The purpose of this study is to determine the prevalence of plaque disruption and to assess the composition of disrupted plaques in patients with myocardial infarction (MI) and non-obstructive coronary artery disease (CAD) using optical coherence tomography (OCT). Additionally, cardiac magnetic resonance imaging (CMR) will be used to detect myocardial abnormalities, which will be correlated to OCT findings to gain insight into the mechanisms of MI in patients with non-obstructive coronary artery disease (i.e. "open arteries").

In this single center, observational study, patients of both sexes with MI who are referred for cath will be enrolled. Those who have no obstructive CAD on clinically indicated coronary angiography, defined as no stenosis of >50% in any major epicardial vessel, will undergo coronary OCT just after the clinically indicated diagnostic angiogram, and CMR within 1 week, typically within 72-96 hours. Participants will be followed for clinical events for at least 1 year. 20 fully eligble participants will be recruited at NYU Langone Medical Center and Bellevue Hospital Center among a projected 200 enrolled patients.

Inclusion Criteria:

• Acute ischemic symptoms compatible with diagnosis of acute coronary syndrome (ACS) (chest pain or anginal equivalent symptoms at rest or new onset exertional anginal equivalent symptoms)
• Objective evidence of myocardial infarction (either or both of the following): Elevation of troponin to above the laboratory upper limit of normal (ULN) or ST segment elevation of ≥1mm on 2 contiguous ECG leads
• Willing to provide informed consent and comply with all aspects of the protocol
• Age ≥ 21 years

Exclusion Criteria:

• Stenosis ≥50% of any major epicardial vessel on invasive angiography, as determined by the angiographer at the time of clinically ordered cardiac cath.
• History of known obstructive CAD at angiography, including history of percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG)
• Recent use of vasospastic agents, such as cocaine, triptans, ergot alkaloids (≤1 month)
• Alternate explanation for troponin elevation, such as hypertensive urgency, acute exacerbation of heart failure, chronic elevation due to kidney disease, pulmonary embolism, cardiac trauma
• Coronary dissection apparent on angiography
• Excessive coronary tortuosity which, in the opinion of the angiographer, increases the risks of OCT
• eGFR<30 or contraindication to additional contrast needed for OCT in the opinion of the angiographer or treating physician
• Contraindication to MRI (including but not limited to MRI-incompatible metal implants or foreign bodies)
• Pregnancy
• Thrombolytic therapy for STEMI (qualifying event)