Atrial fibrillation and death after myocardial infarction: a community study

Abstract

Background: Atrial fibrillation (AF) often coexists with myocardial infarction (MI), yet its prognostic influence is disputed. Prior reports studied the relationship of AF during early hospitalization for acute MI to the risk of death and could not address the timing of AF in relation to the MI (ie, before, during, after). Furthermore, as data come mostly from clinical trials, their applicability to the community is uncertain. The aims of our study were to assess the occurrence of AF among MI patients, determine whether it has changed over time, and quantify its impact and the impact of its timing on mortality after MI.

Methods and results: This was a community-based cohort of 3220 patients hospitalized with incident (first-ever) MI from 1983 to 2007 in Olmsted County, MN. Atrial fibrillation was identified by diagnostic codes and ECG. Outcomes were all-cause and cardiovascular death. Atrial fibrillation before MI was identified in 304 patients, and 729 developed AF after MI (218 [30%] within 2 days, 119 [16%] between 3 and 30 days, and 392 [54%] >30 days post-MI). The cumulative incidence of AF after MI at 5 years was 19% and did not change over the calendar year of MI (the incidence of AF was the same regardless of when the MI occurred). During a mean follow-up of 6.6 years, 1638 deaths occurred. AF was associated with an increased risk of death (hazard ratio [95% confidence interval] 3.77 [3.37 to 4.21]), independently of clinical characteristics at the time of MI and heart failure. This risk differed markedly according to the timing of AF, and was the greatest for AF occurring >30 days post MI (hazard ratio [95% confidence interval] 1.63 [1.37 to 1.93] for AF within 2 days, 1.81 [0.45 to 2.27] for AF between 3 and 30 days, and 2.58 [2.21 to 3.00] for AF >30 days post MI).

Conclusions: In the community, AF is frequent in the setting of MI. Atrial fibrillation carries an excess risk of death, which is the highest for AF developing >30 days after MI.

Figure 1

Classification of atrial fibrillation among subjects experiencing a myocardial infarction. Prior AF refers to AF occurring for the first time before the MI. New AF refers to AF detected for the first time during or after the MI. AF, atrial fibrillation; MI, myocardial Infarction.

Figure 2

Time between the first occurrence of atrial fibrillation and myocardial infarction. Figure 2A: The period of observation has been truncated at 10 years. Figure 2B: The period of observation is the first 10 days post-MI. AF, atrial fibrillation; MI, myocardial Infarction.