After crossy country practice today something wierd happened. We had just finished sprinting and when we slowed to a walk i noticed that with each beat my heart seems like it vibrates/buzzes. As soon as i walk for a few seconds or minutes, the buzzing is gone. Anybody have this happen or know what the signs are? Later in the day i had some should soreness and slight chest pain. Whats going on? I passed a stress test with flying colors 2 weeks ago and the same with an EKG and ECG in May 2006. Should i be worried? Any advice greatly appreciated.

Oh yeah, im a 16yo male (SVT at Birth but no problems since), 140pds, and have been on varsity XC for the past 3 years with no problems. Wish i knew what was going on. I dont want to damage my heart.