To be clear, I'm not a doctor, but I am a pilot which means I know something about everything and my situation sounds similar to yours so here we go....
I'll be 60 later this year, but my entire life I've had abnormal EKGs... inverted T waves, I believe. I've also been a runner my entire life with heart rates in the 40s so I get Sinus Bradycardia messages as well. I actually found my EKG from when I was 17 years old for pre-entry to the Naval Academy and the same messages were there. And nobody from the Navy flight surgeons, AMEs, or the FAA ever seemed to care.... until suddenly they did. As you may know, the FAA requires a baseline EKG at 35 and then every year starting at 40. They flagged me at 45 and the letter came to me about 3 months after my last Class 1 medical with EKG. My point being that they already had multiple examples of my abnormal results and it was well after my last exam that they seemingly out of the blue had an issue with me. The letter that they send can be intimidating, basically saying that if you don't perform these certain procedures within 30 days, they will revoke your Medical.... and you will not be able to get it done in 30 days. Heck, you can't get into see any doctor in 30 days, much less a specialist. You can get an extension which I'll talk about later, but when making the appointments, don't be afraid to mention that your job is on the line. I found that I got expedited handling because of that. In the end, mine was pretty easy. Just a regular Stress test (not nuclear) and a cardiologist consult. In fact the cardiologist had me do a couple things over and above what the FAA was looking for like an echocardiogram just to make sure there were no underlying issues.
I have no idea what your specific issue is and hopefully you won't get flagged, but if you do (or for anyone else), here are a few tips that I'd pass along:
--- First, get yourself a good AME who gives a damn. At the time I got flagged I was going to a "fog the mirror" AME. He was a nice guy, but when I called him about my FAA letter, he wanted absolutely nothing to do with it. I immediately changed to a new Doc who really wants to keep me flying. His exams aren't really more onerous but he keeps good notes on me and has examples of my previous EKGs. He's been known to do a couple of EKGs and pick the best looking one to submit and essentially writes on them that it's a known issue with no changes from previous tests.
--- In the airline biz we have a phrase called "expand your team" and I highly recommend doing so. If you have access to AMAS (formerly ALPA's aeromedical branch now a standalone group) I recommend them. They are excellent at crossing T-s and Dotting I-s. They told me the exact phrasing to use for getting my extension and the exact order to put my paperwork into the envelope for my final submission. I also know there are entities at AOPA and a place called Leftseat that I can't vouch for. While AMAS was very helpful, I found them somewhat sterile and not particularly personable. I actually ended up calling my Regional FAA Flight Surgeon... now some might say that that's a risky step, but I had a great interaction with him (it didn't hurt that his brother in law was a fellow pilot at my 'Air Line'). He really put me at ease about the whole process. When I submitted my paperwork, AMAS told me it would likely take up to 6 months to get a reply from the FAA in OKC. Well, 2 weeks later I received a letter stating that my Medical privileges had been confirmed and it was signed by none other than my Regional Flight Surgeon who had been in OKC and hand carried packages from his area. You never know who you're gonna make friends with. ALPA was also helpful in that we get contractually reimbursed for any tests the FAA requires, so if you're in a similar situation, get everything done that will give you peace of mind. Lastly, while I didn't use him, our Air Line has a company Doc who may or may not be helpful in the process.
--- Be your own best advocate. If you aren't doing it already, ask for a copy of your EKG every time you have one and keep meticulous records. Make copies of everything you send to the FAA and bring it with you to every FAA medical exam. As I said, I have a long term AME that I like and who knows me, but every once in a while there are scheduling conflicts and I have to see someone else and that paperwork comes in handy. Lastly, my AME half jokingly recommends that both my wife and I keep a photo of my EKG on our phones in case I end up in the Emergency room for some unrelated issue because if they do a EKG, they're going to think I'm having a cardiac event!
I hope you never hear from the FAA, but if you do, it's not the end of the world. At the time I can remember being mid-career with kids going into college and being really worried. Now as I'm into 'area code' territory on my seniority list, I keep waiting for them to send another threatening letter so that maybe I can cruise my last couple years on disability, but they haven't sent me anything.....yet
