Jugular venous pressure

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The jugular venous pressure (JVP, sometimes referred to as jugular venous pulse) is the indirectly observed pressure over the venous system. It can be useful in the differentiation of different forms of heart and lung disease. Classically three upward deflections and two downward deflections have been described. the upward deflections are the "a" (atrial contraction), "c" (ventricular contraction and resulting bulging of tricuspid into the right atrium during isovolumic systole) and "v"= atrial venous filling. and the downward deflections of the wave are the "x"(the atrium relaxes and the tricuspid valve moves downward) and the "y" descent (filling of ventricle after tricuspid opening).

Certain wave form abnormalities, include "Cannon a-waves", which result when the atrium contracts against a closed tricuspid valve, due to complete heart block (3rd degree heart block), or even in ventricular tachycardia. Another abnormality, "c-v waves", can be a sign of tricuspid regurgitation.

An elevated JVP is the classic sign of venous hypertension (e.g. right-sided heart failure). JVP elevation can be visualized as jugular venous distension, whereby the JVP is visualized at a level of the neck that is higher than normal. The paradoxical increase of the JVP with inspiration (instead of the expected decrease) is referred to as the Kussmaul sign, and indicates impaired filling of the right ventricle. The differential diagnosis of Kussmaul's sign includes constrictive pericarditis, restrictive cardiomyopathy, pericardial effusion, and severe right-sided heart failure.

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[edit] Method

[edit] Visualization

The patient is positioned under 45°, and the filling level of the jugular vein determined. In healthy people, it is maximum several (3-4) centimetres above the sternal angle. A pen-light can aid in discerning the jugular filling level by providing tangential light.

The JVP is easiest to observe if one looks along the surface of the sternocleidomastoid muscle, as it is easier to appreciate the movement relative the neck when looking from the side (as opposed to looking at the surface at a 90 degree angle). Like judging the movement of an automobile from a distance, it is easier to see the movement of an automobile when it is crossing one's path at 90 degrees (i.e. moving left to right or right to left), as opposed to coming toward one.

Pulses in the JVP are rather hard to observe, but trained cardiologists do try to discern these as signs of the state of the right atrium.

[edit] Differentiation from the carotid pulse

The JVP and carotid pulse can be differentiated several ways:

  • multiphasic - the JVP "beats" twice (in quick succession) in the cardiac cycle. In other words, there are two waves in the JVP for each contraction-relaxation cycle by the heart. The first beat represents that atrial contraction (termed a) and second beat represents venous filling of the right atrium against a closed tricuspid valve (termed v) and not the commonly mistaken 'ventricular contraction'. The carotid artery only has one beat in the cardiac cycle.
  • non-palpable - the JVP cannot be palpated. If one feels a pulse in the neck, it is generally the common carotid artery.
  • occludable - the JVP can be stopped by occluding the internal jugular vein by lightly pressing against the neck.
  • varies with head-up-tilt (HUT) - the JVP varies with the angle of neck. If a person is standing their JVP appears to be lower on the neck (or may not be seen at all because it below the sternal angle). The carotid pulse's location does not vary with HUT.
  • varies with respiration - the JVP usually descreases with deep inspiration. Physiologically, this is a consequence of the Frank-Starling mechanism as inspiration decreases the thoracic pressure and increases blood movement into the heart (venous return), which a healthy heart moves into the pulmonary circulation.

[edit] JVP waveform

The jugular venous pulsation has a double waveform. The ‘a’ wave corresponds to atrial contraction and ends synchronously with the carotid artery pulse. The ‘c’ wave occurs when the ventricles begin to contract and is caused by bulging of the atrioventricular (AV) valves backwards towards the atria. The 'x' descent follows the 'c' wave and represents atrial relaxation and rapid filling due to low pressure. The ‘v’ wave is seen when the tricuspid valve is closed and is caused by a pressure increase in the atrium as the venous return fills the atria – with and just after the carotid pulse. The 'y' descent represents the rapid emptying of the atrium into the ventricle following the opening of the tricuspid valve. The absence of ‘a’ waves is a feature of atrial fibrillation.[citation needed] "Cannon a waves" or increased amplitude 'a' waves, are associated with AV dissociation (third degree heart block), when the atrium is contracting against a closed tricuspid valve.

[edit] Quantification

A classical method for quantifying the JVP was described by Borst & Molhuysen in 1952.[1] It has since been modified in various ways. A venous arc may be used to measure the JVP more accurately.

[edit] Hepato- or abdominojugular reflux

Main article: Abdominojugular test

Hepatojugular reflux, sometimes incorrectly referenced as a "reflex",[2] is an expanded form of the JVP measurement. By pressing on the liver (hepato-) for 15-30 seconds, venous blood is advanced into the circulation. The JVP increases slightly in a normal person. However, a marked, persistent increase of the JVP after checking for hepatojugular reflux can indicate right ventricular failure.

[edit] Interpretation

Causes of elevation:

An important use of the jugular venous pressure is to assess the central venous pressure in the absence of invasive measurements (e.g. with a central venous catheter, which is a tube inserted in the neck veins). A 1996 systematic review concluded that a high jugular venous pressure makes a high central venous pressure more likely, but does not significantly help confirm a low central venous pressure. The study also found that agreement between doctors on the jugular venous pressure can be poor.[3]

[edit] References

  1. ^ Borst J, Molhuysen J (1952). "Exact determination of the central venous pressure by a simple clinical method.". Lancet 2 (7): 304-9. PMID 14955978. 
  2. ^ Aronson J (1999). "Hepatojugular reflux". BMJ 318 (7192): 1172. PMID 10221938.  Free Full Text.
  3. ^ Cook DJ, Simel DL (1996). "The Rational Clinical Examination. Does this patient have abnormal central venous pressure?". JAMA 275 (8): 630–4. doi:10.1001/jama.275.8.630. PMID 8594245. 

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