That said, I am sorry for your loss and it is too bad your friend didn't have chest pains or some other symptom that would have led to a heart cath, which would surely have saved his life.
Also, unfortunately, all to many people lie to Doctors when they are asked if they have chest pains or shortness of breath, and a lot of people attribute the shortness of breath to simply getting older and fail to mention it to their docs.
Or if you fail a stress test - highly recommended if there is a history of heart disease in your family. This disease is also known as 'the silent killer' because most people either don't have symptoms before the heart attack or they attribute them to other conditions. Pain can occur anywhere in the body, one guy went to a dentist thinking he had a toothache, turned out he was having a heart attack.
He had been stabbed in a robbery while working at South Lake Tahoe. He had lost the feeling and most of the use of his left arm. So if there were any pains he never would have felt them.