Background The selection of patients for prophylactic ICD therapy after myocardial infarction (MI) remains controversial. We sought to determine the optimal LVEF dichotomy limit for ICD therapy in patients with a history of MI.
Methods and results Data from the placebo arms of 4 randomized trials were pooled to create a cohort of 2828 patients (2206 M, age: 65 ± 11) with reduced left ventricular function after MI. The median left ventricular ejection fraction (LVEF) was 33% (range: 6 - 40%). LVEF significantly predicted mortality. Each 10% reduction in LVEF below 40% conferred a 42% increase in all-cause mortality, a 39% increase in arrhythmic cardiac mortality and 49% increase in non-arrhythmic cardiac mortality over the 2-year period of follow up (p < 0.001 for all modes of mortality). As the LVEF progressively decreased from </= 40% to </= 10%, the data show a "U" shaped relationship between the dichotomy limit for LVEF used and the number of patients that must be treated to prevent 1 arrhythmic death in 2 years. At LVEF of 16% - 20%, more patients are likely to die from arrhythmic than non-arrhythmic cardiac deaths. However, the total number of deaths substantially reduced with lower LVEF.
Conclusion There is a trade-off between the sensitivity and positive predictive accuracy across a range of LVEF and no single dichotomy limit is completely satisfactory. In patients with LVEF </= 10%, ICD therapy was not beneficial as all patients in this subgroup died from non-arrhythmic causes. LVEF alone is not sufficient in selecting most high risk patients for primary ICD therapy and further risk stratification process is needed.
- acute myocardial infarction
- all-cause mortality
- arrhythmic cardiac mortality
- left ventricular ejection fraction
- non-arrhythmic cardiac mortality
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