Hemodynamic Parameters in Pulmonary Veno-Occlusive Disease
Pulmonary veno-occlusive disease (PVOD) presents with precapillary pulmonary hypertension hemodynamics: mPAP ≥25 mmHg, PAOP (PAWP) ≤15 mmHg, and elevated transpulmonary gradient (TPG), despite the pathology being in the post-capillary venules. 1
Specific Hemodynamic Values
Mean Pulmonary Artery Pressure (mPAP)
- Elevated mPAP ≥25 mmHg is required for diagnosis of pulmonary hypertension 1
- In PVOD cohorts, systolic PAP values around 78 mmHg have been reported (lower than other PAH subtypes at 98 mmHg) 2
Pulmonary Artery Occlusion Pressure (PAOP/PAWP)
- PAOP ≤15 mmHg defines the precapillary pattern 1
- Specific case reports document normal PAWP of 10 mmHg in confirmed PVOD 3
- This normal or low-normal PAWP is paradoxical given the venular pathology but reflects the inability to accurately measure true left atrial pressure due to venular obstruction
Transpulmonary Gradient (TPG)
- Elevated TPG (mPAP - PAWP) results from the combination of elevated mPAP and normal/low PAWP
- The diastolic pressure gradient (DPG) and pulmonary vascular resistance (PVR) are also elevated
Additional Hemodynamic Features
Pulmonary vascular resistance is markedly elevated, typically:
- PVR >3 Wood Units (required for precapillary PH definition) 1
- Case series report PVR around 5.93-10.6 Wood Units 3, 2
Cardiac index is often severely reduced:
- Values as low as 1.75 L/min/m² have been documented 4
Right atrial pressure may be lower than other PAH forms:
- 6.5 mmHg in PVOD vs 11.5 mmHg in other PAH 2
Critical Diagnostic Pitfall
The major diagnostic challenge is that PVOD mimics idiopathic PAH hemodynamically despite having fundamentally different pathophysiology (venular vs arterial disease). 1 The PAWP remains normal because the balloon occlusion occurs proximal to the obstructed venules, failing to reflect true left atrial pressure. This is why PVOD is classified under Group 1 (PAH) in the clinical classification, specifically as subgroup 1.2. 1
PVOD is distinguished from other PAH by clinical and radiographic features rather than hemodynamics alone: characteristic HRCT findings (septal lines, centrilobular ground-glass opacities, lymphadenopathy), severely reduced DLCO (often <35% predicted), and genetic testing for EIF2AK4 mutations are essential for diagnosis. 5, 4
The normal PAWP in PVOD creates a dangerous treatment scenario: aggressive pulmonary vasodilator therapy can precipitate acute pulmonary edema because the venular obstruction prevents adequate drainage, making early recognition critical before initiating standard PAH therapies. 5, 4