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 - Northwestern Memorial Hospital - Chicago

Arrhythmia Overview

When the conduction system follows a standard path in the heart at a "normal" rate, the heart rhythm is referred to as normal sinus rhythm. An arrhythmia is any variation from the normal rate and/or rhythm of the heartbeat.

Minor variation in the heart rate is usually normal. However, extreme and prolonged changes in heart rate are abnormal and can cause symptoms. The normal heart rate is usually between 60 and 100 beats per minute. A faster than normal heart rate is referred to as a "tachycardia," while a slower than normal heart rate is referred to as a "bradycardia." Much lower rates may be normal in young adults, particularly those who are physically fit.

Symptoms of Bradycardia (slow heartbeat)

  • Weakness and fatigue (feeling very tired)
  • Dizziness
  • Lightheadedness
  • Syncope (fainting spells)

Symptoms of Tachycardia (fast heartbeat)

  • Heart palpitations
  • Pounding in the chest
  • Chest discomfort
  • Dizziness
  • Lightheadedness
  • Syncope (fainting spells)

Variation in the heart rhythm is not normal. The heart rhythm is considered abnormal when the electrical impulses of the conduction system travel in abnormal pathways.

Patients experiencing a change in heart rate or rhythm may describe feeling a pounding in the chest, skipped or stopped beats, or a racing heartbeat. Collectively these symptoms are referred to as palpitations. Palpitations are an unusual awareness of the heartbeat and can occur with heart disease as in the case of some arrhythmias or without heart disease as in the case of extreme stress. Palpitations should be considered as potentially serious if they are associated with dizziness or fainting.

Arrhythmias can result from a variety of causes. Some arrhythmias may occur from an underlying heart problem (such as coronary artery disease, heart valve disease, or heart failure), thyroid dysfunction, or an electrolyte abnormality (e.g., a potassium, magnesium, or calcium imbalance). Other arrhythmias may occur in persons with or without an underlying disease from stimulants such as caffeine, emotional stress, from prescribed as well as illicit drugs, or physical activity.


For more information regarding the Bluhm Cardiovascular Institute please call 1-866-662-8467 or request a first time appointment online.

Last UpdateMarch 16, 2011