I should also have said that if you haven't seen your endo since being diagnosed with S2DHF, you might want to. T3 meds are often contraindicated with heart problems. He might want to re-evaluate at this point.
The reference range for FT4 is usually in the vicinity of 0.8-1.8, so I'll base my comments on that, but you should verify that this is close to your lab's range.
Your FT4 is a little on the high side. It's in the upper quarter of the range.
Unfortunately, we don't know your FT3. I just read your profile and see that you take Cytomel as well as Synthroid. If your cardio really wants to monitor your thyroid hormones, he should be testing FT3. FT3 levels are much more important than FT4 when it comes to cardio issues. Monitoring FT3 is especially important when you are taking T3 meds (Cytomel).
As you note, your TSH is a little low. However, do remember that TSH causes no symptoms. TSH is nothing but a messenger from your pituitary to your thyroid to tell it to produce hormones. We often see TSH suppressed when people are taking T3 meds.
All that being said, how do you feel from a thyroid point of view? Are you having any hyper symptoms? How do these labs compare to previous labs? Has your FT4 been consistently at the higher end of normal?
I suspect that your cardio is reacting mostly to your TSH level. Many doctors are unaware of all the factors that can affect TSH and tend to panic when TSH goes out of range, especially when it does so on the lower side. They equate low TSH with hyper, but that's not necessarily so.
Please post your doses of Synthroid and Cytomel as well. Has your current endo been managing your thyroid right along? From your profile, I take it that you have never felt truly well since being on thyroid hormone replacement???
I was recently diagnosed with Stage 2 Diastolic Heart Failure. The cardiologist only checked a TSH and a FT4. He has said that my thyroid never being properly managed could have caused the heart failure, so he is keeping an eye on its function. The lab range shown at the lab where these were checked showed the FT4 to fall within range, but of course the TSH is too low. He seemed to be quite concerned about these numbers. Do they seem concerning to anyone else?
What's the range on your FT4? Did he test FT3?
Why do you see a cardiologist?