Do I have an arrhythmia, nervous system problem? Six weeks ago I had a tachy brought on by lack of sleep (50 hrs) and taking in tons of caffeine (1600mg in 12 hrs).  I have been to tons of doctors, cardiologists, oncologists and have been through tons of tests.  The only thing they have found so far is a slight mitral valve leak.  This could not be causing my heart rate to jump from 60-65 at rest to 100-110 as soon as I stand up.  My heart races with minimal physical exertion and all they found with all these tests was a slight valve leak?  I bought a $50 heart rate monitor and found the 40 to 50 beat jump on my own.  I have told every doctor I have seen about this before testing it on my own and none of them has been concerned about it.  They are telling me that I am in perfect health and do not have an arrhythmia.  Could I have messed up my nervous system?  When my heart started beating really fast I thought I was having a heart attack and panicked.  I have read that going through trauma like that can cause this.  Thoughts?

Summarized question: What could cause a sudden heart rate increase when standing?