Heart failure is hemodynamically characterized as congestion and/or end-organ hypoperfusion, and is associated with increased morbidity and mortality. Underlying pathophysiology, such as neuro-hormonal activation, exacerbates heart failure and leads to functional deterioration of other organs. We have been conducting clinical research to study the pathophysiology of heart failure and discover prognostic factors. In this review article, we report the results and implications of our clinical research on heart failure.