CVP

The CVP
This is the pressure recorded from the right atrium or superior vena cava 
It is representative of the filling pressure of the right side of the heart 

Normal is 8- 12 mmHg in a spontaneously breathing non-ventilated patient
recorded at the end of expiration

It is made up of many different waves:
a = atrial contraction (dominant in pulmonary HTN, TS, PS)
c = closing and bulging of the tricuspid valve (cannon in heart block) 
x = atrial relaxation (absent in AF, exaggerated in tamponade)
v = passive filling of atrium (dominant in TR)
y = opening of the tricuspid valve (sharp in severe TR, constrictive pericarditis. Slow in TR)

Raised CVP 
Fluid overload (although there is a poor relationship)
High PEEP settings (PEEP of 10cm H20 = CVP increase 3cm H20) 

Right ventricular failure
Tricuspid stenosis or regurgitation
Pericardial effusion or constrictive pericarditis
Superior vena caval obstruction

References
http://lifeinthefastlane.com/ccc/cvp-measurement/
Oxford Handbook of Critical Care