left ventricular function on optimal medical therapy 1

Critical Timing Consideration:

Even after coronary revascularization, patients who survived cardiac arrest remain at high risk and require ICD unless the event was clearly related to acute MI with complete revascularization and normalization of LV function. 1, 2 The arrhythmogenic substrate persists despite revascularization in most cases. 2

Primary Prevention Based on LVEF

LVEF ≤35% with Heart Failure:

ICD is recommended for patients with LVEF ≤35%, NYHA class II-III heart failure on optimal medical therapy, and expected survival >1 year. 4, 5 This applies to both ischemic and non-ischemic cardiomyopathy. 5, 6

Post-MI with LVEF ≤30%:

ICD is indicated for patients with prior MI and LVEF ≤30% on guideline-directed medical therapy, provided >40 days have passed since the acute event. 4

Important Caveat:

The survival benefit is most pronounced in patients with LVEF 20-34%. 1 However, recent evidence suggests that contemporary heart failure therapies may reduce arrhythmic risk, creating clinical equipoise about routine primary prevention ICD use. 7

Disease-Specific Indications

Cardiac Sarcoidosis (Class I):

ICD is recommended for patients with cardiac sarcoidosis who have sustained VT, survived sudden cardiac arrest, OR have LVEF ≤35%, with expected survival >1 year. 3

For cardiac sarcoidosis patients with LVEF >35% but with syncope and/or myocardial scar on cardiac MRI/PET scan, ICD implantation is reasonable (Class IIa). 3

Adult Congenital Heart Disease (Class I):

ICD is recommended for patients with adult congenital heart disease and hemodynamically unstable VT or sudden cardiac arrest due to VT/VF (absent reversible causes), after evaluation and treatment of residual lesions. 3

For repaired tetralogy of Fallot with inducible VT/VF or spontaneous sustained VT, ICD implantation is reasonable (Class IIa). 3

Hypertrophic Cardiomyopathy:

Sudden death survivors and sustained VT patients with HCM should receive ICDs. 2 A subset with LVEF <50% (end-stage disease) or LV aneurysm warrant ICD consideration. 3

Myocarditis:

For giant cell myocarditis with VF or hemodynamically unstable VT treated with guideline-directed therapy, ICD may be considered if meaningful survival >1 year is expected (Class IIb). 3

Absolute Contraindications (Class III)

Do NOT implant an ICD in patients with: 1, 2

• Terminal illness with life expectancy <6 months
• NYHA class IV drug-refractory heart failure who are not transplant candidates
• Severe neurological sequelae following cardiac arrest
• VT/VF associated with completely reversible causes

Device Selection Algorithm

Before selecting an ICD type, determine if the patient needs: 1

• Bradycardia pacing
• Antitachycardia pacing for VT termination
• Cardiac resynchronization therapy (CRT)

Subcutaneous ICD (Class I):

S-ICD is recommended for patients meeting ICD criteria who have inadequate vascular access or high infection risk, AND do not need pacing for bradycardia, VT termination, or CRT. 3

S-ICD should NOT be implanted (Class III: Harm) if bradycardia pacing, CRT, or antitachycardia pacing is required. 3

Wearable Cardioverter-Defibrillator:

WCD is reasonable (Class IIa) for patients requiring ICD removal due to infection who have history of sudden cardiac arrest or sustained VA. 3

WCD may be reasonable (Class IIb) for patients at increased SCD risk but temporarily ineligible for ICD: 3

• LVEF ≤35% within 40 days of MI
• Newly diagnosed non-ischemic cardiomyopathy
• Within 90 days of revascularization
• Active myocarditis or systemic infection
• Awaiting cardiac transplant

Common Pitfalls to Avoid

Do not withhold ICD from post-revascularization secondary prevention patients based solely on improved LVEF - the arrhythmogenic substrate often persists despite revascularization. 2

Do not assume revascularization eliminates VT/VF risk - the AVID Registry showed similar or worse mortality in "correctable cause" patients treated with revascularization alone. 2

Ensure meaningful survival >1 year is expected - this criterion appears in virtually all ICD recommendations and is essential for appropriate patient selection. 3, 1, 2

Alternative When ICD Unavailable or Refused

If ICD is unavailable, contraindicated, or refused, amiodarone may be considered (Class IIb) for patients with VF/VT and ICD indication. 1

Class Ic antiarrhythmics (flecainide, propafenone) are potentially harmful (Class III: Harm) in patients with structural heart disease and ventricular arrhythmias. 1