I Can See Your Heart Beat: A Patient’s Guide to the Heart’s Electrical System

EP Lab Digest

EP Lab Digest

Jeff Schoeben, RCIS, a past contributor to EP Lab Digest®, has recently written and published a patient guide to heart arrhythmias, entitled I Can See Your Heart Beat: A Patient’s Guide to the Heart’s Electrical System. Featured here is an excerpt of chapter 5.

Chapter 5: The Electrophysiology Study

In this chapter, I will explain to you why your electrophysiologist recommended the study for you and what to expect when you enter the procedure room.

First, let me describe an EP study. An electrophysiology study is a procedure to recreate the symptoms you are experiencing, but in a controlled situation. The staff, which is comprised of your doctor and a combination of cardiovascular technologists, x-ray technologists, respiratory therapy technologists, and nurses will use electrode catheters in various areas of your heart to compare your electrical signals to what are considered normal electrical signal values. Then pacing protocols will be used to recreate your symptoms or document your arrhythmia.

There are many ways you may have qualified for an EP study. Strict regulations were adopted in the United States and worldwide medical communities who need EP studies. Some of these include information from a Holter or King of Hearts monitor, information from an implantable loop recorder, unexplained syncope, or something documented during a visit to your physician or in an emergency room. Once you meet any of these criteria, you will be scheduled for the EP study, if you are in agreement that this is reasonable. If you are an outpatient, not already registered in the hospital, you will be directed to admitting first, and then the outpatient unit, where all the preoperative orders will be completed. If you are already a patient in the hospital, these orders will be carried out in your room.

Once your doctor and the electrophysiology staff are ready to perform your procedure, a representative from the lab will contact your unit or floor for “pre-op.” This is your chance to use the restroom right before you go into the procedure room or laboratory. The procedure may take from one to eight hours, depending on what is found during the EP study. If a radiofrequency ablation, pacemaker, or implantable cardiac defibrillator is indicated, your time in the lab will be longer than if a negative result occurs, in other words no arrhythmias noted. The above-mentioned procedures will be discussed in later chapters.

In my experience, a typical EP study will take from one to two hours; however, depending upon the findings, the procedure time can be longer. This is why I mentioned earlier that if you are not the first case scheduled in the procedure room, your scheduled time is only an estimate. Please be patient, as your doctor and staff work diligently to ensure that each patient receives the proper intervention needed to achieve the result you and your doctor desire.

When it is time for your procedure, a member of the staff from the lab or hospital transport department will arrive at your room and take you to the lab, either by stretcher or wheelchair. As you enter the room, you will see a lot of equipment. You will notice that the room is chilly. The temperature in these rooms is kept lower to keep the millions of dollars worth of equipment from overheating. To compensate for the lower temperatures, a lab staff member usually has access to a warm blanket, so do not be shy about asking for one.

Let us take a moment and examine the equipment you will see. There are usually three stations used in an EP study: a recording station, a circulator station, and the procedure station. Each station has different equipment that when used all together allows the doctor and staff to complete your procedure in the safest and most efficient manner. At this point, let me explain the equipment you see in the room pictures provided.

At the recording station, (Figure 10), you will see screens for the recording system. One of these screens is used to view live electrical signals, and the other is a review screen, where the recording person can freeze images from the live screen for the doctor to review. Another piece of equipment at the recording station is the stimulator. When connected to the catheters the doctor places in your heart, the stimulator will allow for pacing at rates higher than your normal heart rate. The stimulator is a vital piece of equipment, which uses a wide range of heart rates to narrow down the specific electrical timing that initiates your arrhythmia. A third screen allows the recorder to view x-ray images of the catheter placements.

Another piece of equipment is the ablation generator. I will discuss the use of an ablation generator at a later point.

The circulator is your contact person during the procedure. This staff member is responsible for monitoring your vital signs: heart rate, oxygen saturation, and blood pressure, administering medications, scratching your nose (if requested), and implementing rescue therapies if needed. This station (Figure 11) has access to the live screen via a “slave” monitor, a drug-dispensing machine, and two defibrillators.

The first defibrillator is usually connected to your chest and back by patches before the procedure, and the second is equipped with paddles in case the patches are unsuccessful. Also located at this station is an oxygen meter where extra oxygen is administered according to your level of consciousness.

The procedure station (Figure 12) has a hard, flat, narrow table with a thin mattress, an x-ray unit commonly called a C-arm for its shape, catheter connector modules, and a 12-lead EKG cable. Also situated at this station is a blood pressure cuff and pulse oximeter, which measures your heart rate and oxygen saturation. In addition, a separate table with all the equipment needed for the procedure will be on either side of the procedure table.

As you view these three stations, a staff member will help you onto the procedure table from your stretcher or wheelchair. Once you are positioned on the table, the staff will prepare you for the procedure. He/she will give you arm boards, which allow you to keep your arms comfortably at your sides. At this point, the staff member may or may not put soft bracelets on your wrists. These are tied to the table and help refrain you from putting your hands into the sterile work area. Before tying these to the table, the rescue patches will be applied — one to the front of you and the other to your back. Next, one of the staff members will hook up the 12-lead EKG using smaller patches. After all of the wires are attached, a staff member will expose your groin area and place a towel over your genitalia, while leaving access for sheath placement. These areas will be washed with an antiseptic solution to prevent an infection. In addition, the circulator will place oxygen tubing in your nose to regulate supplemental oxygen to your level of consciousness throughout the procedure.

After the above preparation is complete, a staff member will inform the doctor you are ready for the procedure. At this point, the doctor will enter the procedure room to identify you as the patient and confirm with the staff what procedure is being performed. This is also your last chance to have any questions answered before the procedure begins. During this time, the scrub, (doctor’s assistant) will put protective lead apron on, as well as a hat and mask, before performing a sterile scrub and entering the room. Here, the scrub will don a sterile gown and gloves and then place a sterile drape over you, leaving the previously cleaned areas exposed for sheath placement. The circulator will then administer relaxing medications ordered by your doctor, and the doctor will be completing the sterile scrub. Following the sterile scrub, your doctor will put on a sterile gown and gloves and enter the room.

Once all the sterile preparation is completed and you are comfortably sedated, the doctor will begin by numbing the groin areas with an agent comparable to novacaine used in a dentist’s office. After giving the numbing agent ample time to work, the doctor will place sheaths in your groin. A sheath is like an IV, only larger being from 1–4 mm in diameter. It has a one-way valve so a variety of catheters can be placed through it with minimal or no blood loss. The number of sheaths (one to four) depends on which arrhythmia the doctor is trying to identify. The sheaths are put in place by inserting a needle into the vein, and a guide wire through the needle. The needle is then removed and the sheath is placed over the wire. With the wire removed and the sheaths in place, electrode catheters are guided into position in the heart. In a typical three-catheter study, one catheter will be placed in the high right atrium to record signals from the upper chamber of the heart; a second catheter is placed across the His (pronounced, “hiss”) bundle (the junction box), to record signals from the low right atrium, through the His bundle, to the upper right ventricle; and a third catheter is placed in the right ventricular apex (the lower chamber). When proper catheter placement has been confirmed, a gathering of information can begin.

The doctor will move from your bedside to the recording station. Your basic electrical measurements will be taken and compared to normal values. If any of these values are out of normal range, they provide one piece of information for a diagnosis. Once the basic measurements are complete, the doctor will begin programmed stimulation. It is important for you to understand that your arrhythmia is initiated by a certain glitch in your electrical system, and the stimulation protocol is used to find the exact timing of this glitch. A generally accepted protocol uses an eight-beat pacing train at 100, 120, and 150 beats per minute and adding one, two, or three early beats. These are used in both the upper and lower chambers of the heart. If the arrhythmia the doctor is trying to recreate is from the lower chamber and pacing from the tip of the lower chamber is negative, the catheter will be moved to a second position. If pacing from both of these sites produces no results, the chance of having a ventricular arrhythmia after you leave the lab is very low. On the other hand, if the doctor is trying to reproduce an atrial arrhythmia and the pacing protocol did not initiate one, the doctor may have the circulator start an IV medication to increase your heart rate. Once your heart rate reaches the goal determined by the doctor, the protocol will be repeated. Again, if the result is negative, there is a very low chance of an atrial arrhythmia occurring after leaving the lab.

It should be duly noted that the description I have given for an electrophysiology study could be modified if there is some documentation that the arrhythmia is present. A limited study may be performed if a cardiac arrest brought you to the hospital. In this situation, the doctor may do only a ventricular pacing protocol to see if ventricular tachycardia can be induced, and if it can, does it deteriorate to ventricular fibrillation? This information can be used when programming an implantable cardiac defibrillator, as discussed in a later chapter.

Now, what if your study was positive? In the event that an atrial arrhythmia was induced, the doctor may opt to use radiofrequency ablation as a curative procedure. This will depend upon the arrhythmia and the capability of the lab to perform such a procedure. In some cases, the atrial arrhythmia will be one that is seen infrequently, and may have a greater chance of success in a university lab where they see that particular rhythm almost daily. Your doctor wants to give you the greatest opportunity for success and in certain situations may suggest this option. Most atrial arrhythmias, however, may be cured by your doctor in the same setting as your EP study.

If your EP study was negative, the catheters will be removed, as well as the sterile drapes, and then a scrub person will remove the sheaths and apply pressure until any bleeding ceases. Finally, you will be returned to your room where you will lie in bed for the doctor-prescribed recovery period. Once this period is complete, you will be discharged to return home or to your hospital room.

If a radiofrequency ablation is recommended to cure your arrhythmia, a fourth sheath may be inserted to allow access of a coronary sinus catheter. This catheter enters the coronary sinus, which is the return pathway of blood from the heart to get more oxygen. A special ablation catheter will need to be used. These catheters are usually larger than those used during the diagnostic test; therefore, one of the sheaths may be exchanged for a larger sheath. Catheter-induced ablation, as described in Dorland’s Medical Dictionary, is delivery of destructive electrical energy, usually high energy or radiofrequency alternating current, via electrodes on a catheter. In simple terms, ablation blocks the abnormal electrical pathway and redirects the signal down the normal pathway, or eliminates an impulse coming from a single site.

The majority of arrhythmias fall into three categories: macro-reentrant tachycardia, micro-reentrant tachycardia, and focal tachycardia. A macro-reentrant tachycardia is a large-loop tachycardia, whereas a micro-reentrant tachycardia is a small-loop tachycardia. In contrast, a focal tachycardia starts from a single point outside the normal electrical system, but as it progresses, it jumps into the normal system, causing it to go much faster than normal.

If you ask any electrophysiologist which form of ablation is preferred, the answer will be radiofrequency ablation. Radiofrequency was preceded by DC (direct current) ablation, which was found to have some unacceptable outcomes. With the development of radiofrequency ablation, a safe and effective form of ablation has allowed thousands of patients to lead normal lives after their arrhythmias were completely eliminated. While radiofrequency is the standard for ablation, other forms are proving successful, such as cryogenic (freezing), ultrasound, microwave, and alcohol. Each of these forms of ablation seems to have a specific application at this moment, but may replace radiofrequency in the future.

In the following pages, I will describe each of the most prominent arrhythmias that lend themselves to ablation and how your doctor identifies your arrhythmia. These arrhythmias include AVNRT (atrioventricular nodal reentrant tachycardia); AFL (atrial flutter); AT (atrial tachycardia); concealed bypass tract, or WPW (Wolff-Parkinson-White syndrome); A-fib (atrial fibrillation); PVCs (premature ventricular complexes); and right ventricular outflow tachycardia.

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Reprinted with permission from Jeff Schoeben.