What is the role of cardiac pressures in pulmonary artery catheterization (PAC)?

Updated: Dec 22, 2017
  • Author: Bojan Paunovic, MD; Chief Editor: Karlheinz Peter, MD, PhD  more...
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Right- and left-sided heart pressure waveforms share many physiologic similarities, but, in the healthy individual, the waves are of different magnitudes.

Right-sided pressures

The central venous pressure (CVP) and right atrial pressure (RAP) are nearly equal to the diastolic RV pressure in the absence of heart or lung disease (see image below).

Central venous pressure (CVP) measured in superior Central venous pressure (CVP) measured in superior vena cava (SVC) is identical to right atrial pressure (RAP).

The mean CVP and RAP normally range from 0-5 mm Hg, and vary as intrathoracic pressure changes with respiration (see image below).

Respiratory variation is easily identified on the Respiratory variation is easily identified on the right atrial waveform.

RA contraction creates pressure changes, which are influenced strongly by the patient's volume status. Atrial contraction produces an increase in pressure called the A wave. The C wave is a small convexity noted on the initial descent of the A wave and is thought to be secondary to closure of the tricuspid valve. The initial descent after the A wave is called the X descent. This decline in RAP is secondary to RA relaxation and downward movement of the tricuspid valve. Following this is the V wave, which is somewhat smaller than the A wave, and reflects RA filling during ventricular systole. The Y descent occurs after the V wave and represents rapid filling of the RV after opening of the tricuspid valve (see image below).

Various waveforms of central venous pressure (CVP) Various waveforms of central venous pressure (CVP) monitoring are shown here.

CVP is most commonly elevated in the setting of biventricular heart failure. Other causes of RAP elevation are tricuspid regurgitation or stenosis, pulmonary hypertension, volume overload, constrictive pericarditis, and cardiac tamponade. Large, so-called cannon A waves occur when the RA contracts against a closed tricuspid valve. Cannon A waves are detected in certain cardiac rhythm disturbances, including junctional rhythms and ventricular tachycardia, and in some patients with ventricular pacemakers. Large V waves may occur in the presence of tricuspid regurgitation, with their magnitude affected by the size and compliance of the RA.

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