It means there is an abnormality that could possibly represent a past heart attack. A cardiologist will run more specific tests to find out for sure the reason, if any, for your abnormal testing. Sometimes there are also false positives, so wait until you get the word on the situation from the cardiologist.
Both my husband and I had EKG's which showed a "previous heart attack" which we never had, thanks to the test results of several tests which proved NO heart attacks, ever. They can take their computerized EKG's and stick them where the sun don't shine. People don't need to get/hear "false positives" with something as serious as the heart.
The Cardiologist will run tests, and will explain to you exactly what is or is not wrong with your heart.
Don't do like I did and go to pieces with worry before you even see the Cardiologist.