Index
Ep Defined | Getting Started | Working in the EP Lab
Right Atrium | Right Ventricle | Left Atrium | Left Ventricule | Cardiac Conduction | Cardiac Cell Properties | Action Potential | Sympathetic or Not | Med Page
Electrograms Defined | Recording Modes | Electrode Spacing | Filters | EGM Interpretation | Arrhythmia Analysis
The Physical Lab | Tools of the Trade
Setting Up | Catheter Placement | Baseline Measurement | SNRT | Conduction Study | Arrhythmia Induction | Pacing Protocols | Ablation | Tilt Table | Secrets to Success
Bradycardia | Atrial Tach | Atrial Flutter | Atrial Fibrillation | AVNRT | AVRT | Ventricular Tachycardia
Surface ECG's | Intracardiac Questions | Med Challenge | Advanced

Introduction to EP

A Trial by Fire....

          If you asked 100 different people who work in EP about their initial lab experience, you would find that most of these stories bear a striking similarity to each other. The field of EP is one that, even today, has little to offer in the way of education. For this reason, most people learn about EP from on the job training. Because of the complexity of this field, an "on the job" training approach presents a significant challenge to those who attempt it. In most cases, the intrepid adventurer who starts working in the field of EP is completely unaware of what they have gotten themselves into. Even those who feel that they understand EP because of previous experience with devices such as pacemakers or ICD's will usually find that they have entered into a strange and unknown realm. An even greater challenge awaits those who are recruited from a cardiac cath lab to start working in an EP program. With little warning, these people are yanked from the simple straightforward realm of the heart caths and stents and plunged into the strange world of electrograms, multi-electrode arrays, mid diastolic potentials and isochronal maps.

          To the casual observer, it is easy to believe that people who work in the cardiac cath lab are qualified to switch over to EP. At first glance, the similarities between these procedures seem to suggest that this transition should be an easy one. Both procedures introduce catheters into the heart by way of either the venous or arterial vasculature. Both fields have similar staffing requirements, one person to assist the physician, a second staff member who is responsible for patient care and a third person who monitors and records information pertinent to the procedure. The equipment used in both areas is also very similar. Fluoroscopy is used in both. ECG and blood pressure monitoring is standard to each of these procedure groups. Thus, it seems, that it should be easy for those who work in the cath lab to transition over to EP. This however, is rarely the case.

          Invasive diagnostic and interventional cardiology procedures that focus on the vasculature are fundamentally and procedurally different from those that are applied to the conduction system. A diagnostic heart cath is fairly straight forward. You place a catheter at the ostium of the artery you wish to visualize, inject some contrast and look for narrowed areas. If you find any, you decide on the best form of intervention. In a diagnostic EP study, things are not so straight forward. The basic approach is the same in that you place one or more catheters in the region of interest and you look at the signals. The difficulty lies in the fact that identifying what is normal and abnormal requires the user to, in essence, learn a whole new language. This new language, at first, seems somewhat similar. Many terms used in EP are familiar to those who work in the cath lab or even with devices. Terms like electrograms, arrhythmia, unipolar, bipolar, SVT and VT all have familiar overtones to them. But as the neophyte ventures further into the realm of EP, these terms begin to take on deeper, more complex meanings.

          The surface ECG's we looked at during the heart cath begin to take on greater importance and deeper meaning. Suddenly the size and shape of the P wave has meanings we never understood before. Our familiar 12 lead is augmented by a whole new type of electrogram, the intracardiac EGM. Unipolar and bipolar take on meanings we never considered before. QS configuration denotes early activation. Concealed R waves suggest far field or epicardial activation. Fractioned electrograms denote conduction barriers. Early electrograms are targets for ablation. Early meets late in reentry is dependant upon the location of the reference. The terminology is familiar, yet the meaning is elusive. There are also new terms to understand, drivers, rotors, short radial reentry, macro reentry, concealed entrainment, and the list goes on.

          This is where so many of us started in EP, in a place that is somewhat familiar yet completely unknown. The seasoned cath lab vet has suddenly become the bumbling junior flunky. Terminology such as SVT or VT that was used to classify arrhythmias is no longer considered adequate when describing abnormal rhythms. In this new language, supraventricular tachycardias are broken down into more descriptive categories such as focal or reentry arrhythmias. Rhythms such as atrial flutter that once seemed simple and straight forward take on vastly more complex definitions. Is the flutter right atrial or left atrial? Is it clockwise or counterclockwise? Is it isthmus dependant or substrate dependant? Accessory pathways are no longer just WPW. Sometimes they are concealed. Atrial tach's become crista tach's or vein of marshal tach's. Sinus tach can be either appropriate or inappropriate. It just keeps getting stranger and stranger.

          Even things that at one point seemed very black and white have suddenly been clouded in shades of grey. When the patient in the cardiac cath lab goes into ventricular tachycardia, there is an immediate response from all staff members. Everyone in the room becomes focused on one singular goal, to get the patient out of VT as fast as humanly possible. When a patient goes into VT during an EP study, the response is strangely different. The patient is quickly assessed. If they remain conscious, the work continues. Recordings are made, 12 leads are analyzed, catheters are moved around to different regions of the ventricle to collect information. The patient may be allowed to remain in VT for what seems to be an eternity to someone who is unfamiliar with EP. Pacing maneuvers may be utilized to "entrain" the arrhythmia. During this time, the patient is closely monitored under the watchful eyes of the EP lab staff. When the information is collected or when the patient no longer can tolerate being in VT, steps are then taken to terminate the abnormal rhythm. There is almost a surreal calm that pervades the lab during moments like this. For someone who is new to the lab, it is moments like these that most clearly emphasize the difference between cath and EP procedures.

          It is also in moments like this that the novice EP staff member may realize that they have found a new calling. For if you experience one of these strange events in the EP lab and find that you have a strong desire to understand more about what is really happening during these procedures, you may have taken the first step on a long and difficult road. For learning EP is not easy. There are no schools that teach EP. You can't just sign up for EP 101. The only way to learn cardiac electrophysiology is to go into the lab and do it. Go into the lab each and every day knowing that you are going to be lost and confused for the next several months. Ask questions, lot's of them. And don't be disappointed if the answers you get initially seem to elude your understanding. Take it one step at a time. Learning EP is truly “a trial by fire”.

          For some people, cardiac electrophysiology will be nothing more than an intense frustration and a severe headache. If you are one of these people, stop reading this now. EP is not for you. Do not feel bad. EP is not for everyone. If, however, you are one of those people who find that you have a strange compulsion to figure out this new language, then you are probably in the right place. This also means that there is a good chance you may be an EP Geek. Welcome to the club. Sit down, get comfortable and start taking notes. Your trial by fire has begun.

Updating the Lab...

          If you are a return visitor to the lab, you have probably noticed our new look. I originally wrote this web site when I first started in cardiac electrophysiology. Since that time, I have had the opportunity to take part in EP procedures in labs across the country.  My schedule, needless to say, has been a bit hectic. Now I am working in EP education, time is more flexible and I have learned so much more than I knew before. And thus, I begin the process of updating this page with the hopes that, when I am finished, it will be the educational resource I have always intended it to be.

          So read on and enjoy!! If you have any suggestions as to what you wish to see here, please let me know!! I can be reached by clicking here.

 
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