The relationship you have with your cardiologist will make a difference. My suggestion is you write a sample letter using the proper terminology such as "in my opinion herbicide exposure was "more likely than not" the cause of Mr. Gee's Ischemic Heart Disease. I have reviewed Mr. Gee's military records and see he was stationed in Thailand where many articles support the use of various herbicides at Thailand bases.
Provide him/her a brief synopsis of your military history (entered service on such date- sent to basic training, on such date sent to technical school, on such date sent to duty station...etc), you get the picture. Make this short and sweet. Tell him/her many internet and news articles about herbicide use in Thailand, explain Agent Orange is a herbicide. Ask him/her to put your sample on their letterhead and sign with their physicians number. By giving you military history there are no untruths any where in your letter. just my thoughts....good luck. The key is to keep everything short and concise. LouB.