EDN1 and Tako-tsubo cardiomyopathy: In a study, ET-1 levels in blood plasma were twofold higher than in healthy volunteers, a signature of circulating microRNAs differentiates takotsubo cardiomyopathy from AMI; however, other investigators claim no differences in ET-1 levels in TS patients compared to their matching age, gender and risk factor group between comparable groups, as seen in a clinical study [393].