Computer-model analysis of the effect of potassium changes on the sinus node pacemaking

It is well know that sinus node pacemaker activity is strictly related to the autonomic outflow, but the role of plasma potassium level on sinusal pacemaking is not yet well understood. A computer model of the sinus node cell was used to analyze heart rate data collected during purely diffusive hemodialysis, which allowed large changes in extracellular potassium concentration to be achieved without eliciting notable changes in the autonomic modulation. Model-based analysis revealed that changes of potassium concentration can cause large heart rate variations (from 60 to 90 bpm). According to experimental data, a significant heart rate increase was predicted by the model after potassium decrease and calcium and pH increase. A highly non-linear heart rate dependence on potassium was also recognized and its relationship with calcium and pH levels was disclosed. It was concluded that potassium changes in physiological range have an important, complex, impact on the pacemaking rhythm independently of autonomic outflow.