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

Working in the EP Lab - Technically Speaking

The Tech Challenge...

       The one person that experiences the greatest degree of change in the transition from standard cath lab procedures to electrophysiology is the person chosen to operate the EP monitoring system. Whenever an electrophysiology program is started, one person is picked as the "guinea pig". This lucky soul gets placed on a chair in front of some strange looking equipment and told, "Don't worry. This will be easy". Nothing could be further from the truth.

          It is a strange form of culture shock that is experienced by the staff member who gets put in front of the EP monitors for the first time. I have talked with both nurses and techs who have experienced this cross over and the stories are amazingly similar. The confidence you once had vanishes into thin air and you suddenly become the stumbling rookie working your first case ever in the lab. Everything you knew before is thrown out the window and you have to learn a whole new set of rules. This is like being lost inside your own home. What was once familiar territory in the lab has suddenly changed and you are not sure what you are supposed to do. Instead of wanting to know if the pressure was phasic or what the gradient was, your doctor now wants to know if the AH has jumped or if 5-6 is earlier than 3-4!!! And here you are looking at a screen that instead of the familiar two surface ECG leads and one or two pressure channels, has four surface ECG leads, 6 or more intracardiac leads and is traveling across the screen at the nauseating speed of 100mm/sec. After a few minutes looking at the monitors and their high speed motion, your head begins to ache and you start to wonder what forces in life you have pissed off so badly that they would put you in a position like this.

          Eventually, you begin to understand what you are looking at and what you are supposed to be doing. Things become easier and comprehension slowly begins to grow. Then comes the day when you look at the signals zipping by on the screen and you suddenly see the left sided pathway without any help from the doctor. A light goes on inside your head and you begin to grasp the mystery of electrophysiology. At this point, you are either hooked and you want to learn more, or you have decided that you would rather have sharp objects painfully inserted into your body than have to sit in front of those monitors one more time. This is the way it is with EP, you either love it or you hate it.

The EP Lab

          For the technically oriented person, working in EP is a dream come true. There is a wide variety of neat gadgets and gizmo’s with electronic displays, flashing lights, moving waveforms and 3 dimensional maps with moving colors on them. What techno geek could ask for more? Starting before the first EP study even begins, the Tech’s adventure with all the new pieces of equipment begins. The old recording system with its 5 or 6 channels of information is replaced by the new more powerful version that can have over 100 channels. The temporary pacemaker has mutated into device capable of delivering complex pacing algorithms to any catheter in the heart at the click of a button.

          There are new catheters and sheaths with the strangest configurations. How many of you have held up the St. Jude SAFL sheath and wondered just how the heck that thing was supposed to work? The catheters are all like temporary pacing wires but with more electrodes. Some catheters have up to 64 electrodes that can both sense and pace. Then there are new pieces of equipment to get familiar with. There is the RF generator that delivers radio frequency energy to ablate the problematic cells that are the source of abnormal rhythms and the Cryo unit for those cases where freezing the cells is preferred. And it doesn’t stop there..

          Sooner or later, the cardiac mapping system will make its appearance. This is when the fun really starts. It is always fun to watch the expression on someone’s face the first time they see atrial flutter displayed as a dynamic map that shows both activation and voltage at the same time. The reaction is almost universal, “That is so cool!” Now the lab can map voltage, activation and fractionation on anatomically accurate representations of the cardiac structure. You can even import these structures from a CT or MRI! Man, it is like being a kid in a candy shop.

Cardiac Anatomy and Physiology

          While learning all the ins and outs of the variety of new toys the lab, something else begins to happen to the EP initiate. They find that their knowledge of the human heart is beginning to grow. It is almost impossible to prevent. Being exposed to so much information about the heart simply makes it easy to gain a better understanding of how it works. With very little effort, many Techs find that they are learning more and more about cardiac anatomy and physiology. This is the first step on the long road to mastering EP and it is a long road. So grab what information you can, go online and search the web, order some books and let the learning process begin.

EP Fundamentals

          It won’t take long in your learning process to come across the cardiac action potential. This is due to the important role it plays in electrophysiology. Everything we know about the electrical conduction system of the heart is directly related to the function of the cardiac action potential. This minute signal that occurs on the cellular level is pretty difficult to visualize directly. So instead, we look at the cumulative affect the action potential has on specific cardiac regions. By placing electrodes within a region of interest, the summation of all the action potentials within that region can be visualized together as an electrogram.

          If you look at a small region by placing electrodes close together, you will see an electrogram that reflects only the local activity. Depending upon how the electrodes are set up and how the signal is filtered, different types of information can be gained. When you spread the electrodes out to the point where they are on the skin, each on a different side of the heart, you see the global sum of all the action potentials as they happen. This is the surface electrocardiogram.

          The surface ECG is the oldest tool that EP has. It has been around for over a hundred years, and more papers have been written on it than on any other aspect of EP. Knowing how to read a 12 lead is a great tool to have in your arsenal. Many people who come into the field of cardiac electrophysiology already have a good understanding of the surface ECG. Those who do not yet posses that skill will have it soon enough. For reading electrograms, whether they are recorded from surface electrodes or from electrodes placed within the heart, is the key skill that you must have to succeed in EP.

EP Procedures

          While you are learning about the basics of electrograms, your time in the lab will also be exposing you to the different procedural aspects of cardiac electrophysiology. At this point in the development of the EP Tech, many different branches of EP knowledge will be learned together. The different procedures and testing protocols that are used in the lab will begin to make more sense as your knowledge or the heart continues to grow. This is a fun time in the lab and there is a great deal to learn.

          You will find that pacing is a key element of the EP study. You will also find that there are method of using pacing that you never even dreamt of! There are SNRT’s, Burst pacing, Ramp pacing, Overdrive pacing, Incremental pacing, pace entrainment, pace mapping and programmed stimulation. Using pacing, the Electrophysiologist can, in many instances, induce or terminate an arrhythmia. He can learn more about the nature of an abnormal rhythm by delivering pacing spikes at critical moments. It is even possible to find the origin of some of these abnormal rhythms by simply using pacing.


          The abnormal rhythms themselves are another aspect of what can be learned in the EP lab. There are a wide variety of arrhythmias that can occur in the human heart. Some are fairly common and some are quite rare. If you work in EP long enough, you will probably see them all. The mysteries of how these various rhythms work and what causes them can be pieced together by using the skills you have learned in the previous sections. This is how EP works, one skill unlocks the knowledge necessary to learn the next skill. And so, the learning process continues.


          The astute observer may have noticed that the sections outlined on this page coincide with the different sections that this web page is divided into. This is no coincidence. EP is not difficult to learn if you take the steps in the correct order. The lack of education in this field has forced many of us to learn things using a bit by bit approach. This method of learning is much more difficult and takes much longer. Over the years, I have had the opportunity to develop an educational program that is designed to impart the most important pieces of knowledge in the most effective order for those who are trying to learn EP. It is my goal, to one day set up a formal education program based upon the experiences that have taught me electrophysiology, presented in a logical order that is designed to decrease the perceived difficulty and increase the rate of achievement in this field. This web site is dedicated to that purpose.

          So read on. Read one page after the other and read them in order, even if you encounter a subject that you are already familiar with. Another view point can never hurt and you may learn something you didn’t know before. And if you find a piece of knowledge that appears to be missing from this site, please share it with us. For this site is for all those who strive to learn more about this wonderful field of medicine, and each of us has something to contribute

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