Microvascular coronary dysfunction (MCD) (abnormities in small blood vessels/arteries in heart) with symptoms of persistent chest pain impacts women. There are an estimated 2-3 million women in the US with MCD and about 100,000 new cases annually. Autonomic nervous system (ANS) is part of the central nervous system to help people adapt to changes in their environment. It controls what are normally involuntary activities, such as heart rate, respiration (breathing), body temperature, blood pressure, and urinary function. However, there is a limited understanding of the role of ANS in MCD. This research is proposed to investigate cardiovascular reactivity to mental stress and the cardiac (heart) nervous system in women with MCD using mental stress testing, peripheral vascular testing, advanced cardiac imaging and cardiac autonomic function testing. 100 participants will be recruited in the next five years.