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Which of the following components of central venous pressure tracings corresponds with systolic filling of the atrium?
The v wave on a central venous pressure (CVP) tracing is the result of increased venous return and systolic filling of the right atrium (RA).
Central venous pressure monitoring is important in both the operative and ICU settings. Central venous pressure is highly dependent on the intravascular volume and intrinsic tone of capacitance vessels within the venous system. It is usually equated to the right atrial pressure. Central venous pressure waveforms are classically defined by five phasic events: a, c, and v waves (peaks), along with x and y descents. These events function as markers of different mechanical events that occur within the cardiac cycle. Ultimately, CVP is used to assess right heart function and to evaluate blood volume. Normal values in the healthy supine adult patient range from 2 to 8 mm Hg.
The most prominent wave of the CVP tracing occurs during atrial contraction and is noted by the a wave, which is caused by the “atrial kick.” Atrial pressure then decreases, but a transient interruption of the pressure decline occurs as a result of isovolumetric ventricular contraction leading to bulging of the closed tricuspid valve (TV) into the RA, represented by the c wave at the start of systole. During ventricular systole, atrial relaxation occurs causing the x descent. Ventricular ejection gives rise to systolic venous filling of the RA, which is represented by the v wave. Lastly, as the TV opens and blood flows freely from the atrium to the right ventricle (RV), the y descent occurs (diastolic collapse). Occasionally, an h wave is noted in mid-late diastole if venous pressure is elevated in the presence of bradycardia.
Answer A: This corresponds to atrial contraction.
Answer B: This corresponds with atrial relaxation.
Answer C: This occurs at the start of systole.
Bottom Line: Normal CVP tracing summary:
a wave: atrial contraction, absent in atrial fibrillation
c wave: TV bulging into RA during RV isovolumetric contraction
x descent: TV descends into RV with ventricular ejection and atrial relaxation
v wave: venous return to and systolic filling of the RA
y descent: atrial emptying into RV through open TV
TrueLearn Insight : Below is a summary of the major CVP abnormalities: Disorder CVP waveform changes Atrial fibrillation Loss of a wave AV dissociation Cannon a wave Tricuspid regurgitation Tall c & v waves Loss of x descent Tricuspid stenosis Tall a & v waves Minimal y descent RV ischemia Tall a & v waves Steep x & y descent M or W configuration Pericardial constriction Tall a & v waves Steep x & y descent M or W configuration Cardiac tamponade Dominant x descent Minimal y descent
