context: Tachycardia is a condition that makes your heart beat more than 100 times per minute. There are three types of it: Supraventricular. This happens when the electrical signals in the organ's upper chambers misfire and cause the heart rate to speed up. It beats so fast that it can't fill with blood before it contracts. That reduces blood flow to the rest of your body. Ventricular. This is a rapid heart rate that starts in your ticker's lower chambers. It happens when the electrical signals in these chambers fire the wrong way. Again, the heart beats so fast that it can't fill with blood or pump it through the rest of your body. Sinus tachycardia. This happens when your heart's natural pacemaker sends out electrical signals faster than normal. Your ticker beats fast, but it beats the way it should. Any number of things. Strenuous exercise, a fever, fear, stress, anxiety, certain medications, and street drugs can lead to sinus tachycardia. It can also be triggered by anemia, an overactive thyroid, or damage from a heart attack or heart failure. Supraventricular tachycardia is most likely to affect people who smoke, drink too much alcohol, or have a lot of caffeine. In some cases it's linked to heart attacks. It's more common in women and children. The ventricular type is tied to more serious heart disorders, like lack of oxygen, and could also be associated with other conditions, such as sarcoidosis. It causes the skin and other body tissues to swell. It is also associated with abnormal electrical pathways which are present at birth (long QT), structural problems of the heart such as a cardiomyopathy, medications, or electrolyte imbalance. Sometimes, the reason is unclear. No matter which type of tachycardia you have, you may feel: Dizziness Lightheadedness Shortness of breath Chest pain Heart palpitations In extreme cases, you could become unconscious or go into cardiac arrest. But sometimes, a super-fast heart rate causes no symptoms at all. These may include: Electrocardiogram ( ECG or EKG). This records the electrical activity in your heart and helps your doctor search for things that don't look normal. You may have to wear a holter monitor, a portable machine that records your ECG signals over 24 hours. Exercise stress test. Your doctor will have you walk on a treadmill while he monitors your heart activity. Magnetic source imaging: This measures the heart muscle's magnetic fields and looks for weaknesses. Your doctor will decide what's best after he gets your test results. If you have sinus tachycardia, he'll help you pinpoint the cause and suggest things to lower your heart rate. These might include lifestyle changes like easing stress or taking medicine to lower a fever. If you have supraventricular tachycardia, your doctor may recommend that you drink less caffeine or alcohol, get more sleep, or quit smoking. Treatments for ventricular tachycardia may include medication to reset the heart's electrical signals or ablation, a procedure that destroys the abnormal heart tissue that is leading to the condition. Your doctor might also use a defibrillator to disrupt rapid heart rhythms. A rapid heart rate doesn't always need treatment. But sometimes it can be life-threatening. So play it safe -- let your doctor know right away if you have any type of irregular heartbeat.