(copy from same question in other thread)
The FDA's approach is different to Europe. In the USA, standards are not part of the law, rather the FDA simply says they promise to process your 510(k) or PMA quickly if you use standards.
Once the 510(k)/PMA is approved (clearance for sale), that's it. The device is in principle allowed to be marketed forever, provided you don't make any design changes.
If you make a design change, the FDA gets a bit warm and fuzzy and not really clear (highlighting the lack of legal backbone behind the use of standards).
See
FDA Guide, Items 9 and 11.