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 basic and important for many patients. Second, the JVP should be evaluated first in many patients having cardiac POCUS. Third, it nicely uses the color Doppler (CD) 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 sitting fully upright, the zero point is simply at the fourth intercostal space.
Jugular venous pressure (JVP) estimation is a non-invasive surrogate for RAP/CVP used since 1930. However, as often performed, visualized JVP has correlated poorly with RAP/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.
Many have defended the view that the zero phlebostatic point for JVP measurement should logically be the same point as used for RAP/CVP measurement. However, some wanted to simplify JVP measurement and suggested using the sternal angle (angle of Louis) as the beginning point for JVP height, coupled with an added 5 cm as the fixed distance down to the right atrium. However, the distance from the middle of the right atrium to the sternal angle varies considerably based on patient size and degree of body elevation and a fixed 5 cm is wrong for many patients.
The JVP is the vertical distance from the zero point to the highest level in the right internal jugular vein at which distention (almost always with some pulsation) can be identified. The peak occurs with expiration in spontaneously breathing adults, unless there is a positive Kussmaul sign. Thus, JVP is a peak pressure and not a mean pressure as usually reported for RAP/CVP. JVP can never agree with a typically measured CVP! Normal IJ distension/pulsation can only be seen above the clavicle in the sitting position of very small adults. Most adults with normal RAP/CVP must be ≤ 45 degrees elevation to show distention/pulsation and even then, the valve between the IJ and the subclavian vein (ScV) often blunts the distension. JVP may not even be visible above the clavicle in supine adults with low normal RAP/CVP. Thus, JVP is unreliable for diagnosing below normal RAP/CVP. As JVP increases, patients need to be increasingly elevated to bring the top of the pulsation down below the angle of the mandible. In patients with the highest JVP, the distention/pulsation may be above the jaw even in the sitting position.
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 Hg and whole blood. A measured peak JVP of 130 mm is 10 mmHg.
POCUS was first described to identify the top of the JVP pulsation in 2000. Later reports, usually in supine ICU patients, used several different cross sectional measurements and ratios to correlate with CVP and were only roughly successful. However, more recent studies returned to a classic approach of finding the top of the JVP pulsation using POCUS in more upright patients. The clearest definition of the top is in the longitudinal view where the vein collapses to a “beak”. However, careful observation of a distended 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.
Even using the classic phlebostatic zero point and a clear definition of the JVP top, JVP seems to measure lower than peak RAP/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 at a lower point than if the vein was only a “passive, floppy tube”. We think the best upper limit of normal for the peak JVP is about 10 mm Hg. We may miss some mildly elevated CVP patients, but don’t want to overcall this abnormality.
DETAILED METHOD AND EXAMPLES
With the patient sitting at the end of the exam table, identify the sternal angle. The second rib joins the sternum at this location. The image below shows the sternal angle marked and then the 2nd right intercostal space was marked.
Move down successively on the right 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.
THE SIMPLE APPROACH
For any patient less than about 70 inches in height, the distance from the 4th intercostal space to the top of the clavicle in the sitting position is rarely much over 130 mm and a mostly collapsed IJ in this position indicates a non-elevated JVP and the exam would be done.
For taller patients, a modestly elevated JVP could still be below the clavicle in the sitting position and an additional zero point is needed Have the patient put his right hand on his head. Put your right little finger on the 4th intercostal space 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. This is the zero phlebostatic point for a body position less than vertical.
Place the linear probe (VENOUS exam type, indicator examiner left), 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 pulsation, followed at the end by a modest Valsalva that fully distends the vein.
When the IJ is mostly collapsed in the sitting position in taller adults, and elevated JVP is still possible, a 30-45 degree elevation assessment would be needed to be sure the JVP was < 10 mmHg. 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 cannot be greater than 100/13 = about 8 mmHg, which is clearly normal. In a taller patient, the top of the clavicle might be at the 130 mm (10 mmHg) level and would be at the upper limit of normal.
In any patient with possibly 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.
CD was then applied to this transverse view with the probe angling slightly toward the chest. 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 and right atrial pressure falls, the IJ empties into the SVC. In cross section, we see this periodic filling and emptying as modest pulsation that may change with respiration. The normal IJ collapse is at a slightly different time than the carotid pulsation.
The longitudinal view of the IJ can show a “beak”, representing the top of the IJ, and pulsation. Here is the same patient in longitudinal view. Notice the angle of the CD sector box was tilted +20, so flow from below toward the probe was more clearly red. 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 4th intercostal space.
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 tricuspid regurgitation.
When JVP is elevated distention and the beak will move up the neck. A tape measure is used to measure the vertical height from the zero phlebostatic point to the top of the JVP. Elevated JVP is always best measured with a fully sitting patient.
With elevated JVP, the IJ/ScV valve may start to allow some flow through and red CD flow from below may be seen. Here was a normal IJ at 30 degrees with CD. Towards the end of the clip, a Valsalva maneuver was performed and a brief red flush towards the beak occurs. This is flow coming from below.
With substantially elevated RAP/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. Alternatively, palpate the left carotid to time the red flow from below. A v-wave will occur with the carotid while an a-wave will occur just before the carotid pulse.
With more severe TR, the IJ in the sitting position will be obviously distended and pulsating and CD is almost not needed to further evaluate. Color Doppler should show red flow coming from below. The top of the JVP is sought, but there may not be one 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.