Abnormal heart rhythms (arrhythmias) are caused by problems with the electrical system that regulates the steady heartbeat. The heart rate may be too slow or too fast; it may stay steady or become chaotic (irregular and disorganized). Some arrhythmias are very dangerous and cause sudden cardiac death, while others may be bothersome but not life threatening.
AFib is a type of heartbeat that is irregular or fast (rapid). If you have this condition, your heart beats without any order. This makes it hard for your heart to pump blood in a normal way. Having this condition gives you more risk for stroke, heart failure, and other heart problems. Atrial fibrillation may start all of a sudden and then stop on its own, or it may become a long-lasting problem. Although AFib isn't usually life threatening, it can lead to other rhythm problems, feeling tired all the time, and heart failure (with symptoms such as filling up with fluid, swelling of the hands, legs and feet, and shortness of breath).
Atrial flutter is similar to AFib because it also causes a fast beat in the atria. However, AFL is caused by a single electrical wave that circulates very rapidly in the atrium, about 300 times a minute. This leads to a very fast, but steady, heartbeat. It can also increase the risk of a stroke.
Sick sinus syndrome is not a disease, but a group of signs or symptoms that show that the heart's natural electrical pacemaker, the sinus node, is not working properly. In SSS, the heart rate can alternate between slow (bradycardia) and fast (tachycardia), often in combination with atrial fibrillationor atrial flutter. Treatment of SSS usually involves implanting a pacemaker, often along with medication.
A harmless faster rhythm, sinus tachycardia is a normal increase in heart rate that happens with fever, excitement, and exercise. There is no need for treatment, except in cases when it is caused by an underlying problem, such as anemia (a low blood count) or hyperthyroidism (overactive thyroid gland), or rarely, happens frequently and without a clear cause (inappropriate sinus Tachucardia).
Fainting, or feeling as if one might pass out, can be caused by serious heart rhythm disorders and needs to be evaluated carefully. Sometimes the cause is not heart related, as in cases of low blood sugar, but it can still be dangerous due to the risk of injuries from falling.
Sudden Cardiac Arrest (SCA) caused by ventricular fibrillation is the cause of half of all heart related deaths. In VF, the heartbeat is fast and chaotic, causing the lower heart chambers, or ventricles, to spasm. Sometimes, a heart attack (blockage of the heart pipes/arteries) can lead to VF. VF is sudden, happens without warning, and stops the heart from working.
When electrical signals from the upper chambers of the heart (atria) cannot travel to the lower chambers (ventricles), heart block happens. The lower chambers of the heart (ventricles) then beat too slowly, decreasing the amount of oxygen that gets to the body and brain. This causes a slow pulse and can result in a lack of energy, light headedness or Fainting.
Long QT Syndrome is a disorder of the electrical system. It can be inherited, brought on by taking certain medications, or caused by a combination of both. People with LQTS are at risk for VF, the most dangerous heart rhythm that causes sudden death.
Extra, early, or "skipped" beats are the most common cause of irregular heart rhythms. These can start in the upper or lower chambers of the heart (atrial or ventricular premature contractions).
A life-threatening arrhythmia, ventricular tachycardia is usually seen along with other serious heart disease but sometimes happens in people with normal hearts. Because VT can lead to ventricular fibrillation (a dangerously fast and disorganized heartbeat), it is a serious condition that needs aggressive treatment and follow up.
Supraventricular tachycardia, most commonly referred to as SVT, is a broad term and includes many different forms all with similar type of symptoms. SVT is the most common type of abnormal fast heart rhythms in children.