How is Pulmonary Artery Wedge Pressure (PAWP) interpreted in clinical practice?

From the Guidelines

Pulmonary Artery Wedge Pressure (PAWP) is interpreted as an indirect measure of left atrial pressure, with a threshold of ≤15 mmHg indicating pre-capillary pulmonary hypertension and >15 mmHg indicating post-capillary pulmonary hypertension, as defined by the 2015 ESC/ERS guidelines 1. When interpreting PAWP, clinicians should consider it alongside other hemodynamic parameters such as cardiac output, pulmonary artery pressures, and systemic vascular resistance for a comprehensive assessment.

• PAWP measurement requires proper positioning of a pulmonary artery catheter (Swan-Ganz) with the balloon inflated to "wedge" in a small pulmonary artery branch.
• The pressure transmitted back through the pulmonary vasculature reflects left atrial pressure in the absence of pulmonary vascular disease.
• It's essential to note that PAWP may be falsely elevated in conditions like mitral stenosis or pulmonary veno-occlusive disease, and falsely normal in patients with pulmonary hypertension due to left heart disease who are receiving diuretics, as highlighted in the 2015 ESC/ERS guidelines 1.
• Accurate interpretation requires correlation with clinical context, including the patient's volume status, cardiac function, and respiratory status, as emphasized in the 2016 ESC/ERS guidelines 1.
• The interpretation of PAWP should be made in the context of the clinical picture and imaging, in particular echocardiography, to avoid misclassification of patients with an elevated PAWP when this is unexpected and may be inaccurate 1.

From the Research

Interpretation of Pulmonary Artery Wedge Pressure (PAWP)

PAWP is a measure used to assess the pressure in the left atrium and, by extension, the left ventricle during diastole. It is obtained through a procedure called pulmonary artery catheterization. The interpretation of PAWP is crucial in clinical practice for diagnosing and managing various cardiovascular conditions.

Normal and Abnormal Values

• A normal PAWP value typically ranges from 6 to 12 mmHg 2, 3, 4.
• Elevated PAWP values (>15 mmHg) may indicate postcapillary pulmonary hypertension or left heart disease 2.
• A PAWP value greater than 18 mmHg is often considered diagnostic for postcapillary pulmonary hypertension 2, 4.

Clinical Significance

• PAWP is used to differentiate between pre- and postcapillary pulmonary hypertension 2.
• An increase in PAWP ≥ 18 mmHg after a fluid challenge can help diagnose postcapillary pulmonary hypertension 2.
• High PAWP values (>18 mmHg) are common in patients with acute lung injury and acute respiratory distress syndrome (ALI/ARDS) and are associated with increased mortality 4.
• PAWP can be estimated using simple Doppler echocardiographic measurements, such as pulmonary artery systolic pressure (PASP) and cardiac output 5.

Relationship with Other Hemodynamic Parameters

• PAWP correlates moderately with PASP, and this correlation can be used to estimate PAWP in patients with normal left ventricular systolic function 5.
• The relationship between PAWP and pulmonary artery diastolic pressure (PADP) should be examined closely in critically ill patients, as a PAWP higher than PADP may indicate an erroneous measurement, while a PADP exceeding PAWP by 6.0 mmHg or more may indicate pulmonary hypertension and a poorer prognosis 6.

Limitations and Considerations

• PAWP measurements can be influenced by various factors, such as catheter position and pulmonary vascular resistance 6.
• The use of PAWP as a diagnostic tool requires careful consideration of these limitations and the clinical context in which it is being used.