Quantifying APD-ARI Differences Across Endo-Epicardial Surfaces in Human and Porcine Hearts

Area of Science:

• Cardiovascular Physiology
• Electrophysiology
• Biomedical Engineering

Background:

• Accurate measurement of cardiac repolarization is vital for understanding heart function and disease.
• Activation-Recovery Interval (ARI) from unipolar electrograms is a commonly used electrical surrogate for Action Potential Duration (APD).
• Previous studies have not fully elucidated the layer-dependent accuracy of ARI methods across different species and cardiac conditions.

Purpose of the Study:

• To compare the accuracy of ARI measurements derived from unipolar electrograms against optically measured APD.
• To investigate layer-specific differences (endocardial vs. epicardial) in ARI-APD agreement.
• To evaluate the performance of different ARI calculation methods.

Main Methods:

• Simultaneous optical and unipolar electrogram recordings were obtained from healthy porcine and pathological human hearts.
• High-speed cameras and transparent electrode arrays were utilized for signal acquisition.
• Action Potential Duration (APD) was measured optically at 70-90% repolarization (APD70, APD80, APD90).
• Activation-Recovery Interval (ARI) was calculated using the Wyatt method and an alternative method.

Main Results:

• Layer-dependent differences in ARI-APD agreement were observed in both species.
• In pigs, the Wyatt method best matched endocardial APD, while an alternative method better matched epicardial APD.
• In humans, the alternative method showed closer agreement with APD90 (endocardium) and APD80 (epicardium).

Conclusions:

• Estimating cardiac repolarization using ARI requires surface-specific methodologies.
• Neither the Wyatt nor the alternative ARI method consistently provided accurate APD measurements across all layers and conditions.
• These findings underscore the importance of selecting appropriate ARI measurement techniques based on the specific cardiac layer and clinical context.