Primary-prevention ICD after anterior myocardial infarction: case discussion

Presentation

Practice case (not a real patient). A 64-year-old man had an anterior myocardial infarction (MI) 5 weeks ago, treated with primary percutaneous coronary intervention with complete revascularization on the day of the MI. His pre-discharge left ventricular ejection fraction (LVEF) was 30%. He has no documented ventricular arrhythmia since the first 48 hours. He is in sinus rhythm with a QRS duration of 100 ms.^[7][1]

Step 1 — Is an implantable cardioverter-defibrillator (ICD) indicated now?

Discussion:

• No. The 2026 European Society of Cardiology (ESC) heart failure guideline does not recommend a primary-prevention ICD within 40 days of an MI, as implantation during this period does not improve prognosis (Class III, Level B1); at 5 weeks he is inside that window.^[1]
• The two randomized, open-label trials that ESC 2026 cites for this row were DINAMIT (ICD versus no ICD 6 to 40 days after MI in patients with LVEF 0.35 or less and impaired cardiac autonomic function; mean follow-up 30 months; overall mortality hazard ratio 1.08) and IRIS.^[17][18][1]
• IRIS, a randomized, open-label trial, enrolled patients 5 to 31 days after MI who met criterion 1 (LVEF 40% or less and a heart rate of 90 beats per minute or more on the first available electrocardiogram), criterion 2 (NSVT of 150 beats per minute or more on Holter monitoring) or both criteria, and randomly assigned them to an ICD or medical therapy alone; over a mean of 37 months overall mortality was not reduced (hazard ratio 1.04).^[18]
• The 2025 American College of Cardiology/American Heart Association (ACC/AHA) acute coronary syndrome (ACS) guideline recommends an ICD to reduce death in selected post-MI patients with LVEF 40% or less (its Table 17), at least 40 days post MI and at least 90 days postrevascularization (COR 1, LOE A); at 5 weeks after both the MI and the revascularization, he is short of both thresholds.^[4]

Step 2 — Would a wearable defibrillator help in the meantime?

Discussion:

• VEST randomized (2:1) 2302 patients with acute MI and an ejection fraction of 35% or less to a wearable cardioverter-defibrillator (WCD) plus guideline-directed therapy or guideline-directed therapy alone; arrhythmic death at 90 days was 1.6% with the WCD versus 2.4% without (relative risk 0.67, P=0.18).^[23]
• ESC 2026 has a WCD row: a wearable cardioverter-defibrillator may be considered in patients with HF who are at risk of sudden cardiac death for a limited period in order to increase survival as a bridge to decision for permanent ICD implantation or while listed for heart transplantation (Class IIb, Level C).^[1]
• ESC 2026 text adds that a wearable defibrillator may be considered in patients deemed at especially high risk of SCD or as a bridge to decision for ICD implantation, although no mortality benefit has been shown in RCTs.^[1]
• The earlier ESC 2022 guideline (dated) stated that, based on the available data, its task force did not recommend routine use of the WCD in the early post-MI phase, but that the device may be considered in selected post-MI patients deemed to be at high risk for SCD; its Recommendation Table 15 row said the WCD may be considered in the early phase after MI in selected patients (Class IIb, Level B).^[2]
• The 2023 ESC ACS guideline, later than ESC 2022, has the row: ICD implantation or the temporary use of a wearable cardioverter defibrillator may be considered <40 days after MI in selected patients (incomplete revascularization, pre-existing LVEF dysfunction, occurrence of arrhythmias >48 h after STEMI onset, polymorphic VT or VF) (Class IIb, Level C).^[7]
• For patients with HF, the later ESC 2026 HF row is a Class III row against a primary-prevention ICD within 40 days of an MI, and its WCD row is the one given above.^[1]
• The 2025 ACC/AHA ACS guideline says the usefulness of a temporary WCD early after MI is uncertain in patients with an LVEF of 35% or less, to improve survival (COR 2b, LOE B-R).^[4]

Step 3 — Reassessment

Discussion:

• The 2023 ESC ACS guideline recommends repeat evaluation of the LVEF 6–12 weeks after an ACS (and after complete revascularization and the institution of optimal medical therapy) in patients with pre-discharge LVEF 40% or less, to assess the potential need for a primary-prevention ICD (Class I, Level C).^[7]
• ESC 2026 text (no class or level given) calls a 3-month period after uptitration of foundational medical therapy (FMT) before considering ICD implantation reasonable.^[1]
• At 4 months after the MI and the revascularization, after 3 months of optimal FMT, his LVEF is 29%. He has New York Heart Association (NYHA) class II symptoms and is expected to survive longer than 1 year with good functional status.^[1][4]

Step 4 — The decision

Discussion:

• ESC 2026: an ICD is recommended in symptomatic heart failure with reduced ejection fraction (HFrEF), NYHA class II/III, of ischaemic aetiology (unless there was an MI in the prior 40 days), with LVEF ≤35% despite ≥3 months of optimal FMT, provided survival longer than 1 year with good functional status is expected, to reduce the risk of sudden death and all-cause death (Class I, Level B1); he now meets every condition.^[1]
• 2025 ACC/AHA ACS: he is now at least 40 days post MI and at least 90 days postrevascularization, and LVEF 30% or less with NYHA class II is a Table 17 category (all patients should have an expected survival of 1 year or more), so an ICD is recommended for selected patients like him, to reduce death (COR 1, LOE A).^[4]
• MADIT-II is the matching trial: prior MI and LVEF 0.30 or less, randomized 3:2 to a defibrillator or conventional medical therapy, hazard ratio 0.69 for death from any cause over an average of 20 months.^[14]
• The 2025 ACC/AHA ACS guideline describes the MADIT II patients as at least 30 days after MI or 3 months after revascularization for MI; at 4 months he is past both.^[4]
• The dated NHFA/CSANZ 2018 guideline agrees in direction: an ICD should be considered for primary prevention at least 1 month following MI with LVEF 30% or less, to decrease mortality (Strong recommendation FOR; high quality of evidence).^[9]

Step 5 — Counselling

Discussion:

• ESC 2026 calls shared decision-making essential when considering ICD implantation in patients with heart failure, with individualized information on the potential risks and benefits to support an informed decision.^[1]
• ESC 2026 states that an ICD commits the patient to lifelong monitoring and generator replacements, and that the lifelong risk of complications should be considered in the decision to implant.^[1]
• ESC 2026 states that delaying ICD implantation carries a risk of SCD of 2%–4% by 6 months and ∼7% by 1 year.^[1]

Marking (Pass/Fail)

• Pass: withholds the ICD within 40 days of the MI with the ESC 2026 Class III row and the results of DINAMIT (randomized, ICD versus no ICD 6 to 40 days after MI with LVEF 0.35 or less and impaired cardiac autonomic function; mean 30 months) and IRIS (randomized, ICD versus medical therapy alone, enrolled 5 to 31 days after MI with either LVEF 40% or less and a heart rate of 90 beats per minute or more on the first available electrocardiogram, or NSVT of 150 beats per minute or more on Holter monitoring, or both; mean 37 months), in which overall mortality did not fall with an ICD.^[1][17][18]
• Pass: with pre-discharge LVEF 40% or less, reassesses LVEF 6–12 weeks after the ACS, after complete revascularization and optimal medical therapy, under the 2023 ESC ACS row, and applies the 2025 ACC/AHA ACS row for selected patients with LVEF 40% or less (Table 17) at least 40 days post MI and at least 90 days postrevascularization.^[7][4]
• Pass: states every condition of the ESC 2026 ischaemic row before recommending the ICD.^[1]
• Fail: implants at 5 weeks, or presents the WCD as proven to reduce arrhythmic death.^[1][23]