If I'm correct you target heart rate would be 136 BPM.
I'm not saying to go out and hit that right away, work up to it and make sure you Dr knows that you are working out a bit.
http://www.heart.org/HEARTORG/GettingHealthy/PhysicalActivity/FitnessBasics/Target-Heart-Rates_UCM_434341_Article.jsp
Just my humble opinion, using heart rate as a key performance indicator for cardio health is useless. When I was in the worst shape of my life my resting pulse was low 50s. It doesn't mean anything, there are so many factors that go into resting heart rate. It will also vary throughout the day (at least it should).
When I run, I use pace and/or cadence to measure performance. I also set my target goals on pace/cadence. Same with biking.
If you have a smartphone with GPS, try an app like mapmywalk. It will give you pace, and you can target that instead of heart rate.