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


Understanding the Language of EP...

          The second major area of study that must be completed is specific to electrograms. Everything that we determine regarding the rhythms that occur in the heart is specific to what we can determine from these recording of the electrical activity that governs how the heart functions. This section is dedicated to learning about electrograms and how to understand the information they contain.

Electrograms Defined - The best place to start in our quest to understand electrograms is a description of what an electrogram is. The following subjects are covered in this section;

Graphing Voltage over Time
The Isoelectric Line
The Ground - what it is, why we need it
The Driven Reference

Recording Modes - This is where we learn about the true difference between what unipolar and bipolar electrograms. There are numerous misconceptions regarding what the difference between these two recording modes really is. If you think it has to do with electrode spacing, guess again.

They All have Two Electrodes
The Zero Potential Reference
Unipolar Electrograms
Bipolar Electrograms

Electrode Spacing - This section is specific to bipolar electrograms and how adjusting the space between the electrodes affects what we see. This is the section that describes why so many people believe that the difference between unipolar and bipolar is nothing more that the distance between the electrodes, and also why that assumption is incorrect.

The Electrogram with Zero Space between the Electrodes
The Electrogram with 2mm Between the Electrodes
How Far is Too Far?

Filters - All electrograms are filtered. The more you understand about this process, the stronger your performance in the lab will be.

The Low Pass Filter
The High Pass Filter
The Band Pass Filter
Bipolar Filter Settings
Unipolar Filter Settings
Notch Filters

Unipolar theory - Now that we know about the difference between unipolar and bipolar electrograms, it is time to start learning how powerful unipolar electrograms are and why those who understand them have a step up over those who do not.

Local Activation - When dealing with both unipolar and bipolar electrograms, it is essential to be able to pinpoint where on the electrogram activation of the local myocardium really occurs. Do you map bipolar EGM's at the onset? Find out why you are mapping a location that is not the true location of local activation.

Activation Sequence - Activation sequence is the process of analyzing the local activation of numerous electrograms and determining the order in which different regions of the heart depolarize. This is an essential process of arrhythmia analysis.

Voltage - Learn about the difference between voltage measured by unipolar and bipolar electrograms. What is the difference between Peak to Peak voltage and Peak Negative voltage? Why are unipolar and bipolar measured differently? This section answers these questions.

Morphology interpretation - The morphology of all electrograms provides a great deal of information on what these signals are showing us. In this section learn how to pinpoint the point of early activation using both unipolar and bipolar electrograms. Also learn how unipolar EGM's will show when activation is from outside the chamber, an essential tool for determining epicardial or alternate chamber origians.

Arrhythmia Analysis - Now that all the tools are in place, we can review the process of using what we know to help us determine the nature of each arrhythmia.

Surface EGM's - This section looks at the electrocardiograms recorded from surface based electrodes.

Intracardiac EGM's - With electrodes placed inside the heart we gain the ability to view intracardiac electrograms. This section reviews the information specific to these recordings.




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