ECGs in medicals are used as a screening test and therefore come up with false positives (indicate something may be wrong but on closer looking all is OK) and false negatives (indicate all is well but have heart attack on the way out!)
Without knowing more details it is impossible to say whether you are going to be OK but as others have already said, you likely will be.
The idea behind medicals is that
1. you want to ensure that people can reach the standards which are deemed necessary to do the task of flying safely and
2. try to make sure that the people flying aircraft will remain fit to do so for the foreseeable (is duration of validity of your medical)
Ensuring the first bit is probably the easiest as you can just measure and see if people make the grade. The second one is a lot more difficult as it means that you have to start predicting things on the basis of some parameters, as you are dealing with individuals rather than large groups it makes for a not so easy process.
FD