Fuente: WIPO "tomato" The present invention relates to peptides with 11-12 amino acids for use thereof as a medicine in cardiac diseases, especially ventricular arrhythmias in patients with cardiac hypertrophy, cardiac insufficiency (CI) and/or hereditary loss-of-function syndromes in the Navi.5 or Kir2.1 channels. The peptide with 11 amino acids and the synthetic analogues with 11-12 amino acids include a nuclear localisation signal, activate KCNJ2 transcription, prevent the decrease in the density of INa and IK1 caused by Cl, and significantly increase the density of INa and IK1 in cases of Cl. The invention also includes cDNA molecules that encode these peptides, the vectors and/or the cells containing them and pharmaceutical compositions containing same for use thereof in the prevention and/ or treatment of cardiac diseases.