Jugular Venous Pressure
Understanding the physiology and ultrasound evaluation of the JVP
This chapter comes in this place in the text book for several reasons. First, the physiology discussed is important for understanding a variety of cardiac pathologies. Second, the JVP should be evaluated first in many patients having cardiac POCUS. Third, it nicely uses the color flow Doppler (CF) concepts discussed in the previous carotid artery chapter.
Right atrial pressure (RAP) and central venous pressure (CVP) are measured invasively in the supine position with a pressure transducer catheter. The pressure is usually reported as a mean (normal = 2-6 mm Hg) but normal peak pressure of an a-wave is about 10 mmHg. The RAP/CVP varies throughout the cardiac and respiratory cycles and specific variations can have diagnostic importance. Atrial fibrillation (lack of an a-wave), tricuspid regurgitation (large v-wave), and Kussmaul sign (rise in pressure with inspiration instead of a fall) would be specific examples.
The phlebostatic zero point for the heart (middle of the right atrium) was defined decades ago and lies reliably at the intersection of a horizontal line from the fourth intercostal space at the sternum with the vertical mid-axillary line. This zero point is roughly static for any position from supine to sitting. In a patient who is sitting fully upright, the zero point is simply at the fourth intercostal space at the sternum. As will be noted again below, a quick approximation of this location is half-way between the supra-sternal notch and the caudad xiphoid process.
Jugular venous pressure (JVP) estimation is a non-invasive surrogate for CVP used since 1930. However, as often performed, visual JVP has correlated poorly with CVP and many have trouble observing the neck veins, particularly in obese patients. The right internal jugular vein (IJ) is better for JVP assessment because it is in a more direct line with the right atrium.
The JVP is the vertical distance from the zero point to the highest level of distention in the right internal jugular vein . The peak occurs with expiration in spontaneously breathing adults, unless there is a positive Kussmaul sign.
Since other hemodynamic measurements are in mmHg, JVP is best expressed in mmHg by dividing the measured JVP height (in mm) by 13, which is the approximate density difference between mercury and whole blood. For example, a measured peak JVP of 130 mm is 10 mmHg.
JVP is a peak pressure and can never agree with a typically measured mean CVP. Normal IJ distension can only be seen above the clavicle in the sitting position of small adults. Most normal adults must be ≤ 45 degrees elevation to show distention and even then, the valve between the IJ and the subclavian vein (ScV) often blunts the distension. The lower limit of normal for peak right atrial pressure is about 6 mmHg. Converting this to mm of blood column height is 78 mm. Even in the fully supine position, the vertical height from the zero point at the mid-axillary line to the top of the clavicle is greater than 80 mm in most average sized adults. Thus, we can’t measure lower than normal in an average sized adult. With very small adults we might be able to measure a JVP lower than 6 mmHg.
One definition of the top of the JVP distention is in the longitudinal view where the vein collapses to a “beak”. Careful observation of an IJ in the transverse view can also identify the location in the neck where the IJ becomes mostly collapsed. Whether looking transverse or longitudinal, be sure to use light pressure so the IJ is not artificially compressed.
Peak JVP seems to always measure lower than peak CVP. The valve between the IJ and the ScV may be part of the underestimation, but other authors suggested that the cause is active venous tone that causes the IJ to collapse lower down than if the vein was only a “passive, floppy tube”. Clearly, peak JVP assessment requires a different cutoff from what we would use with a peak CVP. We think the best upper limit of normal for the peak JVP is about 10 mm Hg.
METHOD AND EXAMPLES
With the patient sitting on the exam table, classical technique starts with identifying the sternal angle which marks the location of the second rib. The image below shows the sternal angle marked and then the 2nd right intercostal space below the rib was marked.
Move down from the 2nd to the 4th intercostal space at the sternum and mark this location. This would be the zero point for a sitting patient.
In the picture below, the distance from the zero point to the top of the clavicle happens to be about 130 mm. If no IJ distention/pulsation was visible above the clavicle, the peak JVP would have been < 10 mmHg.
A SIMPLE SCREEN
For routine screening, eyeballing the location on the right sternum that is half way between the suprasternal notch and the xiphoid tip is an acceptable approximation of the 4th intercostal space and this is quicker than counting rib spaces. For any patient less than about 70 inches in height, the distance from this midpoint to the top of the clavicle in the sitting position is rarely over 130 mm and a mostly collapsed IJ in this position indicates a JVP < 10 mmHg.
For patients taller than 70 inches, the JVP may still be modestly elevated with no IJ distention above the clavicle. To evaluate these taller patients, the phlebostatic zero point at the mid-axillary line is needed, along with 30-45 degree patient elevation. Have the patient put his right hand on his head. Put your right little finger on the mid-point at the sternum and stretch your thumb out horizontally toward the side of the chest and put a mark at the mid-axillary line intersection.
DETAILS OF IJ ASSESSMENT
Place the linear probe transversely on top of the right clavicle, keeping it horizontal. Find the carotid artery, using CD if necessary. The IJ will usually be mostly collapsed, but still subtly varying, on top of (or lateral to) the carotid. To confirm the IJ ask the patient to do a modest Valsalva. The following clip shows a sitting patient with a normal, mostly collapsed IJ with subtle variation, followed at the end by a modest Valsalva that fully distended the vein.
In any body position, if the IJ distention is above the clavicle, find the top of the distention and measure the vertical height from the phlebostatic zero point and convert this to mmHg. When the IJ is mostly collapsed in a taller sitting patient, lower the patient to 30-45 degrees and repeat the IJ observation using the mid-axillary line zero point. Here is the above patient at about 30 degrees elevation. It is now only 100 mm from the zero phlebostatic point to the top of the clavicle. That means the peak JVP is less than 100/13 = about 8 mmHg. In a taller patient at 30 degree elevation, the top of the clavicle might be at the 130 mm (10 mmHg) level, which would be normal.
In any patient with elevated JVP, specifically watch the IJ while the patient takes moderate breaths. The JVP should fall with inspiration (there is a little time lag), unless there is a Kussmaul sign. The following clip was obtained from a patient with pericardial tamponade. Inspiration, with a dilated IJ, is at the very beginning of the clip and then the IJ collapsed as the patient exhaled.
Virtually any condition that compromises the right side of the heart and increases right atrial pressure can produce a Kussmaul sign. The sign is therefore a nice indicator of right sided disease, but not specific for an etiology.
The following clip shows a transverse view of the IJ in a normal patient at about 30 degrees. The IJ is more distended than in the upright patient, but it is still about half collapsed.
COLOR FLOW DOPPLER
CF was then applied to this transverse view with the probe fanned toward the heart. Red carotid flow was moving cephalad towards the probe, but the IJ flow was blue, coming down from the head. The orange color intermittently in the middle of the venous flow was aliasing as blood flow accelerated into the ScV each cycle.
Blood is always coming down the IJ from the head and accumulating at the IJ/ScV valve. Then, when the tricuspid valve opens during RV diastole and right atrial pressure falls, the IJ empties into the SVC. In cross section, we see this periodic filling and emptying as modest variation that may change with respiration.
Here is the same patient in longitudinal view. This clip was taken just below the IJ “beak” and the carotid is not in view. However, the IJ flow was still blue from above with some aliasing along the wall from higher velocity flow. There was no red flow from below.
The next clip shows an IJ that was mostly distended; it had subtle pulsation. If this was seen above the clavicle in in an average or greater height patient in the sitting position the JVP would be increased and could be measured as the direct height from the mid-sternum.
Here was the longitudinal view of this IJ showing the beak and the blue flow from above. Again, notice the aliasing near the wall. The lack of red flow from below indicates a competent valve without substantial tricuspid regurgitation.
With elevated JVP, the IJ/ScV valve may start to allow some flow through and red CF from below may be seen. Here was a normal IJ at 30 degrees with CF. Towards the end of the clip, a Valsalva maneuver was performed and a brief red flush towards the beak occured. This is flow coming from below.
With substantially elevated CVP, a large a-wave or v-wave may nicely transmit up the IJ. If the carotid pulsation (with or without color Doppler) is in view, an a-wave will occur slightly before the carotid flow and a v-wave occurs at the same time as the carotid pulsation.
With more severe TR, the IJ in the sitting position will be obviously distended and pulsating and CF is almost not needed to further evaluate. CF should show red flow coming from below. The top of the JVP is sought, but it may be up above the jaw in severe TR. Here is a transverse view, obtained in the upper neck without CD, from a patient with substantial TR.
And here is the same TR in longitudinal view showing the top where the beak appears.