For more information please refer to Section 8.1 of the 2003 Guideline 22 . 2. Therapeutic drug monitoring of serum digoxin concentrations. For more information please refer to Section 8.4 of the 2003 Guideline 22 8.1 Monitoring using repeated biomarker measurement or imaging for management of chronic heart failure Clinicians treating patients with HF use a combination of symptoms (e.g degree of breathlessness) and examination findings (e.g. heart rate, blood pressure) to make decisions about treatment changes. Biomarkers are substances measurable in the blood stream which can be used to diagnose and monitor disease. Natriuretic peptides are released from the myocardium in response to fluid overload. The two main natriuretic peptides used in clinical practice are amino-terminal pro-B-type natriuretic peptide (NT-proBNP) and B-type natriuretic peptide (BNP). The measurement of natriuretic peptides is recommended for the diagnosis of HF but their role in the on-going management (i.e monitoring of heart failure) remains a topic of active research and there is uncertainty about the optimum diagnostic thresholds for natriuretic peptides. Troponin is released in response to myocardial injury and is important in the diagnosis of myocardial infarction but it s role in HF is unclear. Co-existing conditions such as chronic kidney disease (CKD) and atrial fibrillation (AF) can affect the level of biomarkers in the bloodstream and this may influence their utility in diagnosis and monitoring of heart failure. Similarly imaging techniques for HF such as cardiac MRI and echocardiography which can be used to assess the structure and functional status of the heart could be used for similar purposes. A number of evidence-based treatments for heart failure reduce hospital admissions and increase survival, particularly for patients with heart failure with reduced ejection fraction (HFREF). 