Background: Acute heart failure (AHF), occurring as a complication of ongoing acute myocardial infarction (AMI), is a common predictor of worse clinical outcome. Much less is known about the unique subpopulation of patients who present these two life-threatening conditions in the emergency department (ED).

Aim: The aim of the study was to establish the prevalence of coexistence of AHF with AMI in the ED, to identify clinical factors associated with the higher prevalence of AHF at very early onset of AMI, and to assess the prognostic impact of the presence of AHF with AMI.

Methods: A prospective study of 289 consecutive patients (mean age: 68 ± 11 years, 61% men) admitted to our institution (via the ED) with the diagnosis of AMI between May and October 2012 and followed-up for 2.5 years.

Results: Acute heart failure was diagnosed in 13% of patients in the ED. In multivariable analysis, female sex, chronic obstruc­tive pulmonary disease, and chronic kidney disease significantly increased the risk of developing AHF together with AMI (all p < 0.05). Patients with AHF were hospitalised for longer (9.2 ± 6.1 vs. 6.3 ± 4.5 days, p < 0.001), had higher in-hospital cardiovascular mortality (8% vs. 0%, p < 0.001), and all-cause (34% vs. 15%, p = 0.004) and cardiovascular mortality (26% vs. 9%, p = 0.002) during long-term follow-up.

Conclusions: Despite good logistic- and evidence-based treatment, AHF is present in one in eight patients with AMI at the time of admission to the ED. Particularly poor outcomes characterise critically ill patients; therefore, great effort should be undertaken to improve their care.