How dangerous is high pulse rate of heart?

May be very dangerou. There are many reasons for a very rapid heart rate. Some may be quite serious and even life threatening You should see your physician and be evaluated with EKG and other tests.
Abnormal tachycardia. Average resting heart rates in healthy people can range from the 50s to 70s, so an average resting heart rate of over 80 is usually considered abnormal. See a doctor for evaluation soon.

Related Questions

What is harder on heart: high pulse rate and high blood pressure?

Both can be. This depends on your individual risks. Diet and exercise can lower both, but this can take awhile. Medications also work. You should talk with your doctor. Read more...