What Causes Severe Foot Pain In A Heart Patient?

My husband had a stroke last November. At that time we also discovered he had a fib. After being stable for a few months, it shocked it back into rythym. One of the medications they prescribed was Zarelto. For many years has had chronic severe foot pain that over 5 specialists have not been able to diagnose . Prior to the stroke He had been taking Aleve daily and was pain free. Of course no one wants him to take Aleve anymore. The pain is not from arthritis or PAD, or anything a orthopedic surgeon could see. After living 24/7 pain were walking becomes almost impossible, tests, tests and no solution. in desperation he took one Aleve and was pain free again. We realize this is not recommended, however with no other answers we would like to know what are some warning signs that we should watch for? OR another solution?