@turquoise-- I'm very sorry to hear that. My father suffered from that many years ago. If there is nothing wrong with his heart, it's probably a viral infection.
That was the cause of my dad's sharp chest pain. Doctors found that he had a mononucleosis infection. He didn't get treated in time and the virus settled in the heart tissue causing inflammation.
It takes some time to heal from myocarditis but anti-inflammatory medication and rest are all that's needed. Sometimes blood pressure medications might be given until the inflammation disappears. I hope your brother gets better soon.