Low pulse rate does not always require some action. UNLESS you are symptomatic. My father has had a low pulse rate (40's) for years and years and doctors have not needed to do anything because he is not showing any signs of problems (eg blacking out, tiredness). That is just how is body is and has become accustomed to it. However he did have a pacemaker put in since he developed a Hernia and no hernia surgeon would touch him if he had that low a pulse rate. So since you have experienced a black out episode, I would consider a pacemaker. By the way, my father does say it was the best thing he did by putting in the pacemaker since it was quick, painless and now he doesn't worry about his pulse.
Normal is between 60-100. You probably need a pacemaker, I'm 27 and I have one but my rate was going into the 30s, so I would suggest seeing a cardiologist. For your age and having a blackout I wouldnt put it off any longer. Plus, 50 is the lowest you know of it going. You'll need to wear a monitor for days to see what its doing all the time. Chances are it may be going even lower. The blackout is the key here, if it was in the 50s and you felt fine, they might not rush into anything but when you're blacking out, thats not ok.
Good luck