Definitely get checked out to be safe. And try to get clarification on the supposedly having had a small heart attack--occasionally an EKG can show something when that really isn't the case. 22 is awfully young for something like that, especially for a woman--not saying it isn't possible but it does seem improbable. What was the arrhythmia you had? That could be what's going on here. Does the high heart rate start and stop suddenly, or gradually, and is it at all irregular? And some of us just seem to get our heart rates through the roof on hills--I certainly do when running (can hit or exceed 200 at times) so it could just be that as well.