Up to 20% of patients given rhIL11 (50 μg/kg) develop atrial arrhythmias, a high proportion of individuals develop heart failure, and rare cases of ventricular arrhythmias and sudden death are reported.11,12 Furthermore, serum natriuretic peptide levels become acutely and transiently elevated in patients receiving IL11 therapy, with B-natriuretic peptide levels sometimes exceeding those diagnostic of heart failure. This evidence concerns the gene NPPB and heart failure.