Have you been tested for a pheochromacytoma? I had junctional tachycardia from the age of 13 (officially diagnosed in my 20's) and it got worse as I got older - add on atrial fibrillation.
When I was trying to get pregnant, I went to a fertility specialist and found out I had PCOS. When I went in for surgery, my blood pressure shot up through the roof - we're talking 200/180 and the surgery was put on hold. Cardiologist came in, put me on some meds and surgery was later rescheduled.
Fast forward to when I got pregnant at the age of 38, I was obviously teamed up with a high risk obgyn. I had to get off all heart meds to keep it safe for my baby and I just tried to take things easy. As my pregnancy progressed, my blood pressure started to rise (p.s., I'm a healthy woman, not overweight - 5'8" 140 lbs.). The afternoons were the worst for me and I would often have to lay down at the office to get my heart to go back to normal. One day, I had a check-up in the afternoon and my heart started to go whackadoo while being monitored. I was admitted to the hospital and for 3 days they ran tests on me. Turned out my heart condition that I had for most of my life was actually a tumor on my adrenal gland - pheochromacytoma. Apparently, it's fairly rare. I had been tested once before but the results came back inconclusive and since it was so rare, they just assume at that point that it's negative.
I had laproscopic surgery to remove the tumor and my life has changed dramatically! While I still ocassionally have rapid heart rate, it is nothing like it was before. Prior, I was unable to even get up in the morning and get ready without having to lay back down. Changed my life! And, it wasn't a cardiologist who diagnosed me but my obgyn. Amazing right? Bottom line, if you think you have something, go to a specialist in that field to get tested. Do as much research into every possible cause and never give up till they find the answer. I had all but given up that I just had a bad heart.
Good luck!
S.