Arrhythmias differ from normal heartbeats in speed or rhythm. Arrhythmias are also grouped by where they occur—in the upper chambers of the heart, in its lower chambers, or between the chambers. The main types of arrhythmia are bradyarrhythmias; premature, or extra, beats; supraventricular arrhythmias; and ventricular arrhythmias.
To understand arrhythmia, it helps to understand how your heart’s electrical system works. Arrhythmias known as conduction disorders are covered separately.
Bradyarrhythmia is a slow arrhythmia in a heart that beats too slowly—a condition called bradycardia. For adults, this means slower than 60 beats per minute. Some people, especially people who are young or physically fit, may normally have slow heart rates. For them, bradycardia is not dangerous and does not cause symptoms.
Premature or extra heartbeat
A premature heartbeat happens when the signal to beat comes early. It can feel like your heart skipped a beat. The premature, or extra, heartbeat creates a short pause, which is followed by a stronger beat when your heart returns to its regular rhythm. These extra heartbeats are the most common type of arrhythmia. They are called ectopic heartbeats and can trigger other arrhythmias.
Arrhythmias that start in the heart’s upper chambers, called the, or at the gateway to the lower chambers are called supraventricular arrhythmias. Supraventricular arrhythmias are known by their fast heart rates, or tachycardia. Tachycardia occurs when the heart, at rest, goes above 100 beats per minute. The fast pace is sometimes paired with an uneven heart rhythm. Sometimes the upper and lower chambers beat at different rates.
Types of supraventricular arrhythmias include:
- Atrial fibrillation. This is one of the most common types of arrhythmia. The heart can race at more than 400 beats per minute.
- Atrial flutter. Atrial flutter can cause the upper chambers to beat 250 to 350 times per minute. The signal that tells the upper chambers to beat may be disrupted when it encounters damaged tissue, such as a scar. The signal may find an alternate path, creating a loop that causes the upper chamber to beat repeatedly. As with atrial fibrillation, some but not all of these signals travel to the lower chambers. As a result, the upper chambers and lower chambers beat at different rates.
- Paroxysmal supraventricular tachycardia (PSVT). In PSVT, electrical signals that begin in the upper chambers and travel to the lower chambers cause extra heartbeats. This arrhythmia begins and ends suddenly. It can happen during vigorous physical activity. It is usually not dangerous and tends to occur in young people.
These arrhythmias start in the heart’s lower chambers. They can be very dangerous and usually require medical care right away.
- Ventricular tachycardia is a fast, regular beating of the ventricles that may last for only a few seconds or for much longer. A few beats of ventricular tachycardia often do not cause problems. However, episodes that last for more than a few seconds can be dangerous. Ventricular tachycardia can turn into other more serious arrhythmias, such as ventricular fibrillation, or v-fib.
- Ventricular fibrillation occurs if disorganized electrical signals make the ventricles quiver instead of pumping normally. Without the ventricles pumping blood to the body, sudden cardiac arrest and death can occur within a few minutes. Torsades de pointes is a type of arrhythmia that causes a unique pattern on an EKG and often leads to v-fib.