Patients of an age of at least 18 years, an ejection fraction of 40% or less, NYHA class II, III, or IV. Patients were required to have a plasma level of N-terminal pro–B-type natriuretic peptide (NT-proBNP) of at least 600 pg per millilitre (or ≥400 pg per millilitre if they had been hospitalized for heart failure within the previous 12 months). Patients with atrial fibrillation or atrial flutter on baseline electrocardiography were required to have an NT-proBNP level of at least 900 pg per millilitre. The gene discussed is NPPB; the disease is atrial flutter.