There are two outward-moving waves (the a and v wave) and two inward-moving waves (the x and y descent).
• The 'a' wave is caused by atrial contraction and is presystolic. It can be identified by simultaneous auscultation of the heart and the examination of the jugular venous pulse. The 'a' wave occurs at about the first heart sound.
• The 'c' wave is due to closure of the tricuspid valve and is not readily visible.
• The 'v' wave results from venous return to the right heart (not due to ventricular contraction) and occurs nearer to the second heart sound.
• The 'x' descent is due to atrial relaxation (sometimes referred to as systolic collapse).
• The 'y' descent is produced by opening of the tricuspid valve and rapid inflow of blood into the right ventricle.