A pharmaceutical composition can be provide for treating or preventing heart failure. Additionally, siRNA and a vector expressing said siRNA can be provided that can be used in the pharmaceutical composition for treating or preventing heart failure. For example, a pharmaceutical composition can be provided for treating or preventing heart failure that contains a DNA sequence encoding RNA containing a sense strand sequence of consecutive 18 to 29 nucleotides from angiopoietin-like protein 2 (ANGPTL2) mRNA or the alternative splicing type RNA thereof and an antisense strand sequence complementary to the sense strand sequence under control of a promoter, and a pharmaceutically acceptable carrier.