A model study of the effects of sodium conductance changes on the inducibility of cardiac reentrant activity

A decrease in sodium channel conductance has been traditionally associated with a reduction in the tissue excitability, and hence has been hypothesized to have an antiarrhythmic effect. Recently Starmer has proposed reduction in sodium conductance was not antiarrhythmic but rather would increase the vulnerable period and hence would be proarrhythmic. The authors used a sophisticated model of cardiac tissue to examine this possibility. Their results support Starmer's (1997) hypothesis. Reducing sodium conductance by a factor of 35% increased the vulnerable period by roughly 30%, and a decrease to 50% increased the vulnerable period by approximately 45%.