TLX2 and atrial fibrillation: For example, Lee et al. compared the impact of ionic processes on APD in control and AF-remodeled cells and found that the Na+/Ca2+ exchanger (NCX) current has little influence on APD in control cells but more markedly impacts AF cells; the analysis also revealed that IK1 upregulation plays a dominant role in APD shortening in AF, and that the L-type Ca2+ current (ICaL) significantly contributes to rate-dependent APD changes in both control and AF myocytes (Lee Y. S. et al., 2016).