Echogram will disclose size of heart better than X-ray and will also any valvular irregularity and the GROSSEST picture of arterial clogging. Also any congenital problems.
Next in the hierarchy is stress test and scan of nuclear markers to pinpoint any coronary areas that are being shortchanged of nutrients causing angina (pain on exertion/shortness of breath.) If the last (which your really SHOULD have done with your symptoms...it will make the echogram unnecessary) shows evidence of arterial blockage, then the gold standard test is the cathetered angiogram. During that procedure, if a blockage is discovered it can be opened (angioplastied) and stented.
EVENTUALLY, all these tests will be rolled into one wonderful super-sensitive MRI that can do everything non-invasively and eliminate the rinky dink stepwise procedure. But then the medical community has never had a test that it abandoned lightly (witness the continued presence of the 100 year old mercury shygmomanometer...and LEECHES are even making a comback...and shock therapy, etc. etc.
Anyone see trepanning around the corner?