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There are several types of heart arrhythmias depending on which part of the heart or nerve pathway is damaged.

Premature Contractions

Premature or early contractions are extra contractions that begin somewhere in the heart muscle instead of the nerve pathway. These extra contractions beat out of sync with the rest of the heart and disrupt the normal rhythm of the heart. Premature contractions will occur randomly in most people at some point in their life and are usually harmless. In fact, most people are unaware they have them. Occasionally, premature contractions may cause someone to feel a flutter, a skipped beat, or jumping in the chest. Premature contractions that occur more often or occur in people with heart disease may need treatment or monitoring.

Premature contractions may be:

Premature Supraventricular Contractions

Premature supraventricular contractions or premature atrial contractions (PAC) occur in the upper chambers of the heart. Premature beats may make the rest of the heart beat before it should.

Premature Ventricular Complexes

Premature ventricular complexes (PVC) are premature contractions in lower chambers of the heart. They may create the feeling of a pause before the next rhythmic contraction of the ventricle.

In some people, premature heartbeats occur because of stress, caffeine, tobacco, or heart-related conditions.

In some people, premature heartbeats occur because of stress, caffeine, tobacco, or heart-related conditions.

Sinoatrial Node Arrhythmias

The sinoatrial (SA) node keeps the heart beating at a regular rhythm of 60-100 beats per minute. Problems with the SA node can lead to arrhythmias such as:

Sinus Arrhythmia

Changes in the heart rate that occurs during breathing. The heart rate increases with inhale of breath and slows down when air is exhaled from lungs. It occurs because of stimulation of the vagus nerve during breathing. The vagus nerve can impact the heart rate. This arrhythmia is common in children and often found in adults, but is generally harmless.

Sinus Tachycardia

The SA node causes the heart to beat at a faster rate than normal (more than 100 beats per minute). Tachycardia may be a temporary and in normal response to physical activity or a stressful situation. Sometimes the tachycardia may begin or continue because of stimulants such as caffeine, smoking, or certain medications.

Sick Sinus Syndrome

The SA node does not fire its signals in a regular rhythm. This may cause heart rate that is too slow, too fast, or one that alternates between too slow and too fast. The rhythms are also marked with long pauses. The risk for this syndrome increases with age. A pacemaker may eventually be needed to manage the heart rate.

Supraventricular/Atrial Arrhythmias

These types of arrhythmias occur in the atria, the upper chambers of the heart. Types of supraventricular arrhythmias include:

Atrial Fibrillation

Atrial fibrillation (AF or AFib) is the most common type of heart arrhythmia. It occurs when the atria contract in a fast and erratic manner, making the muscle look like it is quivering. The atria's job is to push blood into the ventricles before they contract. If the atria are beating faster than the ventricles, the ventricles can not completely fill with blood. This can decrease the amount of blood available to push out to the body. Some people have AF without any symptoms. In those that have them, AF can cause palpitations, shortness of breath, lightheadedness, or cognitive impairment . If you have these symptoms, talk to your doctor.

People with AF also have an increased risk of stroke or heart attack . Irregular contractions of the atria can cause blood to pool in the atria, which can lead to blood clots. These clots can travel to the brain and cause a stroke. The extra stress on the heart because of poor blood flow from the atria to the ventricle can also eventually lead to heart failure .

Atrial Flutter

Atrial flutter is also very fast contraction of the atria, but unlike fibrillation, the contractions have a regular rhythm. Atrial flutter contractions are more organized than AF, but the risks, complications, and symptoms are the same.

Paroxysmal Supraventricular Tachycardia

In paroxysmal supraventricular tachycardia (PSVT), repeated periods of very fast heartbeats begin and end suddenly. It is caused by a malfunction of the electrical connection above the ventricles. Some may be brief and not require treatment. Others are regular and persistent, causing symptoms such as chest pain, lightheadedness, or weakness. These symptoms may require treatment.

Ventricular Arrhythmias

Ventricular arrhythmias occur in the lower chambers of the heart, the ventricles. The ventricles push blood throughout the body and to the lungs, so ventricular arrhythmias can cause very serious symptoms. These arrhythmias are considered medical emergencies because they may lead to sudden cardiac arrest and/or death. Ventricular arrhythmias include:

Ventricular Fibrillation

Rapid and erratic contraction in the ventricles. This causes the heart to make quivering-like motions that make it impossible to pump blood to the rest of the body. Ventricular fibrillation is a primary cause of sudden cardiac death.

Ventricular Tachycardia

The heart beats faster than normal. Tachycardia is a normal response to physical activity, but tachycardia that starts without cause or continues even at rest, suggests a problem. A rapid heartbeat makes it difficult for the ventricles to fill with blood between heartbeats. This reduces the amount of blood that can be pumped out to the body or lungs.

Long QT Syndrome

QT is the name given to a section of an electrocardiogram (EKG) reading. It reflects the electrical activity of the lower chambers of the heart. Long QT syndrome is when it takes longer than expected to complete QT section. It indicates a problem with how the electrical signal is moving through the ventricles. The long QT interferes with the heart's rhythms and can lead to serious heart arrhythmias. People with long QT syndrome are also prone to fainting spells and palpitations.

Nerve Conduction Problems

Heart Block

Heart block can occur anywhere along the heart’s electrical pathway from the SA node to the bundle branches. It may be completely asymptomatic or it may cause your heart rate to slow down, possibly resulting in lightheadedness, which can lead to fainting. It may also feel like your heart is skipping beats.

Heart block can occur anywhere along the heart’s electrical pathway from the SA node to the bundle branches. It may be completely asymptomatic or it may cause your heart rate to slow down, possibly resulting in lightheadedness, which can lead to fainting. It may also feel like your heart is skipping beats.

Wolff-Parkinson-White Syndrome

Wolff-Parkinson-White (WPW) syndrome occurs when electrical signals arrive at the ventricles too soon and are transmitted back into the atria. Very fast heart rates may develop as the electrical signal ricochets between the atria and ventricles. WPW syndrome is more serious and can be life-threatening.

Revision Information

  • Atrial fibrillation. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated February 11, 2014. Accessed March 18, 2014.

  • Atrial fibriallation(AF or Afib). American Heart Association website. Available at: http://www.heart.org/HEARTORG/Conditions/Arrhythmia/AboutArrhythmia/Atrial-Fibrillation-AF-or-AFib%5FUCM%5F302027%5FArticle.jsp. Updated March 12, 2014. Accessed March 18, 2014.

  • Atrial flutter. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated August 8, 2013. Accessed March 18, 2014.

  • Goel R, Srivathsan K, et al. Supraventricular and ventricular arrhythmias. Prim Care. 2013;40(1):43-71.

  • Overview of arrhythmias. Merck Manual of Diagnosis and Therapy website. Available at: http://www.merckmanuals.com/professional/cardiovascular%5Fdisorders/arrhythmias%5Fand%5Fconduction%5Fdisorders/overview%5Fof%5Farrhythmias.html. Updated July 2012. Accessed March 18, 2014.

  • Sudden cardiac arrest. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated February 3, 2014. Accessed March 18, 2014.

  • Types of arrhythmia. National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/health/health-topics/topics/arr/types.html. Updated July 1, 2011. Accessed March 18, 2014.