Saito Y, et al. - Because coronary endothelial and circulatory dysfunction plays important roles in the pathogenesis of vasospastic angina (VSA), researchers examined 32 prospectively enrolled VSA patients without obstructive coronary artery disease in the left descending coronary artery, to gain a complete understanding of the entire coronary circulation including microvasculature in these subjects. They performed an invasive assessment of coronary circulation by using a thermodilution method by obtaining the mean transit time (Tmn) at rest and hyperemia, coronary flow reserve, and index of microcirculatory resistance. They found a significantly lower reactive hyperemia index in VSA patients vs those without VSA. VSA patients also had significantly longer resting Tmn. Overall, decreased resting coronary flow and impaired endothelial function were observed in VSA patients.