Tachycardia is caused by something that disrupts the normal electrical impulses that control the rate of your heart's pumping action. Many things can cause or contribute to problems with the heart's electrical system. These factors include:
Damage to heart tissues from heart disease
Anemia
Exercise
Sudden stress, such as fright
High blood pressure
Smoking
Fever
Drinking too many caffeinated beverages
Medication side effects
Imbalance of
electrolytes, mineral-related substances necessary for conducting electrical impulses
Overactive
thyroid (hyperthyroidism)...mainly thyroid issues... consult physician they will help you