W.P.W. Syndrome, it is where there is extra nodes in your heart conducting your heartbeat and actions like running, laughing sometimes, bending down and coming up fast can cause it. i only say this because you are describing exactly what happened to me when i was diagnosed with it when i was 14 and running in 8th grade. it would happen for 15-45 minutes and my heart rate would be around 240bpm. we went the ER the next time it happened (because they can only catch it on an EKG while it is happening) i had a procedure called a Catheter Ablation a month later, then again 6 months later. it is not an open heart procedure but one where they make a tiny incision in your main artery in your leg/groin and with a catheter (mechanical wire type thing) the doctor can move around your heart and zap away the extra nodes. i am 20 now, it only came back 5 years later (this past july) and i had another catheter ablation and i am all better now. your first action is to either wait till it happens (but be careful because if it gets close to 300bpm you can go into cardiac arrest) and go to the ER so they can take an EKG and get proof then refer you to a cardiologist, or just go to a cardiologist and they may fit you with a heart monitor that you would wear all day (little things stuck to your chest) and you would record the events and call a number and they basically take an EKG reading that a cardiologist can then determine from. it sounds like you only have a very slight affliction compared to some, even mine, so they may put you on the monitor and it would show it not WPW but SVT or a rapid beat. email me if you have any more questions i would be more than happy to help.