A mechanism for the upper limit of vulnerability

Area of Science:

• Cardiac electrophysiology
• Computational modeling

Background:

• The upper limit of vulnerability (ULV) is the strongest shock inducing cardiac reentry.
• Understanding ULV is critical for effective defibrillation strategies.

Purpose of the Study:

• To investigate the underlying mechanism of the upper limit of vulnerability (ULV).

Main Methods:

• Numerical simulations of cardiac tissue using the bidomain model.
• Application of S2 shock during the refractory period of S1 action potential.
• Comparison of smooth versus smooth plus random fiber geometries.

Main Results:

• ULV was absent with smooth fiber geometry alone.
• ULV was present when random fiber geometry was included.
• The difference is attributed to the shock-induced break wave front's interaction with the virtual anode.

Conclusions:

• Local tissue heterogeneities are critical for ULV.
• Heterogeneities influence the fate of shock-induced wave fronts at the virtual anode.
• These findings highlight the importance of tissue structure in cardiac arrhythmogenesis.