@eddiereen Since your husband is a veteran and being treated at the VA, may I suggest that you contact the Veterans' Affairs Department in your state? If you are in Wisconsin, begin at https://dva.wi.gov/Pages/Home.aspx or call 800-947-8387.
They can direct you to someone who will help you sort out what your rights are. Treatment outside the VA is possible, and even common. Also, is the Cardiologist in Marshfield able to give you a referral to Mayo? I am not sure of the procedure when you have VA benefits.
Sue