Types of Arrhythmias
Two major types of arrhythmias are tachycardias (the heartbeat is too fast -- more than 100 beats per minute), and bradycardia (the heartbeat is too slow -- less than 60 beats per minute).
Arrhythmias can be life-threatening if they cause a severe decrease in the pumping function of the heart.
When the pumping function is severely decreased for more than a few seconds, blood circulation is essentially stopped, and organ damage may occur within a few minutes. Life-threatening arrhythmias include ventricular tachycardia and ventricular fibrillation.
Arrhythmias are identified by where they occur in the heart (atria or ventricles) and by what happens to the heart's rhythm when they occur.
Arrhythmias that start in the atria are called atrial or supraventricular (above the ventricles) arrhythmias. Ventricular arrhythmias begin in the ventricles. Ventricular arrhythmias are usually caused by heart disease are very serious.
Arrhythmias Originating in the Atria
- Atrial fibrillation: In atrial fibrillation, the electrical activity of the heart is uncoordinated, with electricity traveling about the upper chambers in a chaotic fashion, causing the upper chambers to quiver (like a "bag of worms") and contract inefficiently or not at all. Atrial fibrillation is common particularly in the elderly and those with heart disease. It is also common in patients with heart valve disease who may require surgery to repair or replace the mitral valve. There are a variety of treatment options for atrial fibrillation, including drugs, an ablation -- a non-surgical technique which eliminates the abnormal heart tissue with a catheter, or surgery in some cases.
- Atrial flutter: Atrial flutter causes a rapid but coordinated electrical stimulation of the upper chamber of the heart, often leading to a rapid pulse. The atria are stimulated so quickly that they can not contract or squeeze. This arrhythmia is due to a loop of electricity in the upper chambers of the heart. It is often curable with ablation.
- Supraventricular tachycardias (PSVT): This is a fast heart rhythms from the top part of the heart. In this condition, repeated periods of very fast heartbeats begin and end suddenly. These arrhythmias are usually due to extra connections between the upper and lower chambers of the heart. They are ofted difficult to control with medication and are often curable with an ablation.
- Wolff-Parkinson-White syndrome: This is a special type of PSVT. This syndrome involves episodes of a rapid heart rate (tachycardia) caused by abnormal electrical connection in the heart. In people with Wolff-Parkinson-White syndrome, there is an extra (accessory) connection between the top and bottom chambers of the heart. Wolff-Parkinson-White occurs in approximately 4 out of 100,000 people, and is one of the most common causes of fast heart rate disorders (tachyarrhymthmias) in infants and children.
- Premature supraventricular contraction or premature atrial contraction (PAC): Premature beats or extra beats frequently cause irregular heart rhythms. Those that start in the upper chambers are called premature atrial contractions (PACs). These are quite common and are benign. Usually no cause can be found and no special treatment is needed.
- Sick sinus syndrome: The sinus node (heart's pacemaker) does not fire its signals properly, so that the heart rate slows down. Sometimes the rate changes back and forth between a slow (bradycardia) and fast (tachycardia) rate. This most often occurs in the elderly as a result of degenerative changes to the conduction pathways of the heart.
- Sinus arrhythmia: Cyclic changes in the heart rate during breathing. Common in children and often found in normal, healthy adults. A pacemaker may be required for treatment.
- Sinus tachycardia: The sinus node sends out electrical signals faster than usual, speeding up the heart rate. This is a normal response to exercise.
- Multifocal atrial tachycardia: In multifocal atrial tachycardia (M.A.T.), multiple locations within the atria "fire" and initiate an electrical impulse. Most of these impulses are conducted to the ventricles, leading to a rapid heart rate, anywhere from 100 to 250 beats per minute. M.A.T. is most common in people 50 years old and over and it is often seen in patients with lung disease.
Arrhythmias Originating in the Ventricles
- Premature ventricular contraction (PVC): An electrical signal from the ventricles causes an early heartbeat that generally goes unnoticed. The heart then seems to pause until the next beat of the ventricle occurs in a regular fashion. These are commonly detected in normal, healthy adults.
- Ventricular Fibrillation is where electrical signals in the ventricles fire in a very fast and uncontrolled manner. This causes the lower chambers to quiver, and not pump blood. If the person does not receive immediate medical attention and a normal rhythm is not restored quickly, the patient will suffer brain and heart damage and die. Patients who survive this should have a defibrillator (ICD) implanted.
- Ventricular Tachycarida is a rapid, regular heartbeat arising in the ventricles, the bottom chamber of the heart. When it occurs, it's usually fatal. About 400,000 people a year die from it. The treatment of choice for this invariably includes an implantable defibrillator and or medication and or interventions like ablation to try to minimize or limit the number of shocks.
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This page was last updated: June 14, 2013