Slow Heart Rate. Is the solution for it?

My brother has some heart problem. During his heart checkup we found that his heart beat went as low as 37 heartbeat/min once in a day. Doctors say this is dangerous, i read in google and found out that it is called Bradycardia (slow heart rate). But he doesn't have any symptoms related to that like he doesn't feel tired or he doesn't have chest pain. He just told that once or twice he blacked out in 1-2 years. He plays a lot. He used to cover 2-3 rounds of stadium by running. He is just 19 years old, is it possible for somebody so young facing heart issue. We have done thyroid check but its showing normal. Should we do Electrolytes imbalance checkup as well? He is very fit. Don't know how his heart beat is showing this much low. I read for athletes heartbeat can be low. Can it be this much low? What is the solution for it?