Inhibition of the Na pump--a mechanism in the genesis of cardiac arrhythmias.

An ATP-driven Na pump maintains the unsymmetrical Na and K distribution across the cell membrane of cardiac cells. An increase of the intracellular Na or extracellular K concentration enhances this active Na transport. About 35 per cent of the actively transported Na is ejected from the cells as a hyperpolarizing outward current. The Na pump influences the cardiac Ca metabolism via the Na-Ca exchange. Inhibition of the pump affects the generation and conduction of the cardiac action potential by various mechanisms. It seems to be involved in the genesis of cardiac arrhythmias.