Atrial Fibrilation caused by thyrotoxicosis?

[ando35]

My brother has had two incidents of AFIB in the last month. He was chemically and electrically cardioverted to stop the arrythmia.

His doc is saying it is caused by thyrotoxicosis.

His Ft3 was 3.8 ref 2.0-3.5
his Ft4 was 1.1 ref 0.9-1.7

Does anyone have any knowledge about this?

Not sure what his tsh was. He never had any diagnosis of hyperthyroid before.

[gimel]

I would also consider the fact that hypothyroidism can also cause cardiac issues.  Even though the Free T3 was high, the Free T4 was low in the range, which does not fit with the high Free T3.  That made me wonder if there was a possibility of T3 pooling in the blood, causing the high Free T3. With pooling the T3 is not getting into the cells of the body and will result in hypothyroidism.   Here is some info on pooling.

"T3 Pooling

What is Thyroid pooling? This is when the thyroid hormone T-3 collects or pools in the blood and does not get into the cells.

How does T3 Pool? The cause of T-3 pooling can be any one of the following or a combination of the following:

    High cortisol
    Low cortisol
    High iron
    Low iron
    Medications
        beta blockers
        Amiodarone
        Iodinated contrast media
        Lithium"

So I think it would be a good idea to test the TSH, re-test the FT4 and FT3, and also test ferritin and cortisol.  Note that the best way to test for cortisol is the 4 panel diurnal saliva cortisol tests.  Doctors usually only want to run a serum cortisol test, but it is not as revealing as the saliva cortisol tests.  

[yankeeRN]

Hyperthyroidism can cause AFIB --it's not the only cause but certainly the thyroid levels are always checked when a patient has a new onset AFIB. His Ft3 is elevated --his Ft4 is within the range and yes it would be nice to see what the tsh was with those results.  I would hope he is being worked up further for his thyroid to see what specifically is going on.  Good luck.