This is an interventional, prospective, multicenter study (5 IRCCS hospitals belonging to the Italian Cardiology Network) in patients with STEMI treated with successful primary PCI to assess the ability of coronary physiology parameters measured soon after recanalization to predict myocardial tissue characterization assessed with cardiac magnetic resonance (CMR) within a week of the acute event. Furthermore, patients will be followed up for a period of 12 months to assess the incidence of major adverse cardiovascular events (death, death from cardiovascular causes, re-infarction, new coronary revascularization interventions, development of heart failure) based on their stratification according to coronary physiology parameters.

In the present study the investigators will enroll consecutive patients with STEMI acute myocardial infarction treated with successful primary PCI, to assess the ability of coronary physiology parameters, i.e. coronary flow reserve (CFR) and index of microvascular resistance (IMR) measured after recanalization to predict myocardial tissue characterization (MVO, MSI, IS, T2-rt, T1-rt and ECV) assessed with contrast CMR within a week of the acute event. Furthermore, the relationship between left ventricular end-diastolic pressure and of coronary physiology parameters will be evaluated.

Inclusion Criteria:

• Patients with STEMI (defined according to ESC Guidelines 2017), with symptom onset within 12 hours (Class I), or between 12 and 48 hours (Class IIa), (1) successfully treated with primary PCI. (1)

Exclusion Criteria:

1. Patients with previous myocardial infarction in the territory of the infarct-related artery;

2. Patients with previous coronary artery bypass grafting;

3. Patients with cardiogenic shock at presentation;

4. Patients with need for mechanical support of the circulation;

5. Patients with known severe aortic stenosis / insufficiency;

6. Patients with known cardiomyopathy;

7. Patients with malignant neoplasm or systemic pathology with a "quoad vitam" prognosis of less than 1 year;

8. Patients affected by known active infectious diseases;

9. Women who are pregnant or breastfeeding;

10. Patients who are unable to express valid informed consent upon enrollment;

11. Patients with hypersensitivity to the active ingredients used for the study of coronary physiology (nitrates and adenosine);

12. Patients with specific contraindications to cardiac magnetic resonance imaging, including:

    • Patients with allergies and / or with other specific contraindications to the use of paramagnetic contrast media (gadolinium), including chronic renal failure with glomerular filtrate (eGFR) <30 mL / min;
    • Patients with non-resonance-compatible devices or who have undergone previous surgical interventions with placement of non-resonance-compatible vascular clips;
    • Claustrophobic patients.