You will need an echocardiogram. It uses sound waves to create detailed pictures of all the chambers of the heart and the heart valves. The pictures also show how well each part of the heart is functioning and whether blood flow is always moving in the right direction.
Your heart might not even be enlarged. And if it is slightly bigger than expected, and the echocardiogram is otherwise completely normal, you can be reassured that this is normal for you.
People with high blood pressure who don't keep it under control can develop a large left ventricle. The left ventricle is the main pumping chamber in the heart. It needs to push blood out to the rest of the body.
Make sure you ask about the size of your left ventricle and whether the thickness of its wall is normal. A thick left ventricle wall, called left ventricular hypertrophy, indicates that you need to get your blood pressure to even lower levels.