Was it the same Doctor? Every Doctor will take the results as different values. For example, some cardiologists will say everything is normal if there is a slightly leaking valve, whilst others will raise it. It could be due to a number of factors why the new results are normal. The last test you may have had loose leads or even an infection going on. Now the leads could be attached properly and you are clean from infection. Another issue is that you may have opened some collateral vessels which are natural bypasses in the heart to go around blockages. If I had to guess, I would say that you may have had some leads slightly in the wrong place last time, or loose. Either that or the cardiologist isn't concerned by the results at all.
Are you still getting the chest pains?