Why ESC Uses PAWP Instead of PCWP
The European Society of Cardiology (ESC) uses "pulmonary artery wedge pressure" (PAWP) instead of "pulmonary capillary wedge pressure" (PCWP) because PAWP is the technically accurate term for what is actually measured during right heart catheterization—the pressure obtained when a balloon catheter is wedged in the pulmonary artery, which serves as a surrogate for left atrial pressure. 1
Technical Accuracy of Terminology
The term "pulmonary artery wedge pressure" more precisely describes the measurement technique:
- The catheter is advanced until it reaches the "PAWP position" in the pulmonary artery with the balloon inflated, not necessarily into the pulmonary capillaries themselves 1
- PAWP is explicitly defined as "a surrogate of LA pressure" in the ESC/ERS guidelines, emphasizing its functional role rather than anatomical location 1
- The measurement reflects left atrial pressure transmitted retrograde through the pulmonary veins when forward flow is occluded by the wedged balloon 1
Standardization Across Guidelines
The ESC/ERS 2015 guidelines consistently use PAWP throughout their hemodynamic definitions:
- Pre-capillary pulmonary hypertension is defined by PAWP ≤15 mmHg (not PCWP) 1
- All hemodynamic tables and diagnostic criteria reference PAWP as the standard parameter 1
- The guidelines specify that "PAWP should be recorded as the mean of three measurements" 1
Clinical Measurement Considerations
The ESC guidelines emphasize proper PAWP measurement technique:
- The balloon should be inflated in the right atrium and advanced until it reaches the PAWP position, avoiding repeated inflations/deflations in distal pulmonary arteries due to rupture risk 1
- Blood sampling with the balloon inflated in the wedge position can confirm accurate measurement (should show arterial-level oxygen saturation) 1
- PAWP may underestimate LV end-diastolic pressure in some patients, requiring clinical context for interpretation 1
Important Caveats
Research evidence reveals significant measurement challenges regardless of terminology used:
- End-expiratory PAWP measurements are more accurate than digitized mean values, with one study showing 27% of patients would be misclassified using digital averaging 2
- In patients with obesity or significant respirophasic variation, averaging PAWP throughout the respiratory cycle may be more physiologically appropriate than end-expiratory values alone 3
- When PAWP >15 mmHg is unexpected, direct measurement of LV end-diastolic pressure should be obtained to avoid misclassification, as 39% of patients with elevated PAWP may actually have normal LVEDP 4
The terminology shift to PAWP reflects technical precision about what is actually measured (wedge pressure in the pulmonary artery) rather than an assumption about where the catheter tip resides (pulmonary capillaries), while maintaining the same clinical utility as a surrogate for left atrial pressure. 1