Welcome @harp23, I had not heard of Nattokinase but I just started on Eliquis (5mg) twice a day after a trip to the ER and an overnight in the hospital for a blood clot in my leg and then one in my lungs. I don't have AFIB but do have hypertension so also take high blood pressure meds. I have to go back in January for an ultrasound to look at the clots and determine if I need to be on Eliquis a few months longer or if it is a lifetime thing. After doing a quick search and finding the following article, I think I might discuss Nattokinase with my vascular medicine care team to see if it might be an option.

"Nattokinase dissolves blood clots by directly hydrolyzing fibrin and plasmin substrate. It converts endogenous prourokinase to urokinase (uPA). It also degrades plasminogen activator inhibitor (PAI-1) and increases the level of tissue plasminogen activator (t-PA)."
--- Nattokinase: An Oral Antithrombotic Agent for the Prevention of Cardiovascular Disease:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5372539/.
I would not take Nattokinase without discussing it with my care team especially if you take any other blood thinners or medications. Here are a few more research articles:

"Nattokinase has not been approved by the FDA, and contrary to claims on the internet, it should not take the place of an anticoagulant."
--- Can I replace prescribed anticoagulants with Nattokinase?: https://www.stoptheclot.org/faq/can-i-replace-prescribed-anticoagulants-with-nattokinase/

--- Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6043915/.

Have you discussed it with your doctor?