RESUMEN
INTRODUCTION: Oral â-blockers improve the prognosis of patients with acute myocardial infarction, while atrial fibrillation worsens the prognosis of this population. The reduction of atrial fibrillation incidence in patients treated with â-blockers could at least in part explain the benefits of this drug. OBJECTIVE: To investigate the effect of â-blockers on the incidence of atrial fibrillation in patients with acute myocardial infarction. METHODS: We analyzed 1401 patients with acute myocardial infarction and evaluated the occurrence or absence of atrial fibrillation, the use of oral â-blockers and mortality during the first 24 hours. RESULTS: a) The use of â-blockers was inversely correlated with the presence of atrial fibrillation (ñ = 0.004; OR = 0.54). b) Correlations with mortality were as follows: 31.5 percent in patients with atrial fibrillation, 9.2 percent in those without atrial fibrillation (ñ < 0.001; Odds Ratio = 4.52), and 17.5 percent in patients not treated with â-blockers and 6.7 percent in those who received the drug (ñ < 0.001; OR = 0.34). c) Adjusted Models: The presence of atrial fibrillation was independently correlated with mortality (OR = 2.48, ñ = 0.002). The use of â-blockers was inversely and independently correlated with mortality (OR = 0.53; ñ = 0.002). The patients who used â-blockers showed a lower risk of atrial fibrillation (OR = 0.59; ñ = 0.029) in the adjusted model. CONCLUSION: The presence of atrial fibrillation and the absence of oral â-blockers increased in-hospital mortality in patients with acute myocardial infarction. Oral â-blockers reduced the incidence of atrial fibrillation, which might be at least partially responsible for the drug's benefit.