Safety factor in simulated 2D cardiac tissue. influence of altered membrane excitability

The safety factor (SF) is an indicator of the safeness of electrical conduction in the myocardium. In the present work, the estimation of the SF based on the formulation proposed by Shaw and Rudy (1997) has been extended to 2D (SF-2D) and evaluated. Furthermore, the effect of the increment of extracellular potassium concentration ([K+]o) on the SF-2D of a convex wavefront has also been studied and compared with the results published by our group for 1D strands (SF-1D). Our results revealel that a) the SF-2D is sensitive to variations of membrane excitability and its value drops below unity whenever failure of conduction occurs, b) the SF-2D shows a biphasic behavior with [K⁺]_o, which is consistent with the supernormal conduction phenomenon, and c) compared with the SF-1D, the SF-2D for a convex wavefront is less sensitive to [K⁺]_o and reaches smaller values.