From the Guidelines
Pulmonary vascular resistance (PVR) cut-off for pulmonary hypertension (PHTN) is 3 Wood units.
Definition of Pulmonary Hypertension
Pulmonary hypertension is defined as a mean pulmonary arterial pressure (mPAP) >20 mm Hg at rest, as measured by right heart catheterization [RHC] 1.
PVR Cut-off
A PVR of 3 Wood units is used to distinguish between precapillary and postcapillary pulmonary hypertension, with precapillary PH characterized by a PVR ≥3 Wood units and postcapillary PH characterized by a PVR <3 Wood units 1.
Diagnostic Criteria
The diagnostic criteria for pulmonary arterial hypertension (PAH) require both a mPAP greater than 25 mm Hg and a PVR greater than 3 Wood units 1.
- Key points to consider when diagnosing PAH include:
- mPAP >25 mm Hg
- PVR >3 Wood units
- PAWP ≤15 mm Hg
- It is essential to note that PAH remains a diagnosis of exclusion, and invasive hemodynamic studies are necessary to establish a correct diagnosis 1.
From the Research
Pulmonary Vascular Resistance Cut-off for Pulmonary Hypertension
The pulmonary vascular resistance (PVR) cut-off for pulmonary hypertension (PHTN) is a critical factor in diagnosing and managing the condition. According to the studies, the following points are relevant:
- The 2018 pulmonary hypertension definition includes a PVR cut-off of ≥3 Wood units (WU) to define precapillary PH 2.
- A study found that patients with precapillary PH and "borderline" PVR falling outside the current definition have adverse outcomes, and PVR ≥3 WU was the strongest predictor of death 2, 3.
- Another study suggested that PVR 2.2 to 3.0 WU, previously considered normal, appears to associate with elevated clinical risk 4.
- A review highlighted the importance of measuring PVR to separate pre-capillary from post-capillary PHT, with a goal of non-invasive assessment of PVR to streamline investigation and treatment 5.
- A recent study found that mild elevation of PVR (>2 WU) predicts mortality regardless of mean pulmonary artery pressure in mild interstitial lung disease, suggesting that PVR may be a more important factor than previously thought 6.