The Incidence and Prognostic Significance of New-Onset Atrial Fibrillation in Patients With Acute Myocardial Infarction and Left Ventricular Systolic Dysfunction: A CARISMA Substudy
What is the clinical significance of new-onset atrial fibrillation (AF) after discharge from the hospital in patients with an acute myocardial infarction (AMI)?
An implantable loop recorder was implanted in 271 post-AMI patients (mean age 64 years) with an ejection fraction ≤40% and no history of AF. The implantable loop recorders were interrogated every 3 months for 2 years. The primary endpoint was the composite of reinfarction, stroke, heart failure hospitalization, and cardiac death.
The incidence of new-onset AF was 16% at 2 months of follow-up, 32% at 1 year, and 39% at 2 years. Approximately 90% of patients with AF were not symptomatic from the AF. The duration of AF episodes was ≥30 seconds in 56% of patients with AF. New-onset AF was an independent predictor of a primary endpoint event, but only when the AF episodes lasted ≥30 seconds (hazard ratio, 2.73). The risk of a primary endpoint event was not related to the number of episodes of AF recorded during follow-up.
New-onset AF has an incidence of approximately 40% at 2 years in post-infarction patients with left ventricular dysfunction, usually is asymptomatic, and is associated with major cardiovascular events when the duration of episodes is ≥30 seconds.
AF may indeed be an independent predictor of a negative outcome, but it also could be a marker of a confounding variable that was not accounted for in the analysis. Whether prevention of post-infarction AF with a rhythm-control strategy improves prognosis remains to be determined. This seems unlikely based on prior large-scale AF trials such as AFFIRM.
Keywords: Incidence, Prognosis, Myocardial Infarction, Infarction, Follow-Up Studies, Heart Failure, Ventricular Dysfunction, Left, Hospitalization
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