Biomarkers that are surrogates for cardiac pathophysiology may help us understand the "state of the heart" in heart failure and may be indications for certain treatments. A good biomarker will also be able to be monitored and a change in the level will reflect a change in the condition. I will speak of three biomarkers that do exactly this (natriuretic peptides, high sensitivity troponins and sST2). Natriuretic peptides (NPs) (BNP and NTproBNP) are guideline standards to confirm the diagnosis of heart failure. They are good for monitoring volume as we diurese the patient. Their weaknesses include wide variability in levels in a given patient as well as elevations not secondary to an increase in left sided filling pressures. Additionally, their value is questionable in patients receiving Entresto (a drug that inhibits breakdown of NPs). High sensitivity troponin in the setting of acute heart failure (and maybe chronic) represents subendocardial necrosis and has a bad prognosis. It is possible that drugs like nitrates will be used in heart failure treatment more commonly when levels of high sensitivity troponin are high. Finally, sST2 is a marker of fibrosis and is elevated in virtually all patients with heart failure. In the acute setting, it defines a "sicker" patient who needs advanced treatment to avoid re-hospitalization. In the chronic setting, titrating medication to a sST2 level below 35 ng/ml appears to mitigate risk, even in the setting of a continued high NP level. Data with Entresto suggest sST2 levels are going to be useful in both selection of patients for Entresto as well as monitoring treatment and maybe regulating the dose.