Autopsy and medical examiners report

My ex husband died at work of a sudden heart attack at the age of 45. Never was sick and no known heart issues. The hospital the ambulance took him to sys that no autopsy was done and no medical examiners report all they have is a ambulance report and an emergency room paper. They called his father in Virginia for permission to do autopsy .said it's the law then doesn't do one I have his 2 children and don't even know the cause or if it was really a heart attack can insure hospital for negligence I've called so many different people at hospital and not one can tell me how they determined it was a heart attack.