What are the indications for Implantable Cardioverter-Defibrillator (ICD) placement?

Indications for Implantable Cardioverter-Defibrillator (ICD) Placement

ICD therapy is indicated for patients with reduced left ventricular ejection fraction (LVEF ≤35%) due to prior myocardial infarction or non-ischemic cardiomyopathy, and for those with life-threatening ventricular arrhythmias regardless of ejection fraction. 1

Primary Prevention Indications

• ICD therapy is indicated in patients with LVEF ≤35% due to prior myocardial infarction (MI) who are at least 40 days post-MI and are in NYHA functional Class II or III 1
• ICD therapy is indicated in patients with non-ischemic dilated cardiomyopathy (DCM) who have an LVEF ≤35% and who are in NYHA functional Class II or III 1
• ICD therapy is indicated in patients with LV dysfunction due to prior MI who are at least 40 days post-MI, have an LVEF ≤30%, and are in NYHA functional Class I 1
• ICD therapy is indicated in patients with nonsustained ventricular tachycardia (VT) due to prior MI, LVEF ≤40%, and inducible ventricular fibrillation (VF) or sustained VT at electrophysiological study 1

Secondary Prevention Indications

• ICD therapy is indicated in cardiac arrest survivors due to VT/VF not due to a reversible cause 1
• ICD therapy is indicated in patients with structural heart disease and spontaneous sustained VT, whether hemodynamically stable or unstable 1
• ICD therapy is indicated in patients with syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiological study 1

Special Populations

Patients with Recent Diagnosis of Non-ischemic Cardiomyopathy (<9 months)

• ICD implantation is generally not recommended within the first 3 months after initial diagnosis of NICM unless other indications are present 1
• ICD can be useful in patients 3-9 months from initial NICM diagnosis with LVEF ≤35% who are unlikely to recover LV function 1
• For patients <9 months from initial NICM diagnosis who require permanent pacing and meet primary prevention criteria, ICD with appropriate pacing capabilities is recommended 1
• ICD implantation is recommended for patients <9 months from initial NICM diagnosis who have sustained or hemodynamically significant ventricular tachyarrhythmias 1

Patients with Hypertrophic Cardiomyopathy (HCM)

• ICD implantation is reasonable for patients with HCM who have one or more major risk factors for sudden cardiac death 1

Patients with Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C)

• ICD implantation is reasonable for prevention of SCD in patients with ARVD/C who have one or more risk factors for SCD 1

Patients with Congenital Heart Disease

• ICD decisions in congenital heart disease patients should not be based solely on ejection fraction but should incorporate multiple risk factors 1

Important Considerations and Caveats

• Patients should be evaluated to exclude any completely reversible causes before ICD implantation 1
• ICD therapy is not indicated within 48 hours of acute MI or during an episode of acute ischemia 1
• Patients with a short life expectancy (≤6 months) are generally not appropriate candidates for ICD implantation 1
• Despite meeting LVEF criteria, many eligible patients do not receive ICDs, with disparities noted particularly among Black patients compared to White patients 2
• While LVEF remains the primary criterion for ICD implantation, it has limitations in sensitivity and specificity for predicting sudden cardiac death risk 3, 4
• Advanced age, impaired renal function, and remote MI (>6 months prior to evaluation) are independent predictors of appropriate ICD therapy 5

Algorithm for ICD Decision-Making

1. Assess if patient has had cardiac arrest, sustained VT, or syncope with inducible VT/VF → If yes, consider ICD for secondary prevention 1
2. If no history of cardiac arrest or sustained VT, assess LVEF:
   • If LVEF ≤35% and ischemic cardiomyopathy (≥40 days post-MI) → Consider ICD 1
   • If LVEF ≤35% and non-ischemic cardiomyopathy (≥3 months from diagnosis) → Consider ICD 1
3. For patients with LVEF ≤35% and recent diagnosis of non-ischemic cardiomyopathy (<3 months):
   • Optimize medical therapy and reassess LVEF before considering ICD 1
   • If permanent pacing is required or sustained ventricular arrhythmias are present → Consider ICD 1
4. For patients with specific cardiomyopathies (HCM, ARVD/C), assess specific risk factors beyond LVEF 1

The evidence strongly supports ICD implantation for both primary and secondary prevention in specific patient populations, with the strongest evidence for those with significantly reduced LVEF and either ischemic or non-ischemic cardiomyopathy 1, 6.