Subsequent to the loss of myocardium post-myocardial infarction (MI), the affected ventricle undergoes some dynamic structural and functional changes known as remodeling. Cardiac remodeling progresses into heart failure (HF). In this revolutionized percutaneous coronary intervention (PCI) era, the incidence of post-MI HF due to cardiac remodeling remains high. Current standard therapeutic interventions, for HF, aimed solely at correcting a low cardiac output do not necessarily impede HF progression. Recently, doxycycline was found to have an additional biological effect aside from their antimicrobial actions. From several experimental studies and clinical trials, doxycycline showed MMP inhibition activities that can prevent ventricular remodeling. This study aims to evaluate the role of doxycycline in cardiac remodeling prevention post-MI. Our hypothesis is that a better heart function will be observed in STEMI patients who receive a short period of doxycycline administration post-PCI.

Inclusion Criteria:

• Onset of STEMI <12 hours
• Anterior wall STEMI or Killip grade II-III or LVEF <50%
• Undergoing primary PCI

Exclusion Criteria:

• Signs of infection (clinical judgement plus leukocyte count >15,000)
• STEMI mechanical complication
• Moderate-severe valvular disease
• Allergic to doxycycline
• Refuse to join the trial

The only party who is not masked is the pharmacist