The marginal ridge is located on the lateral wall of the right atrium, which is a muscular bulge from the front of the superior vena cava to the front of the inferior vena cava, and continues with the Euclidean ridge (EV) in the front of the inferior vena cava. At 6 ~ 8 weeks after embryo development, the right angles of venous sinus, superior vena cava and inferior vena cava merge with the original atrium to form CT, and the right atrium is divided into smooth part dominated by the original venous sinus and trabecular muscle part dominated by the original atrium. Pacing cells in the original pacing area also concentrated in the upper right atrium and upper CT with the movement of venous sinus.
The relationship between the unique anatomical structure of the right atrium and electrophysiological phenomena has been discussed. CT first attracted the attention of electrophysiologists from 1909 to 1963. Originated from the posterior margin of sinoatrial node, descended along CT and continued to EV. In the process of CT internal conduction, the impulse extends laterally like a tree to dominate the dorsal side of the right atrium and extends forward like a fan to continue the trabecular muscle.
Intracardiac morphology:
Intracardiac morphology of CT is not uniform. Kalman et al. examined the right atrium of 27 patients with arrhythmia by catheter intracardiac echocardiography, and found that the anatomical position of CT changed greatly, which was different from that of catheter positioning under X-ray. The intracardiac morphological changes of CT were also obvious, showing that only 1/3 on CT was completely uplifted, and 44% of them continued to uplift on CT. Only nearly 26% of the patients showed protrusion on full-segment CT, while 74% of the patients did not show intracardiac protrusion on middle and lower 1/3 CT, but only showed the boundary between trabecular muscle and smooth muscle.