Cardiomegaly refers to an abnormal enlargement of the heart, typically detected via imaging studies such as chest X-ray or echocardiogram. It is clinically significant as it can indicate underlying conditions like hypertension, heart valve disease, or cardiomyopathy, potentially leading to heart failure if untreated. A key association is with dilated cardiomyopathy, where the heart's ability to pump blood is compromised, increasing morbidity and mortality risk.