What is an Arrythmia?

What is an Arrhythmia?

An arrhythmia is an abnormality of the heartbeat. The heart could beat too fast, too slow, skip a beat, or beat irregularly.

Why do Arrhythmias Occur?

A variety of conditions can trigger arrhythmias. Those with heart disease are more prone to arrhythmias, however, some arrhythmias may occur in people with no apparent heart disease. It is important to identify any underlying heart disease, family history of arrhythmias, or role of medications as a cause for an arrhythmia in an individual patient.

What are the Different Types of Arrhythmias?

Arrhythmias are broadly classified based upon their site of origin or abnormality in the heart.

Originating in the atrium:

Sick Sinus Syndrome
Sick Sinus Syndrome (SSS) or Sinus Node Dysfunction results from a malfunctioning SA Node, the natural pacemaker of the heart. It usually presents as an inappropriately slow heart rate and may cause weakness, fatigue, or syncope (fainting). Occasionally, it can present as rapid heart beat, e.g. atrial fibrillation.

SSS occurs due to Hypertension (high blood pressure), Coronary Artery Disease (clogging of the arteries of the heart), or degenerative disease of the node as a result of aging or other unclear reasons. Certain medications, such as beta-blockers or calcium channel blockers, can often cause or worsen the symptoms of SSS.

SSS is easily treated with permanent pacemakers. It accounts for over half of all permanent pacemakers implanted in the United States.

Premature Atrial Contractions (PAC's)
Sometimes, a different site in the atrium starts a cardiac impulse before the normal beat. The natural pause following this early beat gives the patient the feeling of a "skipped beat".

Conditions such as increased caffeine or alcohol intake, stress, or infections can cause PACs. Usually, PACs do not need treatment.

Paroxysmal Supraventricular Tachycardia
(SVT or often called PAT)
This occurs when an abnormal site in the atrium causes a fast heartbeat. Such arrhythmias often start and end suddenly, but may need intervention if they persist.

There are various types of SVT:

1. Atrial Flutter
Atrial flutter is a regular rapid heartbeat (tachycardia) resulting from abnormal circuit in the right atrium (upper chamber). This arrhythmia usually occurs in the setting of an underlying diseased heart. Untreated, atrial flutter can lead to atrial fibrillation, palpitations, shortness of breath, heart failure or fainting (syncope). It is highly curable by radiofrequency ablation.

2. Atrial Fibrillation
Atrial fibrillation is the commonest form of rapid heart rhythm in hospitalized patients in which the heart beats rapidly and irregularly due to the cardiac impulse originating from several abnormal pacemakers in the atria (upper chambers).

While atrial fibrillation can occur in some people without apparent heart disease, it is usually seen in the presence of hypertension (high blood pressure), coronary artery disease, valvular heart disease, or thyroid gland disease.

Atrial fibrillation can potentially cause several problems:

• The rapid heart rate can cause palpitations, shortness of breath, weakness, fainting, heart failure, or ultimately cause weakening of the heart pump.

• Pooling of blood in the atria can cause clots to form in them. These clots can break off, and go via the bloodstream to the brain and other vital organs causing catastrophic events like strokes.
  

Treatment involves:

• Initial control of heart rate - medications are usually effective.

• Anticoagulation (blood thinning) to prevent formation of blood clots - your doctor will advise you how long you may need this.

• Conversion of atrial fibrillation to normal heart rhythm - medications and/or electric shock (cardioversion) may be necessary.

• Prevention of future episodes - medications or radiofrequency ablation.

3. Wolff-Parkinson-White Syndrome
WPW Syndrome occurs as a result of an extra connection (accessory pathway) between the atria (upper chambers) and the ventricles (lower chambers) that developed prior to birth.

Patients with WPW Syndrome become aware of episodes of rapid heartbeat usually later in life. Often straining, gagging, vomiting, or massaging the artery in the neck can terminate these episodes.

This is potentially a curable condition by radiofrequency ablation of the accessory pathway, and there is usually no need for lifelong medication.

4. AV Nodal Reentrant Tachycardia (AVNRT)
AVNRT occurs due to an extra connection through the AV node creating a circular circuit and episodes of rapid heartbeat. This condition is readily curable by radiofrequency ablation.

5. Sinus Arrhythmia
This occurs from a variation in heart rate with breathing. Often seen in teenagers and young adults, this arrhythmia rarely needs further evaluation.

Arrhythmias originating in the atrioventricular (AV) node:

Heart Block
When there is a delay or blockage of the electrical impulse in the normal conduction pathway, the condition is called a heart block. The commonest site of heart block is the AV Node and the His-Purkinje system. Usually, heart block leads to slow heart rate and symptoms like weakness, tiredness and fainting (syncope). Such patients usually need permanent pacemaker implantation.

Originating in the Ventricles (lower chambers):

Premature Ventricular Complexes (PVC)
PVCs are electrical impulses that arise early within the ventricles and cause a "skipped beat". They may be seen in people with or without heart disease.

Ventricular Tachycardia
This results from a series of rapidly firing electrical impulses or due to the creation of electrical short circuits arising from within the ventricles. Often, the resultant ventricular contractions are ineffective in pumping enough blood to vital organs like the brain leading to symptoms like dizziness, fainting, and sometimes cardiac arrest. This is a serious arrhythmia and is usually due to underlying scarring in the ventricles as a result of previous heart attack, or heart muscle damage.

Ventricular Fibrillation
Ventricular fibrillation is similar to ventricular tachycardia except in that the rate of firing is even faster resulting in the heart's quivering rather than pumping blood. Unless treated promptly, it always results in death.

return to top of page