The lateral wall is generally considered to include the wall of the right atrium from the ostia of the superior and inferior vena cava anteriorly to the ostium of the right appendage or auricle. The endocardial surface of the lateral wall includes both smooth muscle, in the posterior region between the vena cava and the crista terminalis, and pectinate muscle from the crista terminalis into the right atrial appendage. The anterior region of the lateral wall, surrounding the ostium of the right appendage, is often referred to as the right atrial free wall.
Importance in cardiovascular diseases:
The right atrial lateral wall is considered by some to have a role in the genesis of several atrial arrhythmias, including atrial reentry and focal atrial tachycardia.
Importance in device delivery:
The lateral wall is sometimes used to place right atrial pacing leads. The anterior aspect of the lateral wall is one of the thinnest walls of the heart, resulting in a higher than usual risk for perforation when extracting a lead from this location.