Irregular Heartbeat: Causes of Atrial Fibrillation

An EKG (electrocardiogram) can quickly detect an irregular heartbeat, so it is often used to diagnose atrial fibrillation and other heart conditions. A normal EKG reveals an atrial heart rate between 60 to 100 beats per minute. Electrical activity in the atrial chambers results in ventricular chamber contractions of 60 to 100 beats per minute as well.

 

An EKG showing an irregular heartbeat produced by atrial fibrillation is quite different. EKG results demonstrating atrial fibrillation reveal an atrial heart rate as high as 600 beats per minute. With this arrhythmia, the steady heartbeat of a normal EKG is replaced with beats of irregular frequency. The irregular electrical impulses in the atrial chambers affect the ventricles, which respond by beating up to 200 beats per minute.

EKG testing has shown that the irregular heartbeat that characterizes atrial fibrillation originates in the atrial chambers (the small, upper chambers of the heart). The electric signals in the atria become confused and erratic, leading to the rapid and irregular heartbeat seen on an EKG.

Cardiovascular diseases such as coronary artery disease, angina pectoris, and hypertension are the most common causes of an irregular heartbeat. Damage to the heart caused by a heart attack or the stress caused by angina may both result in atrial fibrillation. The relationship between heart disease and irregular heartbeat is complicated: while heart disease may cause atrial fibrillation, some heart conditions may be complications of an irregular heartbeat.

Thyroid hormone levels affect the functioning of the heart. Excessive levels of thyroid hormone (hyperthyroidism) have been linked to a rapid, irregular heartbeat. If thyroid hormone levels are an issue, controlling thyroid hormones may be the first choice for atrial fibrillation treatment.

A number of events can trigger an irregular heartbeat. Emotional stress is associated with several heart conditions. Stress can trigger both atrial fibrillation and angina pectoris. Given the negative effects of emotional stress on heart conditions, learning more about the relationship between stress and health is well advised.

In the absence of stress, an existing heart condition, or thyroid hormone imbalances, it may not be possible to identify the irregular heartbeat trigger. However, there are a few other causes of atrial fibrillation that should be considered. Fever may result in an irregular heartbeat, especially in the elderly. Recent heart surgery has also been known to trigger atrial fibrillation. Heavy use of alcohol, caffeine, and some illicit drugs may also result in an irregular heartbeat.

Resources

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Beers, M.H. & Berkow, R. (ed). Arrhythmias. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

Fauci, A., Braunwald, E., Isselbacher, K., Wilson, J., Martin, J., Kasper, D., Hauser, S. & Longo, D. (ed). Harrison's Principles of Internal Medicine, 14th Edition. McGraw-Hill, New York, 1998.

Mayo Foundation for Medical Research and Education. (updated 2005). Atrial fibrillation.

NASPE-Heart Rhythm Society. (nd). Atrial fibrillation and flutter.

National Library of Medicine. (updated 2004). Atrial fibrillation/flutter. MedlinePlus Medical Encyclopedia.