An enlarged heart may be caused by a thickening of the heart muscle because of increased workload. (This increased workload can be due to heart valve disease or high blood pressure, for example.) This is called hypertrophy (hi-PER'tro-fe), which refers to enlargement of an organ or tissue due to an increase in cell size.

Left ventricular hypertrophy (LVH) is the medical term for enlargement of the left ventricle. (The left ventricle is the heart's main pumping chamber.) Hypertrophy also occurs in hypertrophic cardiomyopathy (hi"per-TRO'fik kar"de-o-mi-OP'ah-the). Enlarged heart may also be a dilation (expansion) of the heart due to damage that weakens the heart muscle. Examples include heart attack, congestive heart failure and dilated cardiomyopathy. (Cardiomyopathy is a serious disease in which the heart muscle becomes inflamed and doesn't work as well as it should. For more information, see the Cardiomyopathy entry in this guide.)