Circulating miRNA‑21 is a promising biomarker for heart failure.

microRNA 21 (miRNA‑21) promotes the development of cardiac fibrosis, hypertrophy and heart failure. However, whether it can be used as a biomarker for the diagnosis and prognosis of heart failure remains unclear. The current study assessed circulating miRNA‑21 as a viable indicator for diagnosis and prognosis of heart failure. The levels of miRNA‑21 and brain natriuretic peptide were measured in serum obtained from the peripheral vein (miRNA‑21‑PV) and coronary sinus (miRNA‑21‑CS) of 80 patients with heart failure and 40 control individuals via reverse transcription‑quantitative polymerase chain reaction and ELISA, respectively. The correlations between circulating miRNA‑21 and diagnosis, severity, prognosis and re‑hospitalization rate of heart failure were evaluated using statistical analysis. Serum miRNA‑21‑PV and miRNA‑21‑CS levels of patients with heart failure were significantly higher than that of control subjects, and were also correlated with ejection fraction and brain natriuretic peptide. Both were determined to have high levels of sensitivity and specificity for diagnosing heart failure. Follow‑up of the patients with heart failure indicated that miRNA‑21‑PV and miRNA‑21‑CS were correlated with prognosis, and miRNA‑21‑CS was efficient in predicting re‑hospitalization for heart failure. Circulating miRNA‑21 has potential to be a biomarker of heart failure.