Clonidine and Losartan work wonders for me. It is my theory that in CFS and FM there is enhanced norepinephrine stress. Those two drugs work great for that and probably have the best chance of stopping the arrhythmias. I know because I was airlifted to a university hospital with a 200/140 blood pressure and a 140 pulse that would not go down for days until I demanded these two drugs after I was released. My EKG showed I was having a heart attack with a tombstone readout (which most people do not survive). There was no heart damage and therefore apparently no heart attack. This gives you an idea of how crazed the sympathetic nervous system can get in CFS. If I save your life, thank me later.
As for the stomach problems and the heart problems...all are symptoms of an overactive sympathetic nervous system. This can be genetic, from active infection, and or from hormonal problems.
My cardiologists were useless - they sent me home on a calcium channel blocker with dangerously elevated blood pressure. I have no faith in doctors, partly because they prescribe drugs and really do not give a crap about follow up or underlying mechanisms to disease.