Unless you have an abnormally high heart rate, I don't think someone your age and level of fitness could have sustained 178 BPM average for a bit over an hour. (No offense meant.) Especially since you weren't "out of breath."

Now if that WAS your average heart rate and your monitor is accurate, you should probably get that checked out.

While the formula 220-age isn't that accurate, it gives a good estimate for what your max heart rate should be. Max heart rate will be achieved when you're running as hard as you can up a steep hill multiple times until you are about to fall over from lack of oxygen.

Can you post the heart rate graph? (Heart rate vs. time?)

I've heard tech fabrics can cause bad readings with HR monitors. (Static electricity)