I've had issues with palpitations and tachycardia. my heart rate would get especially fast when lifting, from 120-160 bpm. i went to the cardiologist and was diagnosed with super ventricular tachycardia, more specifically, a sinus arrythmia. apparantly SVT is not uncommom, and sinus arrythmia is more common in younger individuals (i'm only 22). anyway, i went through ekg's, echocardiogram, wore a holter moniter for 30 days. in the end, the doc told me my heart was healthy, there was nothing they could permanently fix with an ablation procedure, and put me on a low dose beta-blocker to control the symptoms. it's helped quite a bit, and while i'm not thrilled about being on a beta-blocker all the time, i guess it's better than my heart feeling like it's going to beat right through my chest and run away.
i wouldn't necessarily think your situation is the same as mine, because mine was a gradual thing. the palpitations started a few years ago, and began to start happening more frequently and sometimes lasting awhile, so i went and did something about it.
some people get what's basically a "short-circuit" in their heart muscle in which some cells aren't conducting electrical signals properly, or are sending out their own. in these cases, an ablation can be done where they use an ultrasound on a small tube to "zap" the group of cells. i assume this kills those cells, but the procedure is common and supposedly very safe, so i guess it gets the job done. in any case, this wasn't an option for me since the electrophysiologist couldn't find any particular area that would be causing the problems. he felt it was more of a hypersensitivity to adrenergic stimulation. sucks, cause no more stimulant fat burners for me in the future.
talk to your doc about wearing a holter moniter for awhile. 1 day is not enough, although that's all most docs make you wear one for. like i said my doc had me wear it for 30 days. while it's definitely an inconvenience, it gives your doc alot more to go by when trying to make a diagnosis. an echo might not be a bad idea either.