Evolution of Left Ventricular Ejection Fraction After Acute Myocardial Infarction: Implications for Implantable Defibrillator Eligibility
What is the proportion of patients with reduced left ventricular (LV) function after an acute myocardial infarction (AMI) that reached an LV ejection fraction (EF) >35%, thereby no longer qualifying for implantable cardioverter-defibrillator (ICD) treatment?
Patients admitted for AMI with reduced LVEF (≤40%) were eligible for inclusion. Repeat echocardiographic examinations were performed 5 days, and 1 and 3 months after the AMI. The investigators prospectively included 100 patients with LVEF 31 ± 5.8% after AMI. A multiple logistic regression model was used to examine the value of different baseline characteristics as predictors of LVEF recovery and arrhythmic events.
At 1-month follow-up, 55% had an LVEF >35%. The main improvement in LVEF had occurred by 1 month. The mean difference in LVEF over the next 2 months was small, 1.9 percentage units. During the first 9 weeks, 10% of the patients suffered from life-threatening arrhythmias.
The authors concluded that most patients improve their LVEF after AMI, and in the majority, the improvement could be confirmed after 1 month, implying that further delay of ICD implantation may not be warranted.
The main finding from this study is that among patients with an LVEF ≤40% after an AMI, the majority (55%) show rapid improvement to such extent after 1 month that there is no longer a clear indication for ICD treatment. This may be a potential explanation to the lack of benefit in mortality rates that has been seen with early ICD implantations after AMI. It would be beneficial to determine methodology to predict which patients with reduced LVEF after AMI are not likely to improve, so that ICD treatment may be offered earlier, at a time when the risk of sudden cardiac death is strikingly increased.
Keywords: Myocardial Infarction, Stroke Volume, Death, Sudden, Cardiac, Defibrillators, Implantable, Logistic Models
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