For example, exacerbated activation ofthe sympathetic nervous system developed during heart failure associated with mitralvalve disease can be monitored by measuring the plasma concentration ofnorepinephrine (NE), which is associated with severe symptoms and a higher risk ofdeath.3,4 The importance of the amino-terminal pro-B-typenatriuretic peptide (NT-proBNP), an inactive amino-terminal fragment of theprohormone brain natriuretic peptide, has been recognized in recent years. The gene discussed is NPPB; the disease is mitral valve disorder.