I'm 25 years old and have experienced a recurring, random, and infrequent heart problem since I was 11 or 12. Occasionally during sustained cardio exercise, my heart will jump from an 'at work' heart rate of ~160 bpm to a heart rate of about 240 - 260 bpm. This jump is accompanied by a sudden dizziness.
My limbs will start to feel heavy and simple movements require more effort, and I have to stop whatever exercise I may be doing(though it's more common for this to happen when I'm at rest between sets.) With some luck, I can usually lie down and elevate my feet immediately after the 'jump' and my heart may return to a normal pace, but this isn't always the case and the condition may sometimes last for up to an hour.
I've taken many EKG tests, stress tests, and heart monitor tests in the past few years, but, unfortunately, during these tests I could never get the event to "trigger" even when I've tried to do so intentionally. So no one could diagnose the event.
Like I said, it's random and infrequent, but when it happens.. it's debilitating.
yeah, I know I wrote a mouth-full.. but any help here would be.. helpful..