| Definition | PH occurring in the context of PHT, with or without intrinsic liver disease | Hypoxaemia due to IPVDs in patients with chronic liver disease and/or PHT |
| Prevalence (in cirrhotic patients) | PoPH, less common than HPS, is present in ~0.7% of patients with cirrhosis, 2% of patients with PHT and 5%–15% of PH cases | Affects ~30% of patients with cirrhosis; range: 4%–47% |
| Pathophysiological mechanisms | Pulmonary vasoconstriction, medial hypertrophy, intimal fibrosis and plexiform lesions due to circulating vasoactive mediators | Diffuse capillary vasodilation, increased NO production, angiogenesis, and impaired alveolar-capillary oxygen exchange |
| Diagnostic criteria | PHT, mPAP >20 mmHg, PVR >2 Wood units, PCWP ≤15 mmHg (confirmed by RHC) | Chronic liver disease or PHT, A-a gradient ≥15 mmHg (or ≥20 mmHg if ≥65 years), IPVD on CE-TTE |
| Clinical presentation | Exertional dyspnoea, fatigue and signs of right heart strain | Platypnoea, orthodeoxia, cyanosis, digital clubbing and prominent hypoxaemia |
| ECG findings | RBBB, rightward axis and RV hypertrophy | None |
| Key imaging/testing modalities | Transthoracic Doppler echocardiography followed by RHC | CE-TTE and arterial blood gas testing |
| Therapeutic strategies | Pulmonary vasodilators (PDE5 inhibitors, prostacyclin analogues, and endothelin receptor antagonists), oxygen and avoid TIPS | No proven medical therapy; supplemental oxygen and LT are mainstays. TIPS may have a transient benefit |
| LT implications | Considered for LT if mPAP is <35 mmHg or medically optimised. Perioperative mortality risk is high if mPAP is ≥45 mmHg | Indicated for LT if PaO2 is <60 mmHg. Post-transplant hypoxaemia typically resolves. Long-term prognosis is excellent |
| Prognosis | Variable. Five-year post-LT survival ranges from 63% to 67%; high early mortality risk, especially if mPAP ≥45 mmHg. Ongoing medical therapy may be required | Favourable after LT. Five-year survival ~76%, comparable to non-HPS patients; hypoxaemia typically resolves completely |
