Among patients with stable ischemic heart disease who are referred for coronary angiography, a substantial proportion have non-obstructive coronary artery disease (CAD). Ischemia based on symptoms or stress testing may be due to coronary microvascular dysfunction in up to 40% of these patients. However, the mechanisms and optimal treatment of coronary microvascular dysfunction are unknown. Aberrant platelet activity and inflammation have been hypothesized as mechanisms of microvascular dysfunction. Investigators plan to evaluate association between platelet activity, inflammation, and coronary microvascular dysfunction in stable women referred for coronary angiography, and to identify non-invasive correlates of coronary microvascular dysfunction in these patients.

The objectives of this study are to

1. Investigate platelet activity and inflammation in patients with and without coronary microvascular disease who are referred for coronary angiography for the evaluation of stable ischemic heart disease and are found to have non-obstructuve epicardial CAD
2. To identify correlates of coronary microvascular dysfunction in non coronary microvascular beds that can be characterized in vivo.

Inclusion Criteria:

• Adult women age ≥18 years referred for coronary angiography
• Stable ischemic heart disease, defined by ischemic symptoms and/or myocardial ischemia by stress testing
• Administration of aspirin therapy prior to cardiac catheterization

Exclusion Criteria:

Pre-Cath Exclusion criteria:

• Active bleeding and/or bleeding diathesis
• Anemia (hemoglobin <9 mg/dl)
• Known thrombocytosis (platelet count >500,000)
• Know thrombocytopenia (platelet count <100,000)
• NSAIDs (e.g., ibuprofen, naproxen) within 3 days
• Platelet antagonists other than aspirin and thienopyridines, within 7 days
• Prior percutaneous coronary intervention or coronary artery bypass grafting
• Acute myocardial infarction within 3 months
• Severe valvular heart disease
• Cardiogenic shock or mechanical circulatory support
• New York Heart Association (NYHA) Functional Class III or IV heart failure
• Ejection Fraction <40%
• Hypertrophic obstructive cardiomyopathy or severe left ventricular hypertrophy
• Pregnancy
• Contraindication to intravenous infusion of adenosine during coronary angiography, due to known hypersensitivity to adenosine, known or suspected bronchoconstrictive or bronchospastic lung disease (severe asthma), second- or third-degree AV block (except in patients with a functioning artificial pacemaker), or sinus node disease, such as sick sinus syndrome or symptomatic bradycardia,

Angiographic Exclusion criteria:

• Obstructive CAD (≥50% luminal obstruction in ≥1 major epicardial coronary arteries by invasive coronary angiography)
• Unfavorable coronary artery anatomy for guidewire positioning (as determined by the angiographer or PI)