The V Wave and Y Descent

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1. When does RV contraction become too weak to continue pulling down the base? How does this affect right atrial pressure?

ANS: The phase of reduced ejection occurs in mid-systole. This attenuates the descent of the base and allows the filling of the right atrium from the venae cavae to raise right atrial pressure. This rise in pressure during systole is not named.

The C wave and X' descent. Most authors use the letter X to name both atrial relaxation and the fall in pressure due to the descent of the base, thus making the physiology of jugular contours difficult to understand.

2. What ends the rise in right atrial pressure and then allows the pressure to fall, thus making a wave?

ANS: Right ventricular relaxation allows RV pressure to fall below right atrial pressure, thus opening the tricuspid valve (at the end of isovolumic relaxation).

The right atrial pressure rises during the last third of ventricular systole when right ventricular contraction weakens and the descent of the base is diminished.

Period of reduced ejection begins

Period of reduced ejection begins

Right atrial pressure begins to rise
Tricuspid valve opens here

3. What name is given to the wave and the descent produced by filling of the right atrium during ventricular systole followed by diastolic emptying?

ANS: The V wave and Y descent.

4. Is the Y descent rapid or slow? Why?

ANS: Rapid. It reflects the rapid expansion phase of the RV.

5. What is meant by saying that an "atrioventricle" results from opening of the tricuspid valve?

ANS: When the tricuspid valve is open, the right atrium and ventricle form a common pressure chamber.

6. What happens to RV expansion after the end of the Y descent?

ANS: A slow mid- and late-diastolic expansion phase occurs and the pressure in the atrioventricle rises slowly as blood pours into the RV. The wave so produced is called the H wave.

Note: It is crucial to remember that the V wave is a systolic event occurring while the tricuspid valve is closed. It may help the novice to call the V wave a "villing" wave, i.e., a right atrial filling wave.

7. What name is given to the nadirs at the bottom of the X and Y descents? What is their significance?

ANS: They are the X and Y troughs. They have no significance except that some textbooks, unfortunately, do not name descents at all but simply give the letters X and Y to the troughs.

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