CVP trace: interpretation
Pretest
Match the alphabetic statements with the numerical s
A. Canon waves
B. A wave
C. Y descent
D. A volume challenge of 250-500 ml crystalloid causing an increase in CVP that is not sustained for more than 10 minutes
with
1. hypovolaemia
2. junctional arrhythmias
3. atrial emptying
4. atrial contraction
Keyword
The central venous pressure (CVP) is measured with the patient lying flat; it is expressed in cmH2O above a point level with the right atrium.
The normal value is 0-8 cmH2O. Clinically, it is useful as an indication of right ventricular preload.
A volume challenge of 250-500 ml crystalloid causing an increase in CVP that is not sustained for more than 10 minutes suggests hypovolaemia, for example. Serial readings (i.e. the trend of CVP measurements) are thus far more useful than single readings.
Raised CVP
Increased intrathoracic pressure
Impaired cardiac function (failure, tamponade. Only useful for information regarding the right side of the heart).
Hypervolaemia
Superior vena cava obstruction
Decreased CVP
Hypovolaemia
Reduced intrathoracic pressure (e.g. inspiration)
from
http://frca.co.uk/SearchRender.aspx?DocId=992&Index=D%3a%5cdtSearch%5cUserData%5cAUK&HitCount=5&hits=2a+61+76+81+9c+
A wave - due to atrial contraction. Absent in atrial fibrillation. Enlarged in tricuspid stenosis, pulmonary stenosis and pulmonary hypertension.
C wave - due to bulging of tricuspid valve into the right atrium or possibly transmitted pulsations from the carotid artery.
X descent - due to atrial relaxation
V wave - due to the rise in atrial pressure before the tricuspid valve opens. Enlarged in tricuspid regurgitation.
Y descent - due to atrial emptying as blood enters the ventricle.
Canon waves - large waves not corresponding to a, v or c waves. Due to complete heart block or junctional arrhythmias.
From http://www.anaesthesiauk.com/article.aspx?articleid=100036
Post test
Match
A. Canon waves
B. A wave
C. Y descent
D. A volume challenge of 250-500 ml crystalloid causing an increase in CVP that is not sustained for more than 10 minutes
with
1. hypovolaemia
2. junctional arrhythmias
3. atrial emptying
4. atrial contraction
Answer
1.D
2. A
3. C
4. B