Negative waves in jugular venous pulse: March 2010
A wave
V wave
C wave
X wave
Ans. D: X waveAtrial pressure rises during atrial systole and continues to rise during isovolumetric ventricular contraction when the AV valves bulge into the atria. When the AV valves are pulled down by the contracting ventricular muscle, pressure falls rapidly and then rises as blood flows into the atria until the AV valves open early in diastole.The return of the AV valves to their relaxed position also contributes to this pressure rise by reducing atrial capacity. The atrial pressure changes are transmitted to the great veins, producing three characteristic positive waves in the record of jugular pressure.The a wave is due to atrial systole. As noted above, some blood regurgitates into the great veins when the atria contract, even though the orifices of the great veins are constricted. In addition, venous inflow stops, and the resultant rise in venous pressure contributes to the a wave.The c wave is the transmitted manifestation of the rise in atrial pressure produced by the bulging of the tricuspid valve into the atria during isovolumetric ventricular contraction.The v wave mirrors the rise in atrial pressure before the tricuspid valve opens during diastole.Venous pressure falls during inspiration as a result of the increased negative intrathoracic pressure and rises again during expiration.Careful bedside inspection of the pulsations of the jugular veins may give clinical information of some impoance. For examplein tricuspid insufficiency there is a giant c wave with each ventricular systole.In complete hea block, when the atria and ventricles are beating at different rates, the a waves that are not synchronous with the radial pulse can be made out, and there is a giant a wave ("cannon wave") whenever the atria contract while the tricuspid valve is closed.