I had a treadmill stress test this morning. I felt great. I never even started breathing hard (I run and walk several times a week). When the test was complete, my doctor said it was a false positive result, based on the fact that I was felt perfectly fine while I was walking/running but my EKG was "not normal". Also he said that as soon as I stopped the test, my EKG immediately returned to normal. So he wants me back next week for an echo stress test (echocardiogram before and after the treadmill stress test).

Has this happened to anyone else before? What were your experiences? How common is this (I've read that from 10% to 40% of treadmill stress tests produce false positive results)?

A false positive result is better than a false negative result. At least the doctor will keep an eye and investigate further in case it is not a fault.

Mine one turn out could be artefacted. My doctor over confident and claim that I'm a female. End up I have a heart attack and causing a permanent damaged in my lower left ventricle. Now end up I have a severe hypokenises and my heart doesn't want to beat anymore..... :( My cardio still think the echo is an error. He didn't want to accept his over confident, he afraid I'll sue him!