How does the Hepatic Venous Pressure Gradient (HVPG), measured as the difference between wedge hepatic venous pressure and free hepatic venous pressure, reflect portal pressure in patients with cirrhosis?

How HVPG Reflects Portal Pressure in Cirrhosis

The hepatic venous pressure gradient (HVPG), calculated as wedged hepatic venous pressure minus free hepatic venous pressure, serves as an accurate surrogate measure of sinusoidal pressure and portal pressure specifically in sinusoidal portal hypertension (cirrhosis from alcohol, HCV, NASH), but does NOT reliably reflect portal pressure in prehepatic, presinusoidal, or posthepatic causes of portal hypertension. 1

The Physiologic Basis

When the balloon catheter is wedged in the hepatic vein, it creates a static column of blood that transmits pressure from the hepatic sinusoids back to the catheter. 2 This wedged pressure reflects sinusoidal pressure because:

• In normal liver, pressure equilibrates through interconnected sinusoids, making wedged pressure slightly lower than portal pressure (clinically insignificant difference) 2
• In cirrhosis, the static column cannot decompress at the sinusoidal level due to disrupted intersinusoidal communications, therefore WHVP accurately estimates portal pressure 2
• The free hepatic venous pressure (FHVP) measured at the hepatic vein-IVC junction represents the "downstream" pressure 1
• The gradient (HVPG = WHVP - FHVP) therefore estimates the pressure difference between the portal vein and inferior vena cava 1, 2

Critical Limitations by Etiology

HVPG only provides useful data in sinusoidal portal hypertension. The following table from AASLD guidelines clarifies when HVPG is accurate: 1

Sinusoidal Portal Hypertension (HVPG Accurate):

• Cirrhosis from alcohol, HCV, NASH: WHVP elevated, FHVP normal, HVPG elevated 1

HVPG NOT Accurate:

• Prehepatic (portal vein thrombosis): All measurements normal 1
• Presinusoidal (cholestatic cirrhosis, schistosomiasis, idiopathic portal hypertension): All measurements normal (though in advanced stages HVPG may increase) 1
• Postsinusoidal (sinusoidal obstruction syndrome): WHVP elevated, FHVP normal, but HVPG normal 1
• Posthepatic (right heart failure): WHVP elevated, FHVP elevated, HVPG normal 1

Important Caveats in Alcoholic Cirrhosis

Recent evidence shows HVPG may significantly underestimate portal pressure in alcoholic cirrhosis, particularly when hepatic collaterals are present. 3 In a 2023 study:

• The correlation between HVPG and directly measured portal pressure gradient (PPG) was poor (r=0.201, R²=0.040) 3
• When hepatic collaterals were present (19.4% of cases), HVPG dramatically underestimated PPG (9.86 vs 25.94 mmHg, P<0.001) 3
• Even without collaterals, wedged pressure was lower than portal pressure (30.65 vs 33.25 mmHg, P=0.002) 3

This contradicts the traditional teaching and suggests direct portal pressure measurement may be necessary in alcoholic cirrhosis when precise values are clinically critical. 3

Clinical Thresholds and Their Significance

Normal HVPG: 1-5 mmHg 1, 2

Portal hypertension: HVPG >5 mmHg 1, 4

Clinically significant portal hypertension (CSPH): HVPG ≥10 mmHg - above this threshold, complications (varices, ascites, clinical decompensation) become likely 1, 5, 4

Variceal bleeding threshold: HVPG >12 mmHg - identifies patients at risk for variceal hemorrhage 1, 2

High mortality threshold: HVPG ≥16 mmHg - independently associated with higher mortality in both compensated and decompensated cirrhosis 1, 5

Acute bleeding failure threshold: HVPG ≥20 mmHg - predicts failure to control bleeding, early rebleeding, and death during acute variceal hemorrhage 1

Prognostic Value

Each 1-mmHg increase in HVPG predicts a 3% increase in risk of death in cirrhotic patients awaiting liver transplantation (median follow-up 19 months). 1

Therapeutic response monitoring: Reducing HVPG to ≤12 mmHg or by ≥20% from baseline is associated with protection from variceal hemorrhage. 1, 5