Usually an enlarged heart is not normal. However, measuring the heart is very subjective and can be different depending on the individual or the machine measuring it. Also, the size of your heart should also be compared to the size of your body so a heart that looks mildly enlarged in a 6'4" man may actually be normal for his size.
If you do have an enlarged heart you can still live for a long, long time depending on the scenario and appropriate medications.
Hope this helps.