The phrase "right atrium" refers to a part of the heart. It is the upper chamber on the right side of the heart that receives blood from the body before it is pumped to the lungs to collect oxygen. Full definition
In those cаses when there is rupture of the tricuspid valve and massive regurgitation, the increased pressure in right atrium leads to rupture of the septum and right to left shunt. (balkanvets.com)
The left and right atria receive blood from the lungs and body respectively. (2ndchance.info)
So we decided to use pulmonary hypertension properly and make the dose of sildenafil lower — 1 mg / kg / 24 h. with presumption that higher right ventricle and right atrium pressure will make the amount of the shunt lower. (balkanvets.com)