The ABC of heart failure investigation outlines the essential steps in diagnosing and managing heart failure. Clinical assessment is crucial before detailed investigations, though specific features may be absent. Initial investigations include chest radiography, 12-lead ECG, echocardiography, haematology tests, serum biochemistry, and cardiac enzymes. Chest X-rays can show cardiac enlargement, pulmonary congestion, and other signs, but they may not reliably distinguish between cardiac and non-cardiac causes of dyspnoea. Echocardiography is the most useful non-invasive test for assessing left ventricular function, identifying systolic and diastolic dysfunction, valvar disease, and other abnormalities. It helps guide treatment decisions, such as the use of ACE inhibitors. Electrocardiography is useful in identifying left ventricular systolic dysfunction, with high sensitivity and negative predictive value. However, it may not always be normal in heart failure patients. Haematology and biochemistry tests help exclude anaemia, metabolic disorders, and assess renal function, electrolytes, and liver function. Radionuclide imaging and cardiac catheterisation may be used in complex cases. Pulmonary function tests help exclude respiratory causes of breathlessness. Coronary angiography is essential for assessing coronary artery disease. Cardiopulmonary exercise testing assesses exercise tolerance and helps in evaluating prognosis. The value of electrocardiography in identifying left ventricular systolic dysfunction is high, with a high negative predictive value. Echocardiography is vital for assessing heart failure and guiding management. The importance of these investigations varies, with some being more critical than others. The ABC of heart failure is a comprehensive guide for healthcare professionals in the diagnosis and management of heart failure.The ABC of heart failure investigation outlines the essential steps in diagnosing and managing heart failure. Clinical assessment is crucial before detailed investigations, though specific features may be absent. Initial investigations include chest radiography, 12-lead ECG, echocardiography, haematology tests, serum biochemistry, and cardiac enzymes. Chest X-rays can show cardiac enlargement, pulmonary congestion, and other signs, but they may not reliably distinguish between cardiac and non-cardiac causes of dyspnoea. Echocardiography is the most useful non-invasive test for assessing left ventricular function, identifying systolic and diastolic dysfunction, valvar disease, and other abnormalities. It helps guide treatment decisions, such as the use of ACE inhibitors. Electrocardiography is useful in identifying left ventricular systolic dysfunction, with high sensitivity and negative predictive value. However, it may not always be normal in heart failure patients. Haematology and biochemistry tests help exclude anaemia, metabolic disorders, and assess renal function, electrolytes, and liver function. Radionuclide imaging and cardiac catheterisation may be used in complex cases. Pulmonary function tests help exclude respiratory causes of breathlessness. Coronary angiography is essential for assessing coronary artery disease. Cardiopulmonary exercise testing assesses exercise tolerance and helps in evaluating prognosis. The value of electrocardiography in identifying left ventricular systolic dysfunction is high, with a high negative predictive value. Echocardiography is vital for assessing heart failure and guiding management. The importance of these investigations varies, with some being more critical than others. The ABC of heart failure is a comprehensive guide for healthcare professionals in the diagnosis and management of heart failure.