Unequivocal results of high plasma ET-1 levels and increased mortality in patients with CHF may be due to difficulties in the precise measurements of the rather unstable ET-1 in circulating blood (resulting from its short plasma half-life [14], its intermediate clearance by receptor binding in the pulmonary vascular bed [15], and its degradation by neutral endopeptidases [16], [17]. The gene discussed is EDN1; the disease is congestive heart failure.