Do symptoms like tachycardia go away quickly?

Type of tachycardia? Depends on how fast your heart rate is & why it's fast. Maximum normal heart rate depends on age: up to 200 in teenagers, about 150 by age 70. Recovery of normal hr following exercise is an indication of your state of fitness and the health of your heart. While abnormal heart rhythms may terminate suddenly, normal heart rhythms slow down over several minutes. Rapid hr may persist for many reasons.