Hepatic venous pressure gradient measurement: time to learn!

Portal hypertension is a clinical syndrome defined by a pathological increase in portal pressure. The development of cirrhosis of the liver is characterized by clinical manifestations related to portal hypertension like esophageal varices, ascites, bleeding, and encephalopathy. Direct measurement of portal pressure is invasive, inconvenient, and clinically impractical. Currently, the most commonly used parameter is the Hepatic Venous Pressure Gradient (HVPG), i.e., the difference between the wedged (WHVP) and the free hepatic venous pressures. HVPG represents the gradient between pressures in the portal vein and the intra-abdominal portion of inferior vena cava. When blood flow in a hepatic vein is stopped by a wedged catheter, the proximal static column of blood transmits the pressure from the preceding communicated vascular territory (hepatic sinusoids) to the catheter. Thus, WHVP reflects hepatic sinusoidal pressure and not the portal pressure itself. In the normal liver, due to pressure equilibration through interconnected sinusoids, wedged pressure is slightly lower than portal pressure, though this difference is clinically insignificant. In liver cirrhosis, the static column created by balloon inflation cannot be decompressed at the sinusoidal level due to disruption of the normal intersinusoidal communications; therefore, WHVP gives an accurate estimation of portal pressure in cirrhosis. The normal HVPG value is between 1 to 5 mmHg. Pressure higher than this defines the presence of portal hypertension, regardless of clinical evidence. HVPG >or= 10 mmHg (termed clinically significant portal hypertension) is predictive of the development of complications of cirrhosis, including death. HVPG above 12 mmHg is the threshold pressure for variceal rupture. The main advantages of HVPG are its simplicity, reproducibility, and safety. This review summarizes the technique of the HVPG measurement.