Abnormal constriction or failure of normal dilation of the cardiac microvessels, leading to ischemia with typical ECG changes despite normal coronary arteries on angiography. Chest pain often does not occur with significant exertion but rather with routine daily activities. Associated symptoms include shortness of breath, fatigue, and difficulty with sleep. More common in women with anginal chest pain lasting longer than 10 minutes and more often longer than 30 minutes. Diagnosis is challenging as there are no specific studies to assess cardiac microvasculature.