Global Coagulation Assessment in Portal Vein Thrombosis and Budd-Chiari Syndrome

Overview

Portal vein thrombosis is defined as partial or complete occlusion of the portal vein lumen by the blood clot or its replacement by multiple collateral vessels with the hepato-petal flow, known as 'portal cavernoma'. \[1,2\] Based on the published literature, 15-25% of patients with cirrhosis have portal vein thrombosis (PVT) \[3\], and 35-50% of patients with hepatocellular carcinoma (HCC) have malignant PVT \[4\] compared to 1-3.8 per 100,000 patients in the general population. \[5\] The reported cumulative incidence of PVT in patients of Child-Pugh A and B is 4.6% and 10.7% at 1 and 5 years respectively with higher incidence among those with decompensated disease or with an underlying hypercoagulable disorder. \[6\]. Similarly, the prevalence of PVT in compensated cirrhosis is around 1% which increases to 8 - 25% in liver transplant (LT) candidates and 40% in patients with hepatocellular carcinoma (HCC) \[7,8\]. Based on the published literature 7-9 % of all chronic liver disease patients have hepatic vein outflow tract obstruction (HVOTO) in the Indian population. \[9\] HVOTO is defined as obstruction to hepatic venous outflow at any site from the right atrium inlet to the small hepatic venules. The Budd-Chiari syndrome (BCS) results from occlusion of one or more hepatic veins (HV) and/or the inferior vena cava (IVC). In the West, the most common cause is HV occlusion by thrombosis. More recent Indian studies have however shown that isolated HV and combined IVC+HV obstruction are now more common. \[10\] In the post COVID-19 era, there has been great interest in the prothrombotic states associated with the SARS-Cov-2 virus infection, and the adverse effects of some vaccines. \[11\] With the availability of better molecular tests for hypercoagulable states, use of global coagulation tests (GCT) like rotational thromboelastometry (ROTEM), thromboelastography (TEG) and Sonoclot, use of therapeutic procedures like Transjugular intrahepatic portosystemic shunt (TIPS), availability of novel oral anticoagulants (NOAC), the natural course of disease can be changed with good outcomes. \[12\] Standard Coagulation tests (SCTs) like PT, aPTT, and platelet count are not predictive of bleeding or coagulation risk as they exclude the cellular elements of hemostasis and are unable to assess the effect of thrombomodulin and cannot assess the stage of the coagulation pathway which is affected. Global coagulation tests provide dynamic information on the coagulation pathway that is not available from conventional tests. \[13\]

Our proposed study is important for the following 4 reasons. 1. SCTs cannot be used to demonstrate the thrombomodulin mediated normal thrombin generation in patients with liver disease, so the monitoring of such patient using global coagulation tests can be validated. The use of point-of-care global coagulation tests like ROTEM and Sonoclot enables us to identify the true prothrombotic and hypocoagulable states which can be used to assess for increased clot strength, clot formation time, and indicate hyperfibrinolysis. The use of conventional tests like prothrombin time, partial thromboplastin time and INR cannot bolster the therapeutic strategy. 2. This study will also help to determine role of global coagulation tests rather than PT/INR /aPTT in monitoring the dose and response of anticoagulants like vitamin K antagonists and novel oral anticoagulants (NOAC) in patients who are on therapeutic anticoagulation for HVOTO/PVT. 3. This study will also help to determine the prevalence and role of CALR, JAK2V617F, factor V Leiden mutations in patients with PVT and HVOTO in our population. 4. We will also be prospectively assessing the rate of thrombophilia complications in the Post COVID-19 era, and the study will generate information regarding new incidence of PVT/HVOTO in those exposed to COVID-19. Therefore, the current study is the need of the hour, as we intend to assess the relevance of PVT and outcomes, test the genetic predisposition of Indian patients to hyper coagulable states, develop anticoagulation algorithms using NOAC, and determine the true burden on disease in India.