Comparative Analysis of Splanchnic Vein Thrombosis Prevalence and Clinical Relevance Versus Other Thromboses in Hispanic Patients with Myeloproliferative Neoplasms
Authors: Zalapa Jessica , Tuna Aguilar Elena Juventina , Ceja Ramirez Laura , Rangel-Patiño Juan , Vargas Ruiz Angel Gabriel , Pacheco Serrano Martin 
Published: December 2024

Introduction
Myeloproliferative neoplasms (MPN) are clonal disorders characterized by the proliferation of myeloid cells, associated with an increased risk of thrombosis. Although rare, splanchnic vein thrombosis (SVT) is primarily caused by MPN. SVT-related complications, such as portal hypertension and chronic liver disease, worsen clinical outcomes and quality of life. The median age at MPN diagnosis in patients with SVT differs from those with MPN and thrombosis at other sites (non-SVT). Therefore, this study aims to compare the characteristics of patients with SVT to those of patients with non-SVT and to recognize the clinical relevance of their complications.
Methods
This retrospective cohort study was conducted at a single reference center in Mexico City. It included adult patients over 18 years diagnosed with Philadelphia-negative MPN and thrombosis from January 2000 to December 2023.
Thrombosis may have occurred either before, concurrently with, or after the diagnosis of MPN. A comparative analysis of baseline characteristics was performed between patients with SVT and other thrombosis sites, using Student's t-test or Mann-Whitney U test for continuous variables, and the Chi-square test or Fisher's exact tests for categorical variables. A univariate analysis was performed to determine the factors associated with SVT. For patients with SVT, associated complications were evaluated.
Results
A total of 193 records of patients with Ph-negative MPN were reviewed, out of which 30.5% (n=59) patients had thrombosis. From the patients with MPN and thrombosis, the median age at diagnosis of MPN was 49 years (IQR 38-64) and 61% were women. Regarding the type of MPN, 74.6% (n=44) had polycythemia vera (PV), 16.9% (n=10) primary myelofibrosis (MF), and 8.5% (n=5) essential thrombocytosis (ET). JAK2 mutation was present in 86.4% and CALR in 5.1%. The diagnosis of thrombosis was made before or simultaneously with the diagnosis of MPN in 80% of cases, 89% in patients with SVT and 65.2% in patients with non-SVT (P=0.045). Venous thrombotic events occurred in 76.3% (n=45) and arterial events in 27.1% (n=16); 18.6% experienced more than one thrombosis
SVT represented 61% (n=36) of the total thromboses. Non-SVT included: 20.3% central nervous system, 10.2% deep vein thrombosis, 1.7% pulmonary embolism, and 6.8% other sites (jugular, retinal vein, aortic).
The median age at diagnosis of thrombosis was 51 years (range 18-85), and it was lower in the SVT group compared to the non-SVT group (45.5 years [range 18-74] vs 66 years [range 32-85], p=0.001), with 83% of the patients being younger than 60 years old. The prevalence of SVT by age group was as follows: 100% under 30 years (n=7), 81.8% (n=9) from 31-40 years, 72.7% (n=8) from 41-50 years, 61.5% (n=8) from 51-60 years, and only 23.5% (n=4) over 60 years. Female sex and age under 60 years were associated with SVT (OR 2.03, 95% CI 1.07-3.84, p=0.03 and OR 2.19, 95% CI 1.13-4.32, p=0.008, respectively). There were no differences in blood counts between patients with SVT and those with non-SVT.
SVT included 4 (11.1%) mesenteric vein thrombosis (MVT), 14 (38.9%) portal vein thrombosis, and Budd-Chiari syndrome presented in 18 patients (50%). Regarding complications, the most frequent was portal hypertension (PH) in 62.9%, followed by a combination of cirrhosis and PH in 22.9%; in patients with MVT, 75% required intestinal resection. Complications related to PH were frequent: 40% developed ascites, 30% portal biliopathy, esophageal varices presented in 83.3% and bleeding occurred in 53.3%. Endovascular procedures like transjugular intrahepatic portosystemic shunt (TIPS) to treat PH were performed in 26.7% of patients with portal hypertension (n=8/22).
The most frequently used anticoagulants were vitamin K antagonists (64.7%), followed by direct oral anticoagulants (32.4%), and low-molecular-weight heparin (2.9%). All patients received cytoreductive treatment.
Conclusions
SVT is prevalent in patients with MPN, occurring at a lower median age compared to those with non-SVT and showing a female predominance. Its occurrence is associated with significant complications, making it a leading cause of morbidity. In this cohort, the diagnosis of SVT occurred simultaneously with or prior to the diagnosis of MPN in most cases. This rate was higher than that reported in other cohorts from developed countries, highlighting the importance of considering a MPN diagnosis.