This chapter is relevant to Section G7(iii) of the 2017 CICM Primary Syllabus, which asks the exam candidate to "describe the invasive and non-invasive measurement of blood pressure, including limitations and potential sources of error". The college examiners have never expected their candidates to analyse any CVP waveforms and so the time-poor exam candidate can safely ignore this page and probably all the other pages in this CVP section.
Anatomy of the CVP waveform
- a is for atrium… this is the right atrial contraction.
- It correlates with the P wave on the ECG.
- It disappears with atrial fibrillation
- c is for cusp… this is the cusp of the tricuspid valve, protruding backwards through the atrium, as the right ventricle begins to contract.
- It correlates with the end of the QRS complex on the ECG
- This is the movement of the right ventricle, which descends as it contracts
- The downward movement decreases the pressure in the right atrium. At this stage, there is also atrial diastolic relaxation, which further decreases the right atrial pressure.
- It happens before the T wave on the ECG
- As blood fills the right atrium, it hits the tricuspid valve and this is the back-pressure wave
- It happens after the T wave on the ECG
- It also gives an impression of tricuspid competence.
- A huge V wave is suggestive of tricuspid regurgitation, as it represents blood flowing back out of the contracting right ventricle; in this situation the V wave would be the most prominent wave, and would reach right ventricular systolic pressure ( ~ 30mmHg)
- This is a pressure decrease caused by the tricuspid valve opening in early ventricular diastole.
- This happens before the P wave of the ECG
- A loss of y-descent suggests tamponade; it means there is restriction to right ventricular filling.