When it comes to investigating heart issues we have a number of tests, some better than others. Although the chest x ray can suggest heart enlargement it is not as good as the echocardiogram. So the echocardiogram being normal means the chest x ray findings are not concerning. EKG patterns are not exact either, although the read form the machine suggests one thing, an entirely normal echocardiogram would suggest no previous damage has been done. Essentially in the echo you can directly see the walls of the heart and how they are functioning whereas in the other tests you cannot. So unless you have been told otherwise you can be reassured.