Sir,—It has been well documented that neurohormonal mediators, such as the renin–angiotensin system,1 endothelin,2 and brain natriuretic peptide (BNP),3 are severely activated in patients with congestive heart failure, and that the circulating concentrations of these mediators are good predictors of the severity of congestive heart failure and the prognosis. It has also been demonstrated that both angiotensin II and endothelin-1, like BNP, are locally expressed in cardiac tissue.4-6 It is not clear, however, whether the increase in plasma concentrations of angiotensin II and endothelin-1 is caused by increased expression and spillover from cardiac tissue in patients with …