Enlarged heart. Coloured chest X-ray of a patient with gross (severe) enlargement of the heart (red), known as cardiomegaly. Cardiomegaly can be symptomless and may only be detected on a chest X- ray. There are a variety of disorders that can cause cardiomegaly, including as a response to excessive strain, such as obesity or a weakening of the heart muscle (cardiomyopathy). The gradual loss of heart function (heart failure) causes breathlessness and exhaustion, even when at rest. Various drugs help in managing the symptoms, with transplantation as a last resort.