Table of Contents
c. Paroxysmal Supraventricular Arrhythmia (PSVT)
d. Wolff-Parkinson-White Syndrome
VI. Arrhythmias of the Ventricles
b. Ventricular Fibrillation (VFib)
What is Arrhythmia?
Arrhythmia is defined as a condition in which the heart beats with an irregular or abnormal rhythm. Changes or damages to heart tissue may cause arrhythmia. A disruption in the electrical signals that control your heartbeat may also cause arrhythmia.
Many different types of arrhythmias are grouped by where they occur in the heart. Some arrhythmias start in the atria (upper chambers) of the heart, and others begin in the ventricles (lower chambers) of the heart. Some arrhythmias may occur between these upper and lower chambers. Tachycardia is a condition in which the heart beats too quickly, and bradycardia is a condition where the heart beats too slowly. A premature heartbeat is another form of arrhythmia, and it can feel like your heart skipped a beat.
Below is a computer-generated cross-section 3D model of the heart beating naturally without any arrhythmias. As you can see, the sinoatrial node sends an electrical signal to the upper chambers (atria) to contract at the same time. As the atria contract blood is pushed through valves into the lower ventricles. The lower ventricles then contract and send blood throughout the rest of the body.
Treatment for Arrhythmias
Treatment for arrhythmias of the atria and ventricles may be different. The type of arrhythmia and seriousness of the condition will determine treatment methods. In atrial fibrillation, for example, the heart may return to its natural rhythm and require no treatment. Electrical cardioversion (an electric shock to the heart to restore its natural rhythm) and ablation techniques (destruction of particular heart tissue that causes abnormal electrical activity) are sometimes used to treat atrial arrhythmias.
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Many individuals with atrial arrhythmias can be treated with heart rate-controlling medications such as beta-blockers (Metoprolol, Nadolol) calcium channel blockers (Amlodipine, Diltiazem), sodium and potassium channel blockers, glycosides, blood-thinners (Dabigatran, Rivaroxaban), or other heart rhythm medications (Multaq).
Ventricular arrhythmias most often are a medical emergency that requires immediate treatment. Treatment for ventricular fibrillation includes the use of a defibrillator to provide an electric shock to the heart and to prevent cardiac arrest.
Bradyarrhythmia, also called bradycardia, is a condition characterized by a slow heart rate, typically less than 60 beats per minute. Some experts define bradycardia as a heart rate of fewer than 50 beats per minute at rest. For some people, a slow heart rate is a sign of being very physically fit. For others, a slow heart rate is a sign of a problem with the heart's electrical system.
Bradycardia can be a result of damage to the heart, causing problems to the sinoatrial node (the heart’s pacemaker) or disruptions in other electrical pathways of the heart. Damage to the heart may be because of coronary heart disease, genetics, medication, congenital conditions, or aging.
Premature (Extra) Beats
Premature beats are quite common. Often this form of arrhythmia provides no symptoms, but when symptoms do occur, it can feel like the heart is racing, pounding, or has skipped a beat. A premature heartbeat occurs when the signal for a beat arrives too early. As the heart's upper chambers contract a few moments earlier than they should, they then rest an instant longer afterward to regain a natural rhythm. This momentary pause after a premature contraction is what creates the feeling of a skipped beat. Most often, premature beats are harmless, especially in healthy people. However, it is important to note that the feeling of an abnormal heartbeat can be a warning sign of a heart rhythm problem.
Arrhythmias of the Atria
Arrhythmias that start in the two upper chambers of the heart — the atria — are called supraventricular arrhythmias. Supraventricular arrhythmias are tachycardias. Tachycardia is characterized by a fast heart rate that, at rest, increases to above 100 beats per minute and can be paired with uneven heart rhythm. The types of supraventricular arrhythmias include atrial fibrillation (AFib), atrial flutter, paroxysmal supraventricular tachycardia (PSVT), and Wolff-Parkinson-White (WPW) syndrome.
Atrial Fibrillation (AFib)
Atrial fibrillation (Afib) is the most common type of severe arrhythmia characterized by a very fast and irregular rhythm that originates in the atria. It is estimated that between 2.7 to 6.1 million Americans have AFib.  At its maximum, AFib can cause the heart to race more than 400 beats per minute. 
The sinoatrial (SA) node is located in the upper atria and is responsible for sending out electrical signals that keep the heart beating properly; it is known as the pacemaker of the heart. In AFib, electrical signals begin firing in other parts of the atria other than the SA node. When this happens, the electrical signals get jumbled and spread about the atria in a disorganized manner. This sequence of events then causes the atria walls to fibrillate (twitch) rather than beating normally. What is distinct in AFib is that the atria beat irregularly or at different times, as opposed to a healthy heart where the atria beat in sync. Ultimately, in AFib, the atria are no longer able to contract together or pump blood to the ventricles, increasing the risk for a blood clot, stroke, and heart failure.
In a healthy heart, the top chambers (atria) contract at the same time to push blood into the bottom chambers (ventricles). The main difference between AFib and atrial flutter is in the timing of atrial contractions. In atrial flutter, the atria beat regularly, but faster and more often than normal. For every one ventricular beat, you could have four atrial beats. 
Damaged tissue, such as a scar, may disrupt the normal signal that tells the upper chambers to beat at a certain rate. This disruption may create a looping-pathway that tells the upper chambers to beat continuously. The lower ventricles may not receive the same signals as the upper atria, causing the two chambers to beat at different rates. Atrial flutter can cause the upper chambers to beat as fast as 250 to 350 times per minute.
Atrial flutter is less common than AFib but has similar symptoms such as feeling faint, tiredness, heart palpitations, and shortness of breath. Atrial flutter also carries complications such as the increased risk of stroke and blood clots.
Paroxysmal Supraventricular arrhythmia (PSVT)
Paroxysmal supraventricular arrhythmia (PSVT); try saying that ten times fast! A PVST begins and ends quite suddenly and is characterized by a speedy heart rate. This arrhythmia occurs because of problems with the electrical-signaling connection between the upper (atria) and lower (ventricles) chambers of the heart.
Because of this disconnection between upper and lower, the signals that begin in the atria and travel to the lower ventricles may end up reentering the atria once again, causing extra heartbeats. This type of arrhythmia often occurs in younger people during exercise and is usually not dangerous.
Wolff-Parkinson-White Syndrome (WPW) is a special type of PSVT. In WPW, electrical signals travel from the atria to the ventricles along an extra pathway. Because of the extra pathway, the heart's normal electrical-signaling gets disrupted, causing the ventricles to beat very fast. WPW can be life-threatening.
Arrhythmias of the Ventricles
Now that we’ve discussed arrhythmias associated with the upper chambers of the heart (atria), we will explain the handful of rhythm disorders related to the two lower chambers of the heart, the ventricles. A ventricle is one of two chambers, larger than the atria, toward the bottom of the heart. Ventricles collect blood from the upper atria and then send this blood into the lungs and the rest of the body. Ventricular arrhythmias start in the electrical signaling pathways of the ventricles and can be extremely dangerous. 
Tachycardia refers to a heart rate that is too fast. In ventricular tachycardia, the ventricles beat very fast, which usually lasts only a few seconds and does not always cause problems. Episodes of this condition lasting longer than a few seconds can be very dangerous and may turn into other harmful arrhythmias such as ventricular fibrillation.
Ventricular Fibrillation (VFib)
Rather than pumping blood normally, in ventricular fibrillation, disorganized electrical signals cause the ventricles to quiver or twitch. The quivering ventricles are no longer able to pump blood throughout the body and may cause a person to lose consciousness or die within a few minutes. Immediate treatment of VFib is essential. Experts believe many sudden cardiac arrest deaths are due to VFib. Treatment of VFib requires immediate defibrillation (an electric shock to the heart). VFib may occur in a weak heart muscle due to another condition or after a heart attack.
Torsades de Pointes
Torsades de pointes translates as “twisting of the points” and is a specific form of VFib. Certain medications, such as antibiotics and antipsychotic drugs, and an imbalance of potassium, calcium, and magnesium in the bloodstream, can cause this type of arrhythmia. Torsade de Pointes can also be caused by long QT syndrome, which is characterized by abnormal intervals between certain heart waves measured by an EKG (electrocardiogram). 
Atrial and ventricular arrhythmias can range from mild to life-threatening conditions. Although reading about arrhythmias and your particular condition may feel overwhelming, it’s empowering to focus on the things that are within your control. Learn more about lifestyle changes that can help with atrial fibrillation, including tips for managing stress, exercise, and a heart-healthy diet. (Link to “Lifestyle Tips for Atrial Fibrillation” article).
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