Cardiomegaly means: The enlargement of the heart. The term cardiomegaly, which is descriptive of an abnormally enlarged heart, isn’t a diagnosis. A variety of conditions can cause cardiomegaly, including heart valve diseases, heart muscle disease, heart rhythm problems, high blood pressure and arrhythmias. Long-term anemia, thyroid disease and other diseases can sometimes lead to cardiomegaly. The underlying cause will determine the treatment and outlook. Sometimes referred to also as an enlarged heart.
(in Medical Dictionary)

What else does Cardiomegaly mean?

The expansion of the heart.
(in Merlin Dictionary)