Tachycardia, also called tachyarrhythmia, commonly defined  as a  heart rate increase than normal rate, making your heartbeat more than 100 times per min.

Causes:
• Strenuous exercise
• Fever
• Fear
• Stress
• Anxiety
• Certain medications

There are 3 types:

• Supraventricular– Supraventricular tachycardia is a rapid heartbeat that originates above the ventricles in the atria, impulses originating above the ventricles.
• Ventricular– rapid heart rhythm that starts in the lower part of the heart (ventricles).
• Sinus tachycardia – elevated sinus rhythm characterized by an increase in the rate of electrical impulses arising from the senatorial node.

Symptoms:
• Shortness of breath
• Lightheadedness
• Rapid pulse rate
• Heart palpitations 
• Chest pain
• Fainting