Breast cancer is the most common cancer in the United Kingdom (UK), but improvements in treatment mean 3 in 4 people survive for more than 10 years. Many people receive treatments called human epidermal growth factor receptor 2 (HER2) targeted therapies for their breast cancer, however these can affect heart function. This 'cardiotoxicity' is generally temporary and mild, but patients receive drugs to help their heart recover. Currently it is not known how long patients should receive these treatments. Patients with other types of heart failure are treated lifelong, but this may not be necessary here as the damaging cancer drugs have stopped. Taking drugs for many years can have an impact on people's quality of life, particularly for young patients. It is therefore important to understand the best treatment length. The investigators will study people whose heart function has recovered after HER2 therapy heart problems and are not at high risk for heart disease. The investigators will carefully stop their heart drugs whilst monitoring them closely with special heart scans and blood tests to detect problems early. The investigators will also study how patients are currently treated using national data. The results of this study will help doctors better guide breast cancer survivors about treatment of heart damage from HER2 cancer therapies.