When the heart beats too fast, it may not pump enough blood to the rest of the body. As a result, the organs and tissues may not get enough oxygen. In general, tachycardia may lead to the following signs and symptoms: 
Sensation of a racing, pounding heartbeat or flopping in the chest (palpitations)
Chest pain
Fainting (syncope)
Lightheadedness
Rapid pulse rate
Shortness of breath
 Some people with tachycardia have no symptoms. The condition may be discovered when a physical exam or heart tests are done for another reason.