NPPB and AL amyloidosis: Involvement of the heart is the commonest cause of death in AL amyloidosis and is a major determinant of prognosis; without cardiac involvement, patients with AL amyloidosis have a median survival of around 4 years,26 but the prognosis among affected patients with markedly elevated BNP and cardiac troponin (Mayo stage III disease)27 is on the order of 8 months.