We Have A Family Friend Who Is 45 Healthy, But

We have a family friend who is 45 healthy, but in the last 2 years has had 3 different episodes where he has a rushing of blood pumping through his heart then his face gets supper hot and then he passes out and his heart stops beating until he is revived with CPR. He has been checked out at 2 different hospitals and they say it is not a heart attack or a stroke. They can not seem to find out why periodic episodes attack him out of the blue like this.