If you have any questions about the EP Lab, Let us know. | Source 1: Cardiac Electrophysiology – From Cell to Bedside 3rd Edition; Douglas P. Zipes, MD and Jose Jalife, MD ISBN # 0-7216-7811-4 Cell to Bedside has long been one of the definitve resources for those who work in the electrophysiology labratory. This book is not for beginners as it presents a depth of knowledge that is often difficult to grasp without extensive experience. If you have been working in EP and are seeking to expand your knowledge beyond the basics, the this book is a must. |
| Source 2: Cardiac Pacing - Edited by Kenneth A. Ellenbogen; ISBN 0-86542-184-6 This book comes is one of the early pacing texts. I found information in here regarding unipolar and bipolar sensing that was worth adding to this section. This topic will be expounded in the section on intracardiac electrograms. |
| Source 3: Clinical Electrocardiography, a Simplified Approach - 7th Edition / Ary L. Goldberger ISBN This is a good resource for those who are new to interpretting the surface electrocardiograms. This was one of the few books where I found information on the specific electrode hookups for unipolar and bipolar. |
| Order these books at Cardiotext.com If you are looking to add any of these texts to your library, click on the link above to visit the Cardiotext website. Select the section on Electrophysiology to see some of the latest titles available. |
How do we read those strange little signals?
Throughout this section on electrograms, we have explored how these signals are recorded and how, by adjusting the parameters utilized during the recording process, we can adjust the recording output to show us different levels of information. Before we move on to determining how to interpret electrograms, we should stop and take a minute to review the information we have learned.
Electrogram Defined: On this page, we discussed how an electrogram is a graph of voltage over time. From the action potential through intracardiac signals to the surface ECG's, electrograms show changes in voltage over a given period of time. We showed how the sampling rate can affect the information we can obtain from electrograms and reviewed the dual roles of the ground used in most systems that record electrograms.
Recording Modes: Here we looked at the similarities and differences between unipolar and bipolar recordings. Remember that both types of electrograms are obtained using the exact same methods; two unipolar electrograms are recorded, one at the positive electrode and one at the negative electrode. The negative electrogram is subtracted from the electrogram recorded at the positive electrode and the difference between these two is filtered and then displayed. The negative electrode for a unipolar electrogram is placed at a location where there is zero potential, or no electrical activity and thus, has no information to be subtracted from the data collected at the positive electrode. The result is a wide open view of all electrical activity surrounding the positive pole. Bipolar electrograms are produced using the
Bipolar shows local activation at peak and indicates timing of local activity only. Discuss split or fractionated egm's and cfe's
Unipolar shows three things, signal strength, velocity and direction
Unipolar R wave approaches, Q indicates moving away
Local activation occurs when the egm goes negative from the isoelectric line
Hidden R wave...
Hold
After bipolar is done go back to pvc and discuss unipolar information from surface - EGM Interpretation
1. direction
a. P wave in lead I
b. RVOT pvcs in II, III and aVF
2. amplitude
a. use His A, H and V – three different amplitudes on same catheter
b. what do each look at
3. conduction velocity
a. action potential phase 0
b. AP phase 1-3
c. QRS (phase 0 in all of V)
d. T wave (phase 1-3 in all of V)
