Can someone please give me any advice as how to find out if my son had myocarditis?

I am wondering if anyone can give me any advice. My son died suddenly last year and I am trying to find out why as the inquest came back as death unknown.
I have had a second opinion and still no answer.
After researching on the internet, it seems likely that he might have died from myocarditis.  He rang me that he had been diagnosed with tonsilitus but felt this was a misdiagnosis. He was hot with cramping of his leg muscles , and was really short of breath. Also vomitting. In hospital , he was given massive doses of antibiotics and he deteriorated straight away and died. His tissues are still at the hospital and would appreciate any advice as to what type of medical expert I should contact and whether it can be detected through tissue samples. I just need to know what happened to him as I feel I cant rest till I find out. Thank you for any advice

[Cleveland Clinic]

First let me express my deepest condolences. If an autopsy was performed, then the size and microscopic appearance of the heart musculature should give you the answer to your question. If his heart was not enlarged and/or inflamed then most likely it was not due to myocarditis. Perhaps he died from an overwhelming infection, such as a pneumonia? This could be confirmed from pathology from the slides of the lungs and tissue culture. If there continues to be questions surrounding his death, you may request to speak to the coronoer's office who is required to perform an autopsy in most states in cases of sudden deaths such as his.