Is it safe to run at slow pace, although heart rate goes into 90% range (190+) after 10 min. Resting heart rate, BP and stress test are all normal.?

Running pace. Yes. Remember that you calculate the desired heart rate for exercise by the formula: 70% x (220 - yourage) as your target heart rate. Your maximal heart rate is just 220 minus yourage. As long as you don't exceed your maximal heart rate, you should be ok. With continued exercise, your pulse will trend lower during exercise.