Invasive diagnosis of portal hypertension in cirrhosis: a critical evaluation of the hepatic venous pressure gradient measurement

Portal hypertension is defined by an increased pressure gradient between the portal vein and the inferior vena cava (N < 5 mmHg). The most commonly used technique to assess the severity of portal hypertension is the catheterization of one hepatic vein with measurement of pressures in a free position and in a wedged position using preferably a balloon catheter. The hepatic venous pressure gradient is calculated by the difference between both pressures. In most cirrhotic processes, venous pressure gradient gives a good evaluation of portal hypertension however, portal vein pressure can be higher than wedged hepatic venous pressure, particularly in presence of an increased pre-sinusoidal resistance. In such cases, a direct access to portal vein might be needed to assess the severity of portal hypertension. For an accurate interpretation of the hepatic venous pressure gradient, several strict criteria must be followed; otherwise the validity of measurements might be seriously questioned. Hepatic venous pressure gradient has been used as a prognostic marker of portal hypertension, particularly for the occurrence of bleeding from gastrophageal varices which almost never occur below a threshold value of 12 mmHg. However, the prognostic value of the hepatic venous pressure gradient for survival is still a controversial matter On the other hand, the use of hepatic venous pressure gradient has been proposed to monitor the pharmacological treatment of portal hypertension and it is generally accepted that reaching a same threshold value of 12 mmHg should almost completely abolish the risk of first or recurrent variceal bleeding. A large number of studies have also reported that a 20% hepatic venous pressure gradient decrease should be considered as a significant response to therapy, the risk of the first or recurrent bleeding being significantly reduced in responders. But again there are conflicting results.