The role of approximate entropy in predicting ventricular defibrillation threshold

Area of Science:

• Cardiovascular Physiology
• Electrophysiology
• Medical Engineering

Background:

• The impact of myocardial tissue mass on the ventricular defibrillation threshold (DFT) remains incompletely understood.
• It is hypothesized that alterations in tissue mass influence DFT by modifying the regularity of ventricular fibrillation (VF) wavefronts, quantified by entropy.

Purpose of the Study:

• To investigate the relationship between myocardial tissue mass and ventricular defibrillation threshold (DFT).
• To determine if changes in tissue mass modulate DFT by altering ventricular fibrillation (VF) wavefront regularity (entropy).

Main Methods:

• Isolated pig right ventricles (RV) were used, with progressive tissue mass reduction.
• Optical mapping with voltage-sensitive dyes assessed activation wavefronts during VF.
• Defibrillation threshold (DFT) was determined using an up-down algorithm.
• Approximate entropy (ApEn) was calculated from VF electrograms.

Main Results:

• Significant reduction in DFT, ApEn, and activation wavefront numbers occurred when RV mass was reduced near the critical mass for VF maintenance.
• DFT energy decreased by 27% with substantial mass reduction.
• A significant correlation was found between DFT and ApEn, with ApEn increasing near the critical mass.

Conclusions:

• Tissue mass reduction significantly lowers DFT when it enhances VF wavefront regularity.
• These findings suggest that myocardial mass is a critical determinant of VF dynamics and defibrillation efficacy.