Effects of enhanced sodium currents in mathematical model of heterogeneous myocardium

Cardiac arrhythmias and long QT syndrome may be associated with increased sodium currents. Possible effects of enhanced function of sodium channels on the transmural gradient in the electrical and mechanical properties of myocardium have not been sufficiently studied. We used our cellular mathematical models to investigate effects of an increased late sodium current on the electromechanical coupling in single subendocardial and subepicardial cells and in a strand of transmurally heterogeneous myocardium. Modeling results predicted that subepicardial cells are more vulnerable to rhythm disturbances than single subendocardial cells under these pathological conditions. Within the transmurally heterogeneous strand, mechanical and electrical interactions between such abnormal cells affected the patterns of electromechanical disturbances as compared to the single cells. This allowed myocardium to contract even in those conditions where single EPI cells lost contractility.