There are still a variety of interest-free intro offers within the US...not sure if they exist elsewhere. Lengths tend to vary...the last one I had come in was a twelve-month no-interest term, after which any remaining balance would be assessed at the go-to rate (most of my cards are under 10% with a few still sitting under 5%).
Most medical facilities DO accept plastic, but you would need to discuss what cards they accepted. Someone else mentioned Care Credit (and I think Chase also offers a health account), but APR's can be higher on those. If you got an offer with an intro 0% rate (Care USED to do some of those for persons with good credit), the balance could then be rolled to another card when the promo term was about to expire.
Yes, card arbitrage is something I have experience with, albeit for other reasons than medical expenses