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The normal rhythm of the heart is a tightly regulated but dynamic phenomenon that changes according to the metabolic needs of the body. The heart has built-in pacemakers and "wiring" that coordinate contractions in the organ's upper chambers (the atria) and lower chambers (the ventricles).
First, the electrical signal from the heart's master pacemaker, the sinoatrial (SA) node located in the atria, travels to the part of the heart that connects the atria with the ventricles, reaching another natural pacemaker known as the atroventricular (AV) node. From the AV node, the electrical signal travels down a structure called the bundle of His (sometimes referred to as the AV bundle); this is the first part of the heart's "wiring" system that conducts electrical activity into the ventricles.
The bundle of His enters the intraventricular septum (the wall between the heart's chambers), where it subdivides into the wire-like structures called bundle branches that carry the electrical impulse to Purkinje fibers, thin filaments that continue distributing the electrical signal to the ventricles' cells. This causes the heart to contract, pumping oxygen and nutrient-rich blood into the arteries and moving it throughout the body.
But what happens if there is a glitch in the heart's complicated "wiring" system causing it to "misfire"? The result can be an abnormal heart rhythm, an arrhythmia.
Most heart rhythm disturbances are transitory and nothing to worry about. For example, everyone has felt their heart "skip" a beat or two and speed up in times of fear or excitement or during exercise. And too much caffeine and certain medications can cause heart palpitations in some people. But arrhythmias, especially those that are frequent or chronic, can be serious — and some are life threatening. The consequences of arrhythmias usually depends not only on symptoms they can cause (such as faintness) but also on the presence of important abnormal structural conditions of the heart and/or heart disease.
| Common arrhythmias include: |
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Atrial fibrillation — A rapid, irregular heart rhythm originating in the atria that can cause symptoms such as palpitations, rapid heart beat, chest discomfort, shortness of breath and dizziness. In some individuals, atrial fibrillation increases the risk of stroke. |
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Ventricular fibrillation — This arrhythmia originates in the pumping chambers, or ventricles, and usually occurs in people who have a damaged heart, frequently the result of a heart attack. Because ventricular fibrillation is so rapid and is occurring in a damaged heart, the heart may not function properly or efficiently and this arrhythmia can be fatal. |
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AV Node Reentry Tachycardia — This rapid heart rhythm is the most common form of paroxysmal supraventricular tachycardia or PSVT. Patients with this arrhythmia do not have structural problems with their heart but have two pathways that can channel impulses to and from the AV node. Under certain conditions, usually following a premature beat, these pathways can form an electrical circuit starts a rapid (over 100 beats per minute) heart rhythm. |
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Wolffe-Parkinson-White Syndrome — This arrhythmia is caused by an extra electrical pathway from the atria to the ventricles. Although some people with WPW do not have any symptoms, others include experience palpitations, dizziness, and chest discomfort. Rarely, WPW can be life threatening. |
Treatments (and in many cases cures) are now available for many heart rhythm problems. Emory Heart & Vascular Center electrophysiologists at Emory University Hospital and the Carlyle Fraser Heart Center at Emory Crawford Long Hospital are experts at diagnosing and treating heart arrhythmias.
For more information, call Emory HealthConnectionSM at 404-778-7777.
Diagnosing Arrhythmias »
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