The following are key points to remember from a state-of-the-art review on revisiting implantable cardioverter-defibrillator (ICD) therapy for primary prevention in patients with heart failure and reduced ejection fraction (HFrEF):

1. The MADIT I and II trials demonstrated a survival benefit with primary prevention ICDs in patients post–myocardial infarction (MI) with left ventricular EF (LVEF) <35% and <30%, respectively, compared to medical therapy. However, trials examining the benefit of ICD in patients recovering from acute MI (AMI) have been negative.
2. Primary prevention of sudden cardiac death (SCD) in nonischemic cardiomyopathy (NICM) patients was shown in the SCD-HeFT trial that enrolled both patients with ICM and NICM, New York Heart Association (NYHA) class II or III, and LVEF ≤35%. However, the recent DANISH trial showed no statistically significant reduction in mortality with ICDs in patients with NICM, but the incidence of SCD was lower in patients receiving an ICD. Secondary analysis of the study showed that ICD was associated with a reduction in all-cause mortality in patients <70 years old. Similarly, a meta-analysis of four trials suggested a 25% reduction in mortality in patients with NICM with an ICD.
3. Current guidelines provide the strongest recommendation (Class I) for ICD to patients with NICM or ICM with LVEF ≤35%, NYHA class II-III, on optimal guideline-directed medical therapy (GDMT), and life expectancy of ≥1 year.
4. ICDs are also recommended (Class I) in patients ≥40 days after an AMI with LVEF <30%, even in the absence of symptoms.
5. Patients with advanced HF with limited life expectancy, including NYHA class IV symptoms, who are not candidates for advanced therapies or have limited survival of <1 year, should not receive an ICD (Class III recommendation).
6. In older patients, the benefits of an ICD may be diminished due to increased comorbidities and reduced life expectancy with an increased risk of device-associated complications. Similarly, data on patients needing an ICD who are on hemodialysis for end-stage renal disease are sparse and current guidelines recommend against this. Similarly, patients with diabetes have a 2.6-fold increased risk for complications from an ICD. Therefore, shared decision making plays an important role in discussions with patients on ICDs.
7. Shared decision making for ICDs should highlight the survival benefit associated with them but also discuss possible complications associated with the device.
8. Trials with ICDs have underrepresented women and non-White individuals. ICDs are underutilized in the general population and this disparity is more pronounced in women and Black patients. Reasons for these disparities include physician bias with trials enrolling predominantly male patients and disparities in access to high-quality care.
9. Pooled data from trials suggest that Black patients with NICM have a higher risk for ventricular and atrial arrhythmias with lower survival rates compared to Whites. This suggests that Black patients with NICM should receive consideration for an ICD for primary prevention, as the DANISH trial did not enroll any Black patients.
10. All components of contemporary GDMT (angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers/angiotensin receptor–neprilysin inhibitors, beta-blockers, mineralocorticoid-receptor antagonists, and sodium-glucose cotransporter-2 inhibitors) reduce mortality and improve morbidity. Therefore, if GDMT can be rapidly initiated and titrated, improvement in LVEF can lead to deferral of ICD implantation.
11. Etiology of cardiomyopathy impacts the risk for SCD as arrhythmogenic cardiomyopathies such as arrhythmogenic right ventricular dysplasia and LMNA-associated disease, and channelopathies. In such populations, ICD indications differ by genetic etiology, and family and clinical history. Additional considerations include scar burden on cardiac magnetic resonance imaging (specifically mid-myocardial late gadolinium enhancement), and patients with extremely low LVEF and severe LV dilatation who may warrant earlier consideration for an ICD.

Clinical Topics: Arrhythmias and Clinical EP, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Heart Failure and Cardiomyopathies

Keywords: Death, Sudden, Cardiac, Defibrillators, Implantable, Heart Failure, Reduced Ejection Fraction, Primary Prevention

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