MI-induced HF resulted in a 20% decrease in left ventricular (LV) ejection fraction (EF) (Figure 1B), as well as an increase in heart weight, LV inner diameter, and a four-fold increase in atrial natriuretic peptide (ANP, encoded by the NPPA gene) expression (Figure 1C–E). The gene discussed is NPPA; the disease is hydrops fetalis.