1. The Heart's Electrical System ES
2. The Diagnostic Electrophysiology Study [EPS] DS
3. What is an Ablation? Abl
4. Back to Education Main Page Edu
The Heart's Electrical System
To understand what an electrophysiology study is and how it is done, you first need a little background knowledge about the heart. The heart is divided by muscle and fibrous tissue into a right and left side. Each side has an upper chamber or atrium that collects blood returning to the heart and a muscular lower chamber or ventricle that pumps that blood away from the heart. The right atrium (RA) receives blood from you body and pumps it into the right ventricle (RV). The right ventricle then pumps it to your lungs. From the lungs, blood returns to your left atrium (LA) and then pumped into the left ventricle (LV). From the left ventricle it is pumped out to your body.
To make sure that the different parts of the heart work together and pump the blood with the right timing and sequence, the heart has an important built-in "electrical system". Think of it as a set of nerves or wires that run throughout the heart connecting all the parts. In the right atrium you will find the SA node – the "pacemaker" of the heart. It sends electrical impulses just like a spark plug in a car. The SA node therefore sets your heart rate. This impulse spreads throughout the atria like ripples in a pond, and then travels down to what we call the AV node. The AV node is similar to a wire cable connecting the atria and the ventricles and is responsible for sending electrical impulses from the atria to the ventricles. It splits into 2 branches called the right and left bundle branch which allows the even spread of the electrical signal to both ventricles simultaneously.
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The Diagnostic Electrophysiology Study
This section was written by the staff of the Arrhythmia Service in an effort to provide you with information about an "EP" (which is short for Electrophysiology), study is, how it is performed and other related information.
As you may already know from reading elsewhere at this website, the heart produces electrical signals that spread through the heart muscle to make the muscle contract. These signals are small but can be picked up on an electrocardiograph machine (see electrocardiogram). The electrocardiogram (EKG) is helpful but often the signals doctors need to see so small that they cannot be seen on an EKG or are hidden. An electrophysiology study (EPS) is a diagnostic test that allows your cardiologist to look at these heart signals in more detail and determine if you have an abnormality of your heart beat (otherwise called a cardiac arrhythmia), and where the problem lies. For a more detailed description of various arrhythmias, see sections below. An EP study is done to diagnose the source of your problem before a catheter ablation (see below) is performed. While an EP study may superficially resemble a heart catheterization or angiogram procedure, there is no real similarity.
The EP laboratory room looks a lot like a cardiac catheterization room in that there is a large X-ray machine present along with many computer screens and other medical equipment that are needed to keep you safe (see figure below). During the procedure, there will be 1 or 2 nurses along with one technologist and 1-3 doctors in the room. The nurse or technician will escort you into the room and help you onto the X-ray table. They will then connect you up to a automatic blood pressure cuff and a machine that continuously monitors your oxygen level. You will already be wearing a hospital gown which the nurses will lower so they can attach electrodes to the skin on your chest and shoulders. They will then apply 3 large sticky pads to your body - one of the front and another on the back of the chest and a third on the back of your thigh. Once these are all connected, the nurses may give you some sedating medication through your intravenous line to help you relax. In many cases, the drugs will make you fall asleep for much of the procedure. In other cases where an anesthesiologist is present, he or she will give you the drugs you need to keep you relaxed. The nurse will cover you with a warm blanket and expose the right groin and left shoulder. If necessary, they will shave the areas a bit more to keep it clean of hair.
The physician will clean the right groin and left shoulder areas and then place a large drape over your chest, abdomen and legs to keep the cleaned areas and equipment sterile. The doctor will then inject some local anesthetic (similar to dental freezing) and allow the areas to become numb. You should not feel any discomfort after the local freezing takes effect so please let the nurse or doctor know if you feel pain. The physician will use a needle to enter the veins that run past the groin and left shoulder and thread small wires (see figure below, left) up to the heart using a small amount of X-ray to guide their placement in the proper locations in the heart(figure below, right). These soft wires are used to pace your heart at different speeds and record electrical signals from inside your heart and are soft so that they usually do not cause any damage to the heart.
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Recordings and measurements will help the doctors determine the cause and location of your heart rhythm problem. If necessary, the doctors may give you one or more drugs through the intravenous line to help determine the type of problem you have. Once the measurements are complete, doctors may decide whether any treatments such as drugs or catheter ablation procedure (if you have consented). Otherwise, the doctors will remove the wires and put pressure on the areas where the veins were punctured so that a firm blood clot can form and seal the puncture holes. Small bandages will be put on these two area. The little cuts in the skin where the vein are punctured are very small and do not leave any significant scarring. If a catheter ablation procedure is warranted by the EP study findings and prior informed consent was obtained, the physicians would leave most of the catheters in place, insert the ablation catheter and proceed with the catheter ablation procedure (see below).
You will then be transferred to a stretcher and taken to a room to recover. We ask you not to raise your head off the bed and not coughing too vigorously for the next two hours because bleeding from these vein puncture sites can start up again . Your doctor will likely talk to your family about the test results first. When the sedation has worn off, the physician will talk to you and your family to make sure you are aware of the findings from the EP study.
Risks of the test procedure: No test procedure, especially one that involves the heart, is ever100% safe but an EP study is associated with a low rate of complications of approximately 1% or less. You should expect a small amount of bruising at the site where the veins are punctured. Very mild pain at these sites is normal for several days after the procedure and usually disappears after several days. Because the leg (femoral) artery is located next to the vein, puncture of the artery can occur. This rarely causes any permanent damage to the artery but serious injury to the artery can occur with resulting blockage of blood flow in the leg. This would require a surgical procedure to repair but is fortunately a rare occurence. In puncturing the vein in the left shoulder, the needle passes by the lung and can scratch it. This may cause a leak of air and the lung to collapse. A partial collapse may be sufficiently small that nothing more than close observation for a day or two is required. If the lung collapse is large, a chest physician specialist may be called in to insert a small needle into the chest to drain the air and re-expand the lung and your stay in hospital may be extended by several days until the problem is largely resolved. Although the thin wires used to record signals from your heart are soft, it is possible for one of these wires to poke through the wall of heart muscle (perforation), especially in the elderly patient. This can cause some chest or right shoulder pain at the time but usually resolves when the wire is pulled back. Rarely, muscle perforation can cause bleeding around the heart wall that impairs the heart's ability to pump effectively and requires a surgical procedure to drain the blood and close the small hole in the heart wall.
An explanation of the risks of the electrophysiology study will be provided during your visit prior to the procedure. Feel free to ask any questions you may have concerning the procedure or its' risks at that timed.
