Immigration Canada can deny people based on a clause called "excessive demand" where they decide that this person will be a burden on Canada's health care and/or social services. If they feel that your medication is too expensive or that you may need another transplant in the future, they could deny based on that. You could try to appeal their decision showing that you have funds or insurance to cover your potential problems yourself.
There is one exception to excessive demand and that is if you marry a PR or a Canadian and get sponsored as a spouse. In that case, you would not be subject to that clause.
