That Mean Girl

Especially after I eat or drink anything containing a lot of caffeine, I get very very tired and slightly dizzy, my muscles all feel drained and I feel the need to sleep for a few minutes. Occasionally, the tiredness is accompanied by a rapid, hard heartbeat that can last anywhere from fifteen seconds to two minutes, after which I basically pass out. This is not always preceded by a rapid heartbeat; however, it is always after I've consumed something with a lot of sugar or caffeine (or both). The attacks are more frequent if I haven't had sufficient sleep for a few days. I've had three EKGs, including a 48 hour Holter monitor, on which nothing has shown up out of the ordinary. My doctor tentatively diagnosed me with SVT and recommended a beta blocker as well as showing me some tricks to regulate my heartbeat (gagging, coughing, etc). I disagree with the need for medication if the doctor isn't positive it's SVT and she admits that it's hard to diagnose.

So, does anyone know whether caffeine can cause SVT? It seems more like a symptom than the cause of whatever is wrong, since it doesn't noticeably happen every time. I don't want to throw medication at a symptom when I could be attacking the actual problem.

Note: I originally went in to be tested for diabetes. The test came back negative.