在心肌细胞中，Ca（2+）浓度在收缩时的高水平和舒张时的低水平之间交替收缩过程中ca（2+）浓度的增加主要是由于细胞内储存的ca（2+）释放所致。然而，一些Ca（2+）也通过肌膜（质膜）进入细胞在松弛过程中，ca（2+）被隔离在细胞内的储存中。为了防止细胞内存储物超载，必须从细胞中挤出穿过肌膜的Ca（2+）Na＋-Ca（2＋）交换剂是Ca（2＋）在弛豫过程中从细胞中挤出的主要机制在心脏中，交换器可能在洋地黄作用中起关键作用。心肌细胞兴奋后，交换器是使心肌细胞恢复静息状态的主要机制。
In cardiac myocytes, Ca(2+) concentrations alternate between high levels during contraction and low levels during relaxation. The increase in Ca(2+) concentration during contraction is primarily due to release of Ca(2+) from intracellular stores. However, some Ca(2+) also enters the cell through the sarcolemma (plasma membrane). During relaxation, Ca(2+) is sequestered within the intracellular stores. To prevent overloading of intracellular stores, the Ca(2+) that entered across the sarcolemma must be extruded from the cell. The Na(+)-Ca(2+) exchanger is the primary mechanism by which the Ca(2+) is extruded from the cell during relaxation. In the heart, the exchanger may play a key role in digitalis action. The exchanger is the dominant mechanism in returning the cardiac myocyte to its resting state following excitation.[supplied by OMIM, Apr 2004]