Abnormal Heart Rhythms

What is an arrhythmia?

An arrhythmia (also called dysrhythmia) is an irregular or abnormal heartbeat.

What are the types of arrhythmias?

• Tachycardia: A fast heart rhythm with a rate of more than 100 beats per minute.
• Bradycardia: A slow heart rhythm with a rate below 60 beats per minute.
• Supraventricular arrhythmias: Arrhythmias that begin in the atria (the heart’s upper chambers). “Supra” means above; “ventricular” refers to the lower chambers of the heart, or ventricles.
• Ventricular arrhythmias: Arrhythmias that begin in the ventricles (the heart’s lower chambers.
• Bradyarrhythmias: Slow heart rhythms that may be caused by disease in the heart’s conduction system, such as the sinoatrial (SA) node, atrioventricular (AV) node or HIS-Purkinje network (see “The Heart’s Electrical System” section on the next page).

What causes arrhythmias?

Arrhythmias can be caused by:

• Coronary artery disease
• High blood pressure
• Changes in the heart muscle (cardiomyopathy)
• Valve disorders
• Electrolyte imbalances in the blood, such as sodium or potassium
• Injury from a heart attack
• The healing process after heart surgery
• Other medical conditions

Heart Rhythms on ECG

The heart’s electrical system triggers the heartbeat. Each beat of the heart is represented on the electrocardiogram (EKG or ECG) by a wave arm.

Normal Heart Rhythm 
The normal heart rhythm (normal sinus rhythm) shows the electrical activity in the heart is following the normal pathway. The rhythm is regular and the node is normal (about 50 to 100 beats per minute).

Tachycardia: fast heart rhythm (greater than 100 beats per minute)

Bradycardia: slow heart rhythm (less than 60 beats per minute)