Different Types of Arrhythmias

What are the different types of arrhythmias?

There are many types of arrhythmias. 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 arising in the atria are called atrial or supraventricular arrhythmias. Ventricular arrhythmias begin in the ventricles. In general, ventricular arrhythmias caused by heart disease are the most serious.

Arrhythmia Types - Originating in the Atria

• Sinus arrhythmia

Normal cyclic changes in the heart rate during breathing. Common in children and often found in adults.

• Sinus tachycardia

The sinus node sends out electrical signals faster than usual, speeding up the heart rate. A heart rate greater than 100 beats per minute.

• Sick sinus syndrome

Sometimes the sinus node, as well as the AV node, doesn't work properly. Different combinations of supraventricular arrhythmias both slow and fast, are produced on an intermittent basis. This condition almost always indicates disease of multiple areas of the heart conduction system. Symptoms of sick sinus syndrome are caused by either too fast or slow heart rate and include near syncope or syncope (passing out due to not enough blood reaching the brain), chest pain, shortness of breath, palpitations and stroke.

Holter monitoring (a device continuously recording heart electrical activity for 1-2 days) is often needed to diagnose sick sinus syndrome. A routine EKG often does not show intermittent arrhythmias common in this syndrome.

Bradycardias causing symptoms usually require a pacemaker. Tachycardias are usually treated with medication to slow the heart rate down. Medications are usually started after pacemaker insertion because they can make bradycardias worse.

• Premature Atrial Contraction (PAC)

Irregular heart rhythms are most often caused by premature beats or extra beats. These originate in the upper chambers (premature atrial contraction, PAC). When we feel our heart "skip a beat," it usually results from this type of arrhythmia.

The heart does not skip a beat. Instead an extra beat comes sooner than normal. This is followed by a pause that causes the next beat to be more forceful. The person feels this more-forceful beat.

Premature beats are common in healthy people of all ages- most people have them at some time. Caffeine, alcohol, stress and fatigue may cause PAC's to occur more frequently. Usually no special treatment is needed and no cause can be found. The premature beats may disappear, and even if they continue, most people tolerate them well.

• Supraventricular tachycardia (SVT)
A series of early beats in the atria speed up the heart rate (the number of times a heart beats per minute). In paroxysmal tachycardia, repeated periods of very fast heartbeats begin and end suddenly.

The most common abnormal tachycardia in children (and common in adults as well) is reentrant supraventricular tachycardia (SVT). It's also known as paroxysmal atrial tachycardia (PAT) or paroxysmal supraventricular tachycardia (PSVT). The fast heart rate involves both the heart's upper and lower chambers. This isn't a lifethreatening problem for most people. For many, it doesn't require medical therapy. Treatment is considered if episodes are prolonged or frequent. There are several subgroups of SVT, including Wolf-Parkinson-White syndrome (WPW). The heart rate is generally between 160-200 beats per minute which can be tolerated by most people for an extended period of time.

• Wolff-Parkinson-White syndrome.

A specific type of SVT this condition is caused by abnormal pathways between the atria and ventricles, causing the electrical signal to arrive at the ventricles too soon and to be transmitted back into the atria. Very fast heart rates may develop as the electrical signal ricochets between the atria and ventricles. Sometimes the heart rate can be very high (200-300 beats per minute). Some medications used to slow regular SVT down can actually make the heart beat even faster in a particular type of WPW.

• Atrial flutter

Rapidly fired signals cause the muscles in the atria to contract quickly, leading to a very fast (250-350 atrial beats per minute) and regular heartbeat. There is normally a conduction block at the AV node. That is for any given number of atrial beats reaching the AV node a certain number are blocked. Usually one ventricular beat occurs for every two atrial impulses reaching the AV node. Sometimes 3:1 or even higher block occurs (that is for every three atrial impulses reaching the AV node one is conducted through to the ventricles).

Atrial flutter almost always occurs in patients with underlying heart disease. Atrial flutter is sometimes seen as a transition rhythm between atrial fibrillation and normal sinus rhythm.

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