The purpose of this research is to find out if patients with Type 2 Myocardial Infarction (T2MI) without significant epicardial coronary artery disease (CAD) have a greater chance of having coronary microvascular disease (CMD).

Inclusion Criteria:

• Ability to give informed consent
• Structurally normal heart (normal LV and RV function, no more than mild valvular heart disease)
• For controls: atypical chest pain with indication for CMD testing
• For T2MI: meet criteria for T2MI according to the 4th Universal definition of MI (rise/fall of troponin with at least 1 value >99th centile+ evidence of symptoms or signs of myocardial ischemia)

Exclusion Criteria:

• Acute coronary event (evidence of plaque rupture, fissure or dissection on coronary angiogram)
• Known to have angiographically significant CAD/pressure wire positive for epicardial CAD
• Inability to receive heparin products
• Allergy/contraindication to acetylcholine/adenosine/nitroglycerine products
• Prior coronary artery bypass grafting
• Pregnancy (if sexually active woman of reproductive age, need negative pregnancy test prior to proceeding with coronary angiography - this is standard of care in cath lab)
• Asthma with prior ICU admission due to bronchospasm/need for invasive ventilation

Subjects receiving care at Mayo Clinic in Rochester, MN identified with T2MI and controls with atypical chest pain with indication for CMD testing will be enrolled in this study. Both groups will have no epicardial coronary stenosis >50% or obstructive disease.