Abnormal Central Venous Pressure Waveform Patterns

There are distinct CVP waveform patterns associated with atrial fibrillation, junctional rhythms, tricuspid valve disease and reduced right ventricular compliance.

Loss of a-waves: atrial fibrillation

CVP loss of a waves in AF

Because the atrial contraction is responsible for the a wave, loss of atrial contraction results in a missing a wave. Very simple. The baseline in the picture is undulating to represent AF, but in reality this may not be visible because the atrium is contracting in such a feeble and disorganised manner that its activity may not produce any pressure waves whatsoever.

Cannon a-waves: junctional rhythm

CVP Cannon a waves

In a junctional rhythm, the atrial contraction occurs at the same time as the ventricular contraction, which results in a fusion of the a and c waves.

Additonally, there are circumstances when the atrium contracts against a closed tricuspid valve, with the force of this contraction being reflected off the valve leaflets, forming a cannon a-wave.

This happens with retrograde conduction of ventricular action potentials. It can also be seen in complete heart block, where much of the the time the atrium contracts against a closed or partially closed tricuspid valve. Lastly, ventricular tachycardias are typically events where the atrium depolarises by retrograde conduction, so any atrial activity happens during ventricular systole, and generates a cannon a-wave,

Thus the causes of cannon a-waves are:

  • retrograde conduction of ventricular depolarisation:
    • ventricular tachycardia
    • junctional rhythm
  • Asynchronous atrial activity
    • complete heart block

Regurgitant cv waves: tricuspid regurgitation

CVP fused c and v waves

In tricuspid regurgitation, the backflow of blood out of the right ventricle obliterates the normal x descent. The c wave becomes accentuated and fuses with the v wave, as both are the results of right ventricular contraction (and the v wave peak pressure is often the same as the right ventricular peak systolic pressure).

Prominent a waves: tricuspid stenosis, or reduced right ventricular compliance

CVP in tricuspid stenosis

Tricuspid stenosis produces a large a-wave because of increased resistance to flow from the atrium to the ventricle. The y wave is attenuated (i.e. of longer duration and of lower amplitude) because the right atrial filling is slow and lazy, without a pronounced change in pressure which would normally occur.

This can also happen in pericardial disease (or anything which results in decreased myocardial compliance), the result of which is a restriction of filling for all the chambers.

Of courser, if tricuspid stenosiscan cause these waves, then any loss of compliance ahead of the tricuspid valve can also do this. In this fashion one may have prominent a-waves in the presence of a reasonably normal tricuspid valve, with pulmonary stenosis or pulmonary hypertension.

Thus, the causes of dominant a-waves are

  • Tricuspid stenosis
  • Pulmonary stenosis
  • Pulmonary hypertension

Bifid CVP waveform: pericardial constriction

CVP in pericardial constriction

In pericardial constriction, the CVP will be raised, and the x and y descent is steep and abrupt. This contrasts with cardiac tamponade where the y-descent is prolonged.

References

Most of this material can be found in From and Soni’s” Oh's Intensive Care Manual”, 6th Edition, as well as the CVC section from The ICU Book by Paul L Merino (3rd edition, 2007)

Additionally, I have made use of the amazing Essentials of Critical Care, 8th ed.(ch.3 - Monitoring in the ICU).

For those willing to pay for it, there is a good UpToDate article on this.

JAL Pittman et al, Arterial and Central Venous Pressure Monitoring, Int Anesthesiol Clin. 2004 Winter;42(1):13-30.