Puzzling out PAC Pressures

PDP and PAOP are elevated in tandem, with only a mild increase in RAP.

This pattern is consistent with an elevated left atrial pressure (LAP) usually due to left ventricular failure (elevated LV EDP) or mitral valve disease (rarely an atrial myxoma).

A useful rule of thumb is that the PAOP should be no more than 2 mmHg higher than RAP. PAOP reflects LAP – and is increased in the presence of either an elevated LV EDP from LV failure or mitral valve disease.

There is an isolated elevation in PDP.

This pattern is consistent with pulmonary vascular disease or pulmonary hypertension. Underlying diagnoses may include conditions such as ARDS, COPD, PE or pneumonia.

A useful rule of thumb is that the PDP should be no more than 2 mmHg higher than PAOP (different sources suggest 1-5 mmHg), unless there is pulmonary vascular disease/ pulmonary hypertension.

All 3 values are elevated in unison.

This pattern is consistent with fluid overload.

The rule of thumb to remember is that ventricles don’t usually fail equally, biventricular failure is unlikely to cause this pattern. Early pericardial tamponade is an alternative explanation.

PDP and RAP are elevated.

This pattern is consistent with cor pulmonale, i.e. right ventricular failure due to pulmonary hypertension.

The rule of thumb is that RAP is always less than PAOP unless there is right ventricular failure.

All 3 values are markedly elevated in unison.

This pattern is consistent with pericardial tamponade.

As for Q3, ventricles tend not to fail equally. The additional rule of thumb is that fluid alone rarely causes pressures >20 mmHg.

This pattern doesn’t make physiological sense!

The PAOP should be less that PDP. Thus the PAOP measurement may be inaccurate, it might represent mean PA pressure if there is a damped PA pressure waveform.

This is normal!

All the values are within standard reference ranges and the normal pattern is present: PAOP <2 mmHg higher than RAP and PDP <2 mmHg higher than PAOP.

This normal, but with an artefactually elevated RAP due to fluid infusion through the RA line.

As a rule of thumb, RAP is only higher than PDP due to a measurement error or artefact.

The PAOP is elevated, with a more marked increase in PDP. The RAP is also mildly elevated.

This is consistent with a combination of left ventricular failure and pulmonary hypertension.

This is most commonly in elderly patients with acute or chronic lung disease, or chronic left ventricular failure causing pulmonary hypertension.

PDP is elevated, and RAP is mildly elevated.

This is abnormal but the underlying diagnosis is uncertain, it could be PE, a milder form of Q4 or if the actual PAOP is elevated the same as Q9.

When unable to wedge the PA catheter, if air returns to the syringe then the catheter is probably not advanced far enough into the pulmonary arterial tree. If air does not return to the syringe, then the balloon is probably ruptured.