Sudden cardiac death risk after myocardial infarction across the spectrum of left ventricular ejection fraction: a meta-analysis.
BACKGROUND AND OBJECTIVES Implantable cardioverter defibrillator (ICD) therapy is indicated following a myocardial infarction (MI) to curtail the risk of sudden cardiac death (SCD) in patients who are classified as high-risk, defined by a left ventricular ejection fraction (LVEF) ≤35%. The understanding of risk in patients with ischaemic injury who do not meet these criteria is limited. This study aims to assess the burden of SCD in patients' post-MI with LVEF 36-50%. METHODS Articles reporting mortality and SCD outcomes for participants with LVEF 36-50% post-MI without additional risk stratification or intervention were included. Medline, Embase and Cochrane databases were searched from index entries until the present. Data were synthesised using a random-effects model. Competing risk adjusted number needed to treat (NNT) for ICD implantation was calculated. This study adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. RESULTS 7435 records were identified, five studies with 9345 patients were included. The pooled annual rate of SCD in patients with LVEF 36-50% post-MI was 1.74% (95% CI 1.02 to 2.95); a higher annual rate of 6.34% was observed for LVEF≤35% (p=0.03) while a lower yearly rate of 0.55% was observed for LVEF >50% (p=0.02). The proportion of mortality due to SCD was similar across all LVEF strata (p=0.79). Very high between-study heterogeneity was observed (I2=89.9% for SCD and I2=96.8% for all-cause mortality). During exploratory modelling, the primary prevention ICD NNT for patients with LVEF 36-50% was 19 when applying the MADIT-II ICD treatment effect (HR 0.33, 95% CI 0.20 to 0.53) and extrapolation to a 5-year device lifespan. CONCLUSION This is the first meta-analysis reviewing post-MI patients with LVEF 36-50%. These findings highlight a clinically relevant unmet need for patients who carry a substantial burden of SCD despite being outside current ICD eligibility criteria. Further study is needed to improve risk stratification within this population and determine whether suitable intervention is beneficial. PROSPERO REGISTRATION NUMBER CRD42024551830.