The jugular venous pressure.
The jugular venous pressure.
The jugular venous pressure (JVP) can yield valuable information about cardiac function (especially of the right ventricle) and pulmonary function and is an important component of the assessment of volume status. The JVP is most commonly elevated with a raised venous pressure due to cardiac failure or hypervolaemia.
In principle, the JVP reflects the height of the column of venous blood that rises above the physiologic zero point, which corresponds to the right atrium in humans. In practice it is necessary to estimate the position of the right atrium, by one of two techniques:
The angle of Louis/ sternal angle
This is the quickest and most commonly used method. The sternal angle lies about 5 cm above the center of the right atrium In normal persons the venous column of blood will normally not rise more than 1 to 2 cm above the sternal angle, irrespective of position (corresponding to a right atrial pressure of about 7 cm H2O). Therefore a venous column rising three or more centimeters above the sternal angle is suggestive of a raised right atrial filling pressure.
The Phlebostatic axis
This is the point at the level of the 4th intercostals space midway between anterior and posterior surfaces of the chest. While there is some theoretical advantages to using this point in the estimation of JVP it is of less value at the bedside simply because it is easier to get agreement between examiners as to the location of the sternal angle.
An approach to examining the JVP is described below.
A strategy for examination
The patient is positioned so that the upper body rests at about 45 above horizontal. (Include figure) > Good lighting is important, and light falling tangentially on the right neck (e.g. from a torch or flashlight) can help identifiy the JVP. The head is turned slightly towards the left shoulder. Inspect the right side of the neck for the appearance of a double venous flicker just medial to the sternocleidomastoid muscle . The collapse or descent in the venous wave form is often more easily appreciated (whereas an outward pulse is often the carotid pulse). The external jugular is often seen as a cord, and can provide an indication of an elevated JVP, but often does not translate the venous waveform well due to compression of this vein by external structures The JVP is easier to see slim or young people and is is more difficult to see in an obese person, or a person with a short or bull-neck.
A markedly high JVP may be missed because the venous flicker is occurring above the angle of the jaw. In this case, the top of the waveform may be seen by sitting the patient up at 90°. Alternatively, look at the patient’s earlobes - If these move with the characteristic double flicker of a raised JVP then the venous column is very likely to be elevated above the angle of the jaw.
The abdominojugular reflex
If the jugular venous movements are not apparent, apply gentle pressure over the mid-abdomen and look for the JVP at the neck for about 10 seconds Normally this manouvre does not affect the JVP, or if it does so, only for a few seconds. If the JVP rises by 4 or more centimeters and remains elevated for the duration of the abdominal compression then this is suggestive of raised right atrial pressure or reduced atrial compliance.
This is a rise in the JVP seen with inspiration. It is the opposite of what is seen in normal people and this reflects the inability of the heart to compensate for a modest increase in venous return. This sign is classically seen in constrictive pericarditis in association with a raised JVP. This condition was originally described in tuberculous pericarditis and is rarely seen. Kussmauls sign is also seen in right ventricular infarction, right heart failure, tricuspid stenosis, and restrictive cardiomyopathy. It is not seen in acute cardiac tamponade- although it may be seen if tamponade occurs with a degree of constricive pericardiditis.
Interpretation of the venous wave form
The bedside observer can detect two distinct positive waves (a, and v) and negative waves, or descents of movement (x’ and y). A third, c wave is seen in venous waveforms measured using transducers (c for the positive wave and x for the preceding descent).
The a wave is produced by contraction of the right atria and is the most prominent. The x descent follows occurs during atrial relaxation. After the ventricle begins to contract, initially producing the C wave, the prominent x’ descent is produced as the right atrium is pulled inferiorly by the contracting ventricle. The v wave is produced by filling of the right atrium during ventricular systole against a closed tricuspid valuve. This is followed by a second prominent y descent which is produced during the emptying of the atrium into the ventricle during diastole. Hence the x’ descent occurs in systole and the y descent occurs in diastole. The a wave occurs in late diastole and the v wave occurs in late systole.
The individual components of the venous wave may be helped by simultaneously auscultating the heart sounds, or by palpating the carotid pulse to determine systole and diastole. The x descent ends just before the S2 (the second heart sound), while the y decent begins just after it. The x’ is systolic and coincides with the carotid pulse, while the y is diastolic and begins a short while after the carotid pulse. Now look for the outward waves of movement. Some abnormalities are described below.
Abnormalities of Jugular venous wave form
Examples of abnormalities of the descents
x’less than y
This is seen in atrial fibrillation, where the a wave is lost. Mild tricuspid regurgitation will also result in reduced prominence of the x’ descent. During ventricular contraction backflow of ventricular pressure due to an incompetent valve offsets the drop in venous pressure usually produced by downward movement of the atrium.
The x’ descent is usually more prominent than the y descent. If they are of approximately equal size it suggests that the y descent is unusually prominent. This is seen in constrictive pericarditis, and atrial septal defect
This may be a normal finding if the JVP is not elevated. Tricuspid stenosis can also result in the disappearance of the y descent.
"Rapid y descent"
This is a prominent y descent in the presence of a normal x’ descent. It is a good sign of constrictive pericarditis or restrictive disease of the right heart.
Abnormalities of the a or v waves
"Giant s waves"
These precede the S1, and occur with every beat and indicate outflow obstruction such as tricuspid or pulmonary valve stenosis, and pulmonary hypertension.
"Canon a waves"
These are distinct from giant a waves. These occur with dissociation of atrial contraction and ventricular contraction, so that the atria contract against a closed tricuspid valve. Unlike giant A waves, canon A waves occur only occasionally rather than with every beat.
Tricuspid incompetence, often seen in pulmonary hypertension, is associated with very prominent jugular venous pulsations that lack an x or x’ descent. They consist of a single outward systolic movement that occurs concurrently with the carotid pulse and collapses in early diastole, just after the S2. The absence of an x descent allows them to be distinguished from giant A waves.