Evaluation of electrode-tissue contact using multifrequency impedance analysis and Cole-Cole model fitting

Area of Science:

• Biomedical Engineering
• Cardiac Electrophysiology
• Medical Device Technology

Background:

• Atrial fibrillation (AF) ablation success relies on catheter-tissue adhesion.
• Current methods (ECI, IR) lack insight into internal tissue changes during compression.
• Accurate characterization of catheter-tissue contact is crucial for effective ablation.

Purpose of the Study:

• To introduce a novel method using multi-frequency impedance and Cole-Cole modeling.
• To investigate internal tissue changes during compression for improved catheter contact assessment.
• To correlate impedance measurements with applied pressure for better understanding of catheter-tissue interaction.

Main Methods:

• Employed a four-electrode impedance measurement system with a customized circuit and compression platform.
• Applied varying pressures (5-400 g) to biological tissue samples (bullfrog thighs).
• Collected impedance data across a frequency range (500 Hz-100 kHz) and analyzed using Cole-Cole model fitting.

Main Results:

• The customized circuit demonstrated high accuracy in impedance detection (error < 6% in model components).
• A significant linear relationship (Pearson R ≈ 0.9, p < 0.05) was found between extracellular fluid resistance and applied pressure.
• Extracellular fluid resistance was observed to increase proportionally with increasing compression pressure.

Conclusions:

• Multi-frequency impedance combined with Cole-Cole modeling provides a new method to assess catheter-tissue contact.
• The positive correlation between extracellular fluid resistance and pressure offers a novel metric for evaluating contact quality.
• This approach has the potential to enhance the understanding and success rates of AF ablation procedures.