Definition:
A heart rate over 100 beats a minute is known as tachycardia. Some tachycardias are relatively benign and need no treatment, but others can be life-threatening.
Diagnosis:
Tests that monitor the heart rate -- such as electrocardiogram (ECG), holter monitor, and event monitor -- can help in diagnosing tachycardia.
Treatment:
Treatment of tachycardia is typically directed at chemical conversion (with antiarrhythmics), electrical conversion (giving external shocks to convert the heart to a normal rhythm) or use of drugs to simply control heart rate (for example as in atrial fibrillation).
Symptoms and Signs:
Some symptoms include: dizzines, shortness of breath, lightheadness, rapid heartbeat, heart palpitation, chest pain, blackouts, visual problems, and fainting (syncope).
Causes:
An increase in sympathetic nervous system stimulation can lead the heart rate to increase, both by the direct action of sympathetic nerve fibers on the heart and by causing the endocrine system to release hormones such as epinephrine (adrenaline), which have a similar effect. Increased sympathetic stimulation is generally due to physical or psychological stress (the so-called "fight or flight" response), but can also be induced by stimulants such as amphetamines.
