Preshock phase singularity and the outcome of ventricular defibrillation

Area of Science:

• Cardiology
• Biophysics
• Medical Imaging

Background:

• Phase singularity (PS) is a critical topological defect and a known driver of ventricular fibrillation (VF).
• The precise relationship between the quantity of preshock PS and the success of defibrillation remains incompletely understood.

Purpose of the Study:

• To investigate whether the number of PSs present at the time of defibrillation shock delivery significantly influences the outcome.
• To test the hypothesis that PS quantity is a determinant factor in successful defibrillation.

Main Methods:

• Optical mapping using a potentiometric dye (di-4-ANNEPS) was employed in isolated, perfused rabbit hearts (n=7).
• Ventricular fibrillation was induced for short (10 seconds) and long (1 minute) durations, followed by shock delivery.
• Defibrillation outcomes were categorized into type A (immediate termination), type B (postshock repetitive responses), and unsuccessful.

Main Results:

• In short VF, shocks successful for type A had fewer preshock PSs (0.3 ± 0.4) compared to type B (1.4 ± 0.3) and unsuccessful shocks (1.5 ± 0.4).
• In long VF, preshock PS numbers were significantly higher for type A (1.7 ± 0.5) versus type B (3.0 ± 0.5) and unsuccessful shocks (3.5 ± 0.6).
• All preshock PSs were eliminated by the shock, but rapid reinitiation of activity occurred in unsuccessful and type B shocks, unlike type A.

Conclusions:

• A low or absent number of preshock PSs is strongly associated with successful type A defibrillation.
• No significant difference in preshock PS numbers was observed between unsuccessful and type B successful defibrillation outcomes.