Unipolar atrial electrogram morphology from an epicardial and endocardial perspective

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Anatomy

Background:

• Endo-epicardial asynchrony (EEA) plays a role in atrial arrhythmias.
• Morphologic differences between epicardial and endocardial atrial electrograms are not well-described.
• Electrogram morphology may indicate the presence of EEA.

Purpose of the Study:

• Directly compare epicardial and endocardial unipolar electrogram morphology during sinus rhythm (SR).
• Evaluate if EEA contributes to electrogram fractionation.
• Correlate fractionation with spatial activation patterns to understand EEA's role.

Main Methods:

• Simultaneously recorded unipolar electrograms from epicardium and endocardium in 26 cardiac surgery patients.
• Analyzed electrograms from the right atrial (RA) free wall during SR for differences in activation time, voltage, RS ratio, and fractionation.
• Assessed surrounding electrograms to determine if fractionation originated from EEA.

Main Results:

• The superior RA showed delayed activation, EEA, and fractionation.
• Epicardial and endocardial electrograms exhibited S-predominance, with similar fractionation patterns.
• Remote activation caused most fractionation (95%), with 4% attributed to EEA.

Conclusions:

• Local endo-epicardial differences in electrogram fractionation occur occasionally in SR but may increase during arrhythmias.
• Electrogram fractionation can originate from EEA.
• Unipolar electrogram fractionation may serve as a potential marker for identifying EEA.