How is the Hepatic Venous Pressure Gradient (HVPG) measured?

Hepatic Venous Pressure Gradient (HVPG) Measurement Technique

The hepatic venous pressure gradient (HVPG) is measured through catheterization of the hepatic vein using a balloon catheter, calculating the difference between the wedged (occluded) hepatic venous pressure and the free hepatic venous pressure. 1

Standard Measurement Procedure

Preparation

• Patient positioned supine, preferably under general anesthesia to minimize movement 1
• Prophylactic antibiotics administered (e.g., ciprofloxacin or cefazolin) 1
• Compact manometer leveled at the midaxillary line/level of the right heart 1

Vascular Access

• Under local anesthesia and ultrasound guidance, a catheter introducer sheath is placed in the right internal jugular vein 2
• Using fluoroscopic guidance, a balloon catheter is advanced into the inferior vena cava (IVC) and then into a large hepatic vein 2

Pressure Measurements

1. Free Hepatic Venous Pressure (FHVP):

   • Measured with the catheter tip free in the hepatic vein
   • Multiple readings taken (at least 3) and averaged 2

2. Wedged Hepatic Venous Pressure (WHVP):

   • Balloon inflated to occlude the hepatic vein
   • Correct wedge position confirmed by injecting contrast media
   • Multiple readings taken (at least 3) and averaged 2

3. HVPG Calculation:

   • HVPG = WHVP - FHVP 1
   • Normal HVPG is 3-5 mmHg 1, 3

Additional Measurements

• IVC pressure at the same level as hepatic vein measurements
• Right atrial pressure 2

Clinical Significance of HVPG Values

• HVPG > 5 mmHg: Portal hypertension present 1, 3
• HVPG ≥ 10 mmHg: Clinically significant portal hypertension (CSPH) 1, 3
• HVPG > 12 mmHg: Increased risk of variceal bleeding 1, 3
• HVPG > 16 mmHg: Higher risk of mortality 1
• HVPG ≥ 20 mmHg: Predicts failure to control bleeding, early rebleeding, and death during acute variceal hemorrhage 1

Important Technical Considerations

• Ensure proper calibration of the external pressure transducer before measurements 2
• Take triplicate readings of both WHVP and FHVP for accuracy 2
• For accurate PPG (portal pressure gradient) calculation, measurement of free hepatic or IVC pressure at the shunt outflow should be used 1
• WHVP reflects hepatic sinusoidal pressure, not direct portal pressure 4

Limitations and Caveats

• HVPG measurements have limited utility in prehepatic or presinusoidal portal hypertension 1
• In normal liver, wedged pressure is slightly lower than portal pressure, though this difference is clinically insignificant 4
• In cirrhosis, WHVP gives an accurate estimation of portal pressure due to disruption of normal intersinusoidal communications 4
• Despite its clinical value, HVPG measurement requires specific expertise, is invasive, relatively expensive, and not widely available 1, 3

Alternative Approaches

• EUS-guided PPG (EUS-PPG) is a novel technique that allows direct measurement of the hepatic vein portal pressure gradient 1
• EUS-PPG is performed using a linear echoendoscope with a 25-gauge needle via a transgastric approach 1
• Noninvasive tests (elastography techniques) are being developed but currently cannot fully replace HVPG measurement 1, 5

The HVPG measurement remains the gold standard for assessing portal pressure and has important diagnostic and prognostic implications in patients with chronic liver disease, particularly for risk stratification and management decisions related to portal hypertension complications.