Atrial Fibrillation and Death After Myocardial Infarction: A Community Study

Study Questions:

Does atrial fibrillation (AF) after a myocardial infarction (MI) increase the risk of death?

Methods:

The subjects of this community-based study were 3,220 patients hospitalized for acute MI in 1983-2207. Pertinent data were obtained by review of a centralized database of all hospitalizations and outpatient clinic visits.

Results:

There was a history of AF before the MI in 9.4% of patients. During a mean follow-up of 6.6 years, the incidence of new-onset AF was 4.2%/year. The cumulative incidence of AF at 5 years was 19%. AF occurred within 2 days of MI in 30% of patients who developed AF. The risk factors for AF included older age, female gender, hypertension, and diabetes. The mortality rate was 10% at 30 days and 34% at 5 years. Post-MI AF was associated with a higher risk of death, with the extent of excess risk depending on the timing of the AF. AF that occurred >30 days post-MI was associated with a >2-fold higher risk of death, whereas AF within 2 days was associated with a 1.6-fold higher mortality rate and AF at 3-30 days with a 1.8-fold higher mortality rate.

Conclusions:

The authors concluded that new-onset AF after an MI is an independent predictor of mortality, particularly when it occurs >30 days post-infarction.

Perspective:

Prior studies on the prognostic impact of post-infarction AF on survival have had discrepant results. This large-scale, long-term study presents substantial evidence that AF does independently contribute to excess mortality after MI. Because of multiple potential confounding variables, it still is unclear whether the AF is directly responsible for the excess mortality and whether prevention of AF would improve survival.

Keywords: Myocardial Infarction, Confounding Factors (Epidemiology), Follow-Up Studies, Risk Factors, Hospitalization


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