An intuitive safety factor for cardiac propagation.

Safety factor is a useful concept for analyzing the propagation of impulses through cardiac tissue, which may have compromised ion channel function or electrical connectivity. Several formulations for its calculation have been proposed and have proved useful in one dimension; however, as we demonstrate, recent attempts to use the same formulation in multiple dimensions have led to questionable conclusions. In this study, we mathematically analyze the latest formulation of safety factor and explain its puzzling behavior. We propose a new formulation that is suitable for any dimension and can be estimated from experimental measurements. Its applicability is verified in two-dimensional simulations. (c) 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.