Air pollution and microplastics pose major public health threats. Emerging data have shown that micro- and nanoplastics (MNPs) are ubiquitous environmental pollutants accumulating in human tissues, triggering inflammation and prothrombotic state. This study will investigate the presence and burden of MNPs within coronary thrombi/thromboaspirate of patients presenting with ST segment elevation acute myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention and their association with cardiac damage, plaque vulnerability, microvascular obstruction, and cardiovascular events. Plaque vulnerability will be explored by optical coherence tomography, while microvascular obstruction will be assessed by bolus thermodilution and cardiac magnetic resonance. Participants will be followed up for 1-year to evaluate whether the presence and the burden of MNPs will be associated with a higher incidence of the cardiovascular events.