Survival of the Fittest
Evolution of Left Ventricular Ejection Fraction After Acute Myocardial Infarction
Sudden cardiac death (SCD) resulting from cardiac arrest remains the leading cause of cardiovascular mortality worldwide and accounts for ≈250 000 deaths annually in the United States.1–4 The majority of cardiac arrests occur in patients with a prior myocardial infarction (MI) at a rate ≈5 times that of the general population.3 Studies evaluating the time dependence of mortality immediately after an MI have consistently demonstrated that the greatest risk for SCD is in patients with impaired left ventricular (LV) ejection fraction (LVEF).1–4 Despite revascularization and widespread use of β-blockers, angiotensin-converting enzyme inhibitors, statins, and antiplatelet agents, the risk of SCD remains highest in the first 30 days in these patients.1–4 On the basis of these observations, strategies for the prevention of SCD need to be implemented early after an MI in high-risk patients.
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Although depressed LVEF identifies patients with increased mortality risk immediately after MI and is widely used as a risk stratification tool, it does not allow a distinction between those who will die of an arrhythmia and those who will die of other cardiovascular causes.4–8 Variable and unpredictable recovery of LV function after MI has consistently been noted immediately after an MI.5–7 Improvement in LVEF commonly begins within 3 days in patients who are revascularized with myocardial stunning and improved function of viable myocardium as the mechanisms.5–7 In the contemporary era of primary percutaneous coronary intervention for MI, of all revascularized patients with LVEF ≤40% at day 3, 24% will improve to have an LVEF ≥40% at 6 months.5–7 Other noninvasive and invasive risk stratification techniques used alone or in combination with the LVEF also …