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Common Cardiac Arrhythmias

Mar 23, 2010 | By Tina M. St. John, M.D.
Common Cardiac Arrhythmias
Photo Credit stethoscope lying on a ekg image by Joseph Dudash from Fotolia.com

The heart normally beats in a rotating cycle of contraction and relaxation. This elegantly coordinated action is controlled by electrical impulses, which normally move across the heart with precision and reliability. When something goes awry with the electrical conduction system of the heart, its normal rhythm is disrupted---a condition known as cardiac arrhythmia. The heart may beat too slowly, too rapidly, or irregularly. Different types of cardiac arrhythmias are distinguished by the source of the problem and the resulting cardiac rhythm.

Premature Beats

Premature beats are the most common type of cardiac arrhythmia. Dr. Douglas Zipes of the Krannert Institute of Cardiology has described cardiac arrhythmias as heart hiccups, a description that is particularly apropos to premature beats. This arrhythmia occurs when an errant electrical impulse is discharged resulting in a feeling of either a missed heartbeat or an extra beat. This type of arrhythmia is usually episodic and of no consequence. Stress, caffeine, alcohol and smoking may bring on episodes of premature beats.

Atrial Fibrillation

Atrial fibrillation (also known as A-fib) is the most common, potentially problematic cardiac arrhythmia. An estimated 3 percent to 5 percent of Americans have atrial fibrillation, according to the American College of Cardiology, with older persons most commonly affected. This arrhythmia is characterized by rapid and disorganized electrical impulses in the upper chambers of the heart that cause them to quiver rather than contract in a coordinated fashion. During an episode of atrial fibrillation, the impulses in the upper heart chambers (the atria) are firing at a rate of 300 to 600 per minute. During an episode, there may be a feeling of fluttering, racing or pounding in the chest.

Atrial Flutter

Atrial flutter is similar to atrial fibrillation but with a somewhat slower and more regular atrial rate, typically 250 to 350 per minute. Atrial flutter may progress to atrial fibrillation.

Paroxysmal Supraventricular Tachycardia

Paroxysmal supraventricular tachycardia (PSVT) is a rapid, regular heart rhythm that originates in the upper chambers of the heart. This rhythm is usually episodic, beginning and ending abruptly. The heart rate is typically between 160 and 240 beats per minute during an episode. PSVT most commonly presents in young to middle-aged adults. Symptoms of lightheadedness, chest discomfort and shortness of breath may occur during attacks.

Bradycardia

Bradycardia is an abnormally slow heart rate, typically less than 60 beats per minute. This arrhythmia is caused by disease or malfunction in one or more parts of the heart's electrical conduction system. Symptoms may include fatigue, lightheadedness, dizziness and fainting.

Ventricular Tachycardia

Ventricular tachycardia (also known as V-tach) is an abnormally rapid heart rate that originates in the lower chambers of the heart (the ventricles). During V-tach, the ventricles are attempting to contract at a rate of more than 100 per minute. However, blood cannot be effectively pumped to the body at such a high ventricular rate. Dizziness, fainting, and shortness of breath are common symptoms. Restoration of a normal heart rhythm is critical as cardiovascular collapse and death may occur.

Ventricular Fibrillation

Ventricular fibrillation (also known as V-fib) is a medical emergency. Electrical impulses originating in the ventricles fire in a rapid, erratic manner leaving the ventricles quivering and unable to effectively contract. V-tach may progress to V-fib, especially in people with underlying heart disease. Cardiopulmonary resuscitation (CPR) and defibrillation are urgent as brain and heart damage begin within minutes of the onset of V-fib. Death can occur quickly if a more normal cardiac rhythm is not reestablished.

References

Article reviewed by M.J. Ingram Last updated on: Mar 23, 2010

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