[TA] ascending atrial branch, usually (55%) arising from the anterior stem of the right coronary artery (but 35-45% arising from the circumflex branch of the left coronary artery), which runs around the base of the superior vena cava to reach the sinuatrial node. SYN: ramus nodi sinuatrialis arteriae coronariae dextrae [TA], artery to the sinuatrial (S-A) node, branch to sinuatrial node, sinuatrial nodal artery, sinuatrial nodal branch of right coronary artery, sinuatrial node artery, sinus node artery.