My Dad, who is in his seventies, has been living with this a similar condition for four or five years, now. He’s got atrial fibrillation. Your heart still beats, but there is a greater danger of stroke, and since you don’t have as good a blood flow, you get tired more quickly. My father takes lots of blood thinners, and has to be tested regularly and get his meds adjusted. The blood can’t be too thick or too thin. Too thin, and you can bleed out too easily (no clotting). Too thick and you get much higher risk of blood clots, which find their way into your brain, and get stuck, and voila! A stroke! They do have ways of attempting to treat the condition. One somewhat scary sounding one is when they stop your heart and then start it up again. My Dad said that if they do this, and then your heart reverts to the wrong beat, the shock probably won’t work again. There’s also an operation, I believe, but I’m not sure about that, and I don’t know how it works. Anyway, you can read more on any of the medical websites. This article about arrhythmia might be a good starting point. As I said, my father has atrial fibrillation. You might recognize the name of what your gf has from that article. However there’s a real good chance she will lead a full life, I would think. Don’t give up hope! It is scary. And it’ll be scary until you see that she is surviving. There’s a very good chance she has a long life ahead of her, although it may be a modified life. It is doubtful that she will ever climb Mt. Everest, now.