Hi Seishin,

I am not diagnosed yet, but have some form of weakness. I also had my heart rate spiking to about the same range as yours with very minimal effort. It took several years to get the help I needed; I learned that you need to be a squeaky wheel with your doctors until you get what you need. If they do a test and it shows nothing, don't just say "oh." Say, "I'm still having trouble, what are we going to do about it?"

I was ultimately diagnosed with dysautonomia. In my case, the high heart rate was not dangerous at all, just extremely uncomfortable. It is also now controlled with medications. The cardiologist did not arrive at this diagnosis until he had ruled out any problems with my heart, including a 24-hour Holter monitor, an echocardiogram (the ultrasound, like Annie described) a CT scan, a stress test with imaging, and ultimately a 30-day Holter monitor.

I tell you about myself to give you some comfort that it might be nothing serious, but you do need to be checked out thoroughly. Also, you could check out dysautonomia (especially "Inappropriate Sinus Tachycardia") to see if it sounds familiar.

Tatia

P.S.- My in-laws have a genetic thing which causes their heart rate to go up as high as 400 to 600 BPM.