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Six Terms that Decode the Funky Signals of Arrhythmias

Describing the squiggly lines that keep our eyes open during EP procedures!

In cardiac electrophysiology, you will hear various non-scientific terms to describe signals – funky little blip (FLB), juicy, the hot spot, etc. Even the “scientific” descriptions of the overall appearance of abnormal intracardiac EGMs can leave you a bit cross-eyed! However, these descriptions can be great clues to the mechanism or cardiac substrate involved in the arrhythmia. In this blog, we will review terms that properly describe complex electrograms and their characterizing features.


1. Fractionated Electrogram:

Fractionated intracardiac signals

Fractionated refers to an electrogram with multiple deflections or components, indicating s l o w e d conduction or tissue heterogeneity.


2. High-Frequency Content: 

High-frequency intracardiac signals

Components of an electrogram that display high-frequency or could represent rapid oscillations.


3. Low Amplitude: 

Low amplitude signals indicate a low voltage or a small deflection in the electrogram, suggesting reduced electrical activity.


Are you still trying to unscramble the EP monitor signals? Try this online self-paced course: Electrogram Essentials: The Long and the Short of EGMs available in the CHART Course Store. GROW Members save 20%.


4. Late Potentials: 

Late potentials intracardiac signals

Delayed or prolonged electrical activity in the cardiac cycle, which is often associated with scar tissue or abnormal conduction pathways. Late potentials indicate delayed and fractionated components that occur later in the cardiac cycle (extra-systolic).


5. Double Potentials:

These signals represent the presence of two distinct deflections in a single electrogram, suggesting conduction block or dual pathways. When a single electrogram splits into two or more components, it indicates delayed or fractionated conduction.


6. Continuous Fractionation: 

Continuous or prolonged fractionation pattern in the electrogram. Describes electrograms with complex patterns, often associated with arrhythmogenic substrates. *Also referred to as Complex Fractionated Electrogram.


The relevance of complex electrograms lies in their ability to help clinicians assess and diagnose various cardiac conditions. Describing complex intracardiac electrograms can be confusing. Being able to connect the appearance of the EGM can provide valuable information about the electrical activity within the heart. 


EP Procedure Pacing: Life in the Fast Lane is an online self-paced course that will continue your learning about cardiac electrograms and advanced pacing maneuvers.

If you found this interesting and couldn't stop reading, you might be an EP Nerd! Join the rest of us EP Nerds in the GROW Membership at CHART Healthcare Academy! The Membership includes monthly virtual CEU courses facilitated by people just like you who love EP and are determined to share their knowledge. CHART Live Events. #EPpro


Steph Jasa


Steph serves as the #chiefNERD for the CHART team. She has more than 20 years of experience in cardiology, including time in the hospital setting, industry, and consulting for cardiology companies. Her passion for providing education and training is underpinned by a desire to take complex concepts and make them easy to understand and apply in the clinical setting.

Connect with Steph on LinkedIn for information about CHART Healthcare Academy, Cardiac Electrophysiology and Cardiac Device Clinic training and education programs.



  1. Issa, Z., Miller, J. M., & Zipes, D. P. (2018). Clinical Arrhythmology and Electrophysiology (3rd ed.). Elsevier - OHCE.

  2. Huang, S.K. S., & Miller, J. M. (2019). Catheter Ablation of Cardiac Arrhythmias (4th ed.). Elsevier – OHCE

  3. Stevenson, D.Z.J.J. W. (2017). Cardiac Electrophysiology: From Cell to Bedside - Electronic (7th ed.). Elsevier

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