Expression of ion-channel subunit mRNA in different regions of canine right atrium

A trial electrophysiological heterogeneity, which plays an important role in the genesis and maintenance of atrial arrhythmia, is a major determinant of atrial reentrant arrhythmias. Recently, many studies on atrial flutter have demonstrated the anatomic architecture in the right atrium plays an important role in the genesis of atrial reentry. The crista terminalis （CT） in the right atrium, which is a unique anatomic structure of the right atrium, provides an area for conduction block and delay, leading to initiation, maintenance, and termination of atrial arrhythmias. Catheter ablation of CT can successfully eliminate these atrial arrhythmias. These literatures contrast with limited knowledge of the basic electrophysiological properties of CT and how these promote arrhythmia generation. Compared to pectinate muscles （PM） and right atrial appendage （RAA）, CT have distinct electrophysiological properties related to different densities of several ionic currents, the transient outward current （Ito） and L-type Ca^2＋ current （Ica-L） underlie the bulk of the different densities of several ionic currents. Cardiac Ito and Ica-L play a major role in action potential repolarization. Ito is particularly important in early （phase 1） repolarization and influences the participation of other currents. It is generally believed that Ica-L plays an important role in the plateau phase of repolarization. However, the mechanisms for these ionic current differences are unknown. One possible is a difference in ion channel subunit expression, but virtually no data are available regarding ion-channel subunit expression in CT, PM, and RAA. The Kv4.3 channel underlies the bulk of the α-subunit of Ito in canine and human heart.

Expression of ion-channel subunit mRNA in different regions of canine right atrium