Search the ACVIM database for a Cardiologist in your area.
This is the only institution in the United States that offers veterinary open heart surgery:
Here are some other notable veterinary teaching hospitals who may be able to help you:
None of these teaching hospitals are in your area? Here is a helpful website which lists all vet schools in the United States: http://veterinariancolleges.org/
If you know of a resource not listed, please submit to: firstname.lastname@example.org!