Causes
- Normally, the heart's most rapidly firing cells are in the sinus (or sinoatrial or SA) node, making that area a natural pacemaker.
- Under some conditions almost all heart tissue can start an impulse of the type that can generate a heartbeat. Cells in the heart's conduction system can fire automatically and start electrical activity. This activity can interrupt the normal order of the heart's pumping activity.
- Secondary pacemakers elsewhere in the heart provide a "back-up" rhythm when the sinus node doesn't work properly or when impulses are blocked somewhere in the conduction system.
An arrhythmia occurs when:
- The heart's natural pacemaker develops an abnormal rate or rhythm.
- The normal conduction pathway is interrupted.
- Another part of the heart takes over as pacemaker.
Symptoms
Arrhythmias can produce a broad range of symptoms, from barely perceptible to cardiovascular collapse and death.
- A single premature beat may be felt as a "palpitation" or "skipped beat."
- Premature beats that occur often or in rapid succession may cause a greater awareness of heart palpitations or a "fluttering" sensation in the chest or neck.
When arrhythmias last long enough to affect how well the heart works, more serious symptoms may develop:
- Fatigue
- Dizziness
- Lightheadedness
- Fainting or near-fainting spells
- Rapid heartbeat or pounding
- Shortness of breath
- Chest pain
- In extreme cases, collapse and sudden cardiac arrest
This content is reviewed regularly. Last updated 01/15/09.
