Inflammation in the myocardium or myocarditis is a disease with heterogeneous aetiology, frequently caused by an infectious pathogen, toxins, drugs or by an autoimmune disorder. Its clinical variability and its nonspecific symptoms make the diagnosis of myocarditis a process that is not always easy. There is an urgent need for accurate, fast point-of-care tests that simultaneously provide diagnostic and prognostic information about a patient entering the hospital with symptoms of acute heart failure. CNIC researchers have identified the role of an specific miRNA in cardiomyopathies processes and have studied the differential expression in blood plasma of patients compared with healthy subjects. These miRNAs can be used as biomarker to improve the diagnosis of acute myocarditis.