Objective: The impact of blood pressure variability (BPV) on cardiac function has been examined through the prism of congestive heart failure and hypertension, but not in the setting of an acute coronary syndrome (ACS). The aim of this study is to determine the association between in-hospital short-term BPV and the development or aggravation ofheart failure in patients with myocardial infarction (MI). Design and method: A total population of 130 MI patients [82.2% male; mean age: 63.8 years; 71.3% hypertensives, 29.5% with diabetes mellitus (DM), 47.3% with STEMI] underwent 24-h ambulatory BP measurement during hospitalization. At one year a follow-up was scheduled in order to record hospitalizations for heart failure (HF).Additionally, emergency room visits (ERV) were conducted whenever a patient reported NYHA deterioration in order to evaluate cardiac function and optimize treatment. BPV was assessed using the average real variability (ARV) of systolic and diastolic BP.The study population was divided intoa STEMI group and a non-STEMI one. Results: Univariate analysis demonstrated that both ARV SBP (HR, 1.823; CI, 0.212–3.435; p = 0.027) and ARV DBP (HR, 2.515; CI, 0.999–4.060; p = 0.002) were predictors of hospitalization for HF in STEMI patients, but not in the entire population or the NSTEMI group. After multivariate analysis ARV SBP (HR, 1.869; CI, 0.361–3.377; p = 0.016) and ARV DBP (HR, 2.681; CI, 1.227–4.135; p = 0.001) retained their predictive power independently of age, gender, history of HT, DM, low-density lipoprotein (LDL-C) and GFR. Regarding ERV, ARV SBP (HR, 1.730; CI, 0.488–2.971; p = 0.008) and ARV DBP (HR, 1.787; CI, 0.487–3.088; p = 0.008) emerged again as predictors and remained independent using the same multivariate model (HR, 2.3; CI, 1.028–3.572; p = 0.001 and HR, 2.247; CI, 0.842–3.653; p = 0.003 respectively). Conclusions: In the setting of MI, in-hospital ARV was associated with the progression of HF during one-year follow-up. These findingscould suggest a closer monitoring ofSTEMI patients with increased BPV for the proper management of their cardiac function.