Finding new ways to diagnose and treat Dilated Cardiomyopathy (DCM) could improve the health and well-being of patients with this condition. The main aim of this research study is to help develop better ways of diagnosing and treating patients with DCM. The information that is collected may help develop tailored treatments for patients with this disease in the future. This research study will recruit patients with DCM from a number of centres across England and follow their health over a period of years. Patients will give some blood samples for a type of genetic test called whole genome sequencing (WGS) to look for genetic changes. Patients will also have a magnetic resonance imaging (MRI) scan of their heart to look for any changes in the heart such as scarring, and check their heart function. The aim of this study is to discover if using WGS and MRI can improve the diagnosis of DCM. Another aim of the study is to look at how genetic changes and scarring in the heart may affect the progress of the disease. Studying patients with DCM may also help the investigators learn more about diagnosing and treating other diseases of the heart. The second aim of this study is to see whether using WGS and MRI scanning can also be useful in other types of heart diseases which might be affected by genetic changes or scarring in the heart.