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A huge right ventricular thrombosis and pulmonary thromboembolism in a child with acute lymphoblastic leukemia

To the Editor: Thromboembolism (TE) is a significant complication of acute lymphoblastic leukemia (ALL), and it is associated with increased risk of morbidity and mortality.1-4 Recent reports showed that chemotherapeutic agents including L-asparaginase and corticosteroids, andpatient factors such as age, blood type, and the presence of inherited or acquired thrombophilia may affect the development of TE.1,2,4 Venous TE usually occurs as deep vein thrombosis in the extremities, pulmonary TE, and cerebral venous sinus TE.5 However, intracardiac thrombosis has been rarely reported.1,2 Wepresent a case of amassive right ventricle (RV) thrombosis and pulmonary TE in a child with T-cell ALL, and discuss the management strategy of TE in these critically ill patients. A 9-year-old female child was diagnosed with T-cell ALL. The white blood cell (WBC) countwas 206× 109/L (blast 90%) and platelet count was 70 × 109/L. A routine echocardiography done before starting remission induction chemotherapy showed a huge mobile homogeneous echogenic mass with irregular margins in the RV (Figure 1A). The mass extended from the tricuspid valve to the pulmonary valve through the RV outflow tract, resulting in RV inflow and outflow track obstruction (Figure 1B and C). Chest X-ray showed a haziness and pleural effusion in the right lower lung field. Computed tomography (CT) also showed a huge mass in the RV (Figure 1D) and pulmonary TE in the right lower pulmonary artery with a right lower lung infarction (Figure 1E). Despite prephase steroid treatment, hyperleukocytosis with peripheral blasts persisted, mandating urgent initiation of chemotherapy. Although the RV mass posed a risk of potentially fatal further pulmonary TE, the patient was started on remission induction chemotherapy with lowmolecular weight heparin (LMWH) to prevent further TE complications. LMWH was maintained during the 4 weeks of remission induction chemotherapy and 2 weeks of cell count recovery. After remission induction chemotherapy, bone marrow study confirmed complete remission with full recovery of peripheral blood cell counts. Follow-up echocardiography and CT showed no significant change in the size and configuration of the RV thrombus and TE in the right pulmonary artery. Then surgical RV thrombectomy and pulmonary thromboendarterectomywere performed. The patient was classified as a very high risk group due to the high initial WBC count, according to our institutional risk group classification scheme.6 In addition, considering poor response to prephase steroid treatment, it was anticipated that the risk of leukemia relapse would be significant. Therefore, she received cord blood stem cell transplantation in the first remission period while maintaining LMWH. Echocardiography done 1 month after transplantation showed a small organized thrombus in the tricuspid valve without new thrombi in the heart. LMWH was discontinued at discharge. Hematopoietic stem cell transplantation was successful and she is doing well without any cardiovascular symptoms. Venous TE is a common complication in patients with ALL. Most thrombotic events occur in the induction phase, when the disease is still active and cytolysis of blasts results in secretion of procoagulants or damage to fibrinolytic or anticoagulant pathways, possibly inducing thrombogenesis.5,7 One recent study reported that T-cell subtype of ALL is significantly associated with the development of venous TE.8 In children, older age (>7 or 10 years) is one of the main risk factors of symptomatic TE.1,4,8 Chemotherapeutic agents including Lasparaginase and corticosteroids further enhance thehypercoagulable state.2,3 In our 9-year-old patient, a huge thrombus was found in the RV, not in common sites of TE such as the upper or lower extremities or central venous sinus. In addition, the thrombus developed before chemotherapy or central venous catheter insertion, which are wellknown risk factors of thrombogenesis. Therefore, we speculated that thehuge thrombus formation in theunusual site at the very early phase of diagnosis was related to the cancer itself in a relatively older child (>7 years) with T-cell ALL and advanced tumor burden manifest as hyperleukocytosis.5,7,8 The treatment options for TE are thrombolytic therapy, anticoagulation, surgical removal, and percutaneous thrombectomy.9-12 However, it was difficult to decide on the right time and treatment options for patients who present with such severe TE at diagnosis. Thrombolytic therapy could not be considered because of preexisting bleeding tendency. Surgical option was also very risky because of bleeding tendency, decreased immunity, and concerns for delayed wound healing after operation. In addition, the patient had a risk of earlymortality by bleeding due to hyperleukocytosis if the chemotherapy were to be delayed. Therefore, we decided to proceed with remission induction chemotherapy with anticoagulation initially. After confirming complete remission and stabilization of patient’s clinical conditions, surgical RV thrombectomy and pulmonary thromboendarterectomy were performed. American College of Chest Physicians recommends that LMWH should be used for at least 3months to treat