The impact of atrial fibrillation on the prognosis of myocardial infarction is still the subject of debate. We analyzed the influence of previous and new-onset atrial fibrillation on in-hospital and long-term prognosis in patients with acute myocardial infarction.

Prospective study of 1265 patients with ST-segment elevation acute myocardial infarction (military hospitals of Algiers and Constantine). We studied all-cause in-hospital and long-term mortality (median 4.2 years) using adjusted models.

In total, 4.5% of patients had previous atrial fibrillation and 10.6% had new-onset atrial fibrillation. In general, both groups of patients had a high baseline risk profile and an increased likelihood of in-hospital complications. The crude in-hospital mortality rate was higher in patients with previous atrial fibrillation than in those with new-onset atrial fibrillation (22% vs 12%; P<.001; 30% vs 10%; P<.001). The long-term mortality rate was 11.11/100 patient-years in patients with previous atrial fibrillation and 5.35/100 patient years in those with new-onset atrial fibrillation (both groups, P<.001). New-onset fibrillation alone (odds ratio=1.55; 95% confidence interval, 1.08-2.22) was an independent predictor of in-hospital mortality. Previous atrial fibrillation (hazard ratio=1.24; 95% confidence interval, 0.94-1.64) and new-onset atrial fibrillation (hazard ratio=0.98; 95% confidence interval, 0.80-1.21) were not independent predictors of long-term mortality.

New-onset atrial fibrillation during hospitalization is an independent risk factor for in-hospital mortality in acute myocardial infarction.