AV nodal reentrant tachycardia (AVNRT) is the most common form of SVT. In this condition, an extra pathway exists in or next to the AV node. If an electrical impulse enters this pathway, it may start traveling in a circular pattern. This may cause the heart to contract with each cycle, and may result in a very rapid, irregular heartbeat. Wolff-Parkinson-White (WPW) Syndrome
In WPW, an abnormal "bridge" of tissue connects the atria and ventricles. This extra pathway, called an accessory pathway, makes is possible for electrical
impulses to travel from the atria to the ventricles without going through the AV node. In people with WPW, an arrhythmia can get started when an impulse travels down the AV node to the ventricles, and then up through the accessory pathway to the atria. If the impulse continues to travel in a circular pattern, it may cause the heart to contract with each cycle and may result in a very rapid heartbeat. Because it is prone to
conduct impulses rapidly, an accessory pathway may also allow extremely rapid, and potentially serious, rhythms to occur. Atrial Fibrillation
In atrial fibrillation, multiple sites in the atria fire
impulses in uncoordinated fashion. As a result, the atria beat very quickly and ineffectively. The AV node, which acts as a "relay station," allows only some of the impulses to travel down the electrical system
and stimulate the ventricles. As a result, the heart rhythm is irregular, erratic, and usually (but not always) rapid. Atrial fibrillation may occur once in a while, or it may be long-standing (chronic). Preparing for the EP Study
Unless you are already hospitalized, you'll probably be admitted to the hospital for the study. In some cases, you may undergo the procedure at the hospital as an outpatient.
Several routine lab tests will be performed, including an ECG and blood tests. (Blood tests may be done one or two days ahead of the study.) The doctor performing the procedure will review your medical history and
examine you. (You may be seen by the doctor at the office several days before the procedure.) The doctor will explain the procedure, its purpose, potential benefits and possible risks. This is a good time to ask questions and, most importantly, to share any feelings or concerns you may have about the EP study. You will then be asked to sign a consent form. A nurse will shave and cleanse the area where the catheters
will be inserted. In most cases this will be the groin; in some cases, the arm or neck area. Shaving and cleansing makes it easier to insert the catheters and helps to avoid infection. A small intravenous needle ("IV line") will be inserted into a vein in your arm. It allows drugs to be injected directly into the vein, if necessary. You may also be given a sedative to help you relax. Before Your EP Study
Get specific instructions about the food you can have. Generally, you will be asked not to eat or drink anything for 6 to 8 hours before the procedure. (You may have sips of water
to swallow your medications.) Make arrangements with a family member or friend to drive you to the hospital. <BACK CONTINUED>
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