Character

The JVP has ACXVY components:

• the A wave is due to right atrial systole; it coincides with the first heart sound and precedes the carotid pulsation
  
  
• the C wave is due to transmission of rapidly increasing right ventricular pressure before the tricuspid valve closes; it is small and rarely visible
  
  
• the X descent is due to relaxation of the right atrium
  
  
• the V wave is due to the venous return filling the right atrium as the tricuspid valve remains closed during ventricular systole:
  • it occurs simultaneously with the carotid pulsation
  • its height provides an indication of the right heart filling pressure
  • in cardiac failure, it is greater than 2 cm
  • an early V wave followed by a steep Y descent is a sign of tricuspid regurgitation
    
    
• the Y descent is due to opening of the tricuspid valve and rapid ventricular filling; a steep Y descent is seen in pericardial disease and tricuspid regurgitation

Thus, A, C, and V are positive deflections; X and Y are negative ones. From the start of the C wave to the Y descent, the ventricles are in systole.