atrial

1. Of or relating to an architectural atrium.
2. Of or relating to an anatomical atrium.

Of or relating to an atrium.

Pertaining to an atrium.

• a. contraction — contraction of the atrial muscle; plays a part in ventricular filling and opening and closing of the A-V valves.
• a. filling — return of blood via the venae cavae and the pulmonary veins to the atria. Too slow a return means inadequate cardiac output, too slow emptying means an increase in central venous pressure and possibly the development of congestive heart failure. The rate varies normally with the cardiac cycle, being fastest during atrial diastole and slowest during atrial systole.
• a. natriuretic factor (ANF) — a peptide hormone found in cardiocytes of the right and left atria and released in response to increases in plasma volume. Plays a role in the regulation of blood pressure and volume, and in the excretion of water, sodium and potassium. Closely related or possibly identical substances include auriculin, atriopeptin, cardionatrin.
• a. rupture — most often is a complication of endocardiosis and valvular insufficiency in dogs. The resulting acute pericardial hemorrhage may cause death from cardiac tamponade.
• a. septal defect — a congenital heart defect in which there is persistent patency of the atrial septum, owing to failure of closure of the ostium primum or ostium secundum.
• a. standstill — complete lack of atrial contraction; ventricular function remains normal. Caused by hyperkalemia, extreme sinus bradycardia, digitalis toxicity and a congenital muscle disorder of dogs and cats.
• a. systole — see atrial contraction (above).

The adjective has one meaning:

Meaning #1: (anatomy) of or relating to a cavity or chamber in the body (especially one of the upper chambers of the heart)
  Pertains to noun: atrium (meaning #1)