The ET-1 value was similar in the two groups, but this correlation might be explained by the more diffuse location of endothelial dysfunction in patients with microvascular involvement, compared to those with atherosclerotic lesions, where the alterations are more localized and are limited to a certain coronary territory, and a correlation with systolic dysfunction in these patients would require a more extensive endothelial dysfunction, therefore a much higher ET-1 level. Here, EDN1 is linked to endothelial dysfunction.