A fibroblast-myocyte model which accounts for slow conduction and fractionated electrograms in infarct border zones

Biophysical mechanisms behind the fractionated character of cardiac electrograms from infarct border zones have not been clearly identified. The working hypothesis of this study is that fibroblasts in the scar tissue are electrically coupled to myocytes via gap junctions, acting as RC connections between healthy cardiac cells. This study examined the physical characteristics of cultured fibroblasts and calculated an average surface area of 74.4 E-5 cm². Using reported gap junction conductance for myocyte-fibroblast-myocyte triplets, typical myoplasmic resistivity, and specific capacitance yields a total RC time constant in the range of 35-40 ms. This would cause major delays in propagation between two healthy myocytes conjoined by a fibroblast, and could explain phenomena such as micro-reentry and the fractionated electrogram.