Heart failure is a common clinical syndrome caused by different cardiovascular diseases. The prognosis is poor once the stage of congestive failure is reached. Several non-invasive and invasive techniques, described in this article, are used to objectively diagnose systolic or diastolic failure at its early stage. These investigations are needed to assess, not only the cardiac dysfunction, but also the underlying cause of the failure. Early and effective treatment should prevent or delay the occurrence of the signs of congestive failure and thus improve the prognosis.