Katcharin Aryurachai

Pulmonary arterial hypertension in previously splenectomized patients with β-thalassemic disorders

Our aim was to study the cause and describe the clinical features of pulmonary arterial hypertension (PHT) in splenectomized β-thalassemia (β-Thal) patients. Ten splenectomized β-Thal patients with systolic pulmonary artery (PA) pressure >30 mm Hg were evaluated by echocardiography, right-heart catheterization, and pulmonary angiography. Five of these patients later underwent hemodynamic studies. Echocardiography and pulmonary angiography on the 10 patients showed normal values of left ventricular systolic function and no findings of acute or chronic pulmonary embolism. Hemodynamic evaluation showed very high PA pressures associated with markedly increased pulmonary vascular resistance indices (PVRIs). Hematological evaluation of the 10 patients showed marked anemia, markedly increased numbers of nucleated red blood cells (nRBCs), and serum ferritin. Mean platelet count, plasma β2 thromboglobulin, and thrombin—antithrombin III complex levels were significantly increased. It was concluded that PHT can be found in splenectomized β-Thal patients. Features associated with PHT were female sex, hemoglobin E/β-Thal, status many years postsplenectomy, marked anemia, markedly increased nRBC count, thrombocytosis, and very high serum ferritin levels. PHT was not due to pulmonary emboli. Our findings suggested that severe PHT was due to increased PVRI from thrombotic pulmonary arteriopathy, likely from chronic low-grade hypercoagulability and platelet activation after splenectomy.

Relationship between hypercoagulable state and erythrocyte phosphatidylserine exposure in splenectomized haemoglobin E/β-thalassaemic patients*

Summary. Small pulmonary arterial thromboses can occur following splenectomy of patients with haemoglobin E/β‐thalassaemia (Hb E/β‐thal). We compared plasma markers of coagulation activation in vivo and red blood cell (RBC) markers of procoagulant activity in 15 Hb E/β‐thal patients who were not splenectomized (NS), 15 who had been splenectomized (S), and 15 normal controls (NC). Levels of plasma thrombin–antithrombin III complex (TAT) were significantly higher in the S group than in either the NS or the NC groups, and levels of prothrombin fragment 1.2 (F 1.2) were significantly higher in the S than in the NC group. Diluted Russells viper venom clotting times were significantly shorter when RBCs from group S patients were added to the assay compared with RBCs from the NC group. Phosphatidylserine (PS) expression (% of annexin V‐positive RBCs) on the outer leaflet of RBC membrane of both ‘larger’‐ and ‘smaller’‐sized RBCs was significantly higher for the S than the NC group. The RBC PS expression of the S and the NS groups, respectively, accounted for 25·3% (P = 0·174) and 6·3% (P = 0·675) of the variation in plasma TAT levels. Our findings indicated that, when compared with NC, splenectomized patients with Hb E/β‐thal were in a chronic low‐grade hypercoagulable state associated with increased numbers of circulating PS exposed RBCs. This condition may have a role in the risk of these patients for pulmonary arterial thromboses.

In vivo Platelet Activation and Hyperaggregation in Hemoglobin E/β-Thalassemia: A Consequence of Splenectomy

Patients with hemoglobin E/β-thalassemia (E/β-Thal) who have undergone splenectomy are prone to thrombosis in the small pulmonary arteries.To study the role of platelets in this situation, we assayed plasma β2-thromboglobulin (βTG) and performed whole blood platelet aggregation analysis of 30 E/β-Thal patients, half of whom had undergone splenectomy.We compared results with those obtained with 15 healthy control subjects. Plasma βTG levels in splenectomy patients were significantly higher than in control subjects and patients who had not undergone splenectomy, and platelets in splenectomy patients exhibited hyperaggregation in response to adenosine diphosphate, thrombin, and ristocetin. Levels of plasma thrombin-antithrombin III complex were also significantly higher. This finding is likely due to an increased number of erythrocytes with exposed phosphatidylserines, an effect that has been associated with splenectomy. The increased presence of thrombin in the blood may well be the cause of platelet hyperactivity, which was evident only in the asplenic patients. Platelet hyperactivity very likely plays a pathogenetic role in the thrombosis of small pulmonary arteries that occurs in E/β-Thal patients who have undergone splenectomy.

Risk factors of venous thromboembolism in thai patients.

Venous thromboembolism (VTE) has been reported to be less common among Thais than Caucasians. Whether this observation reflects genetic or environmental factors, or both, is uncertain. To identify genetic and acquired risk factors of Thai patients with VTE, we enrolled in the study 105 consecutive Thai patients (34 men, 71 women) who had an objectively confirmed history of VTE. A complete clinical summary was obtained from each patient, with emphasis on personal and family history of VTE, as well as circumstantial vascular risk factors (surgery, immobilization, pregnancy, postpartum condition, trauma, oral contraceptive use, and malignancy). Of the 105 patients, 19% were found to have a malignancy. The mean age at the time of the first thrombotic episode was 52.1 years (range, 29–76 years), compared with 42.6 years (range, 17–82 years) for the patients without malignancy. Of the 85 patients without malignancy, 12.3% had protein S deficiency, 8.9% had protein C deficiency, 4.7% had antithrombin deficiency, 10.4% had antiphospholipid antibody, 30.4% had an elevated factor VIII level, 26.8% had an elevated factor XI level, 5.3% had hyperhomocysteinemia, and 16.5% were on oral contraceptives before the thrombotic episode. Factor V Leiden, the G20210A prothrombin gene mutation, and homozygosity for the C677T methylenetetrahydrofolate reductase (MTHFR) gene variant were not found. The VTE in 7.1% of the patients was considered to be secondary to recent surgery, trauma, and/or immobilization. Compared with studies of Caucasian patients, there were significant differences in the risk factors for VTE, with protein S deficiency and protein C deficiency being more common in the Thai patients. In contrast, factor V Leiden, the G20210A prothrombin gene mutation, and the C677T MTHFR gene mutation are not genetic risk factors among Thai patients with VTE. Malignancy and the use of oral contraceptives were the most common acquired risk factors for VTE in the Thai patients.

Intravascular Hemolysis, Vascular Endothelial Cell Activation and Thrombophilia in Splenectomized Patients with Hemoglobin E/β-Thalassemia Disease

The relationship between asplenia and thrombophilia in β-thalassemia disease patients is not yet completely understood. One hundred and ten adult hemoglobin (Hb) E/β-thalassemia (E/β-Thal) disease outpatients, dichotomized according to the presence or absence of the spleen, were prospectively studied for evidence of intravascular hemolysis (IVH) and vascular endothelial cell (EC) activation. Biomarkers of IVH (serum cell-free Hb), EC [soluble E-selectin (sE-selectin) and soluble vascular cell adhesion molecule 1 (sVCAM-1)], platelet and EC [soluble P-selectin (sP-selectin)], inflammation [high-sensitivity C-reactive protein (hs-CRP)], and coagulation [thrombin-antithrombin complexes (TAT)] activation, as well as other selected blood tests were determined. The 61 splenectomized patients had a more severe hemolytic disease and higher levels of cell-free Hb and ferritin (p = 0.003), sE-selectin, sP-selectin, hs-CRP, and TAT (p < 0.05). However, serum levels of sVCAM-1 were not different between the two groups. The findings suggested IVH and EC activation. Together with chronic iron overload and chronic low-grade inflammation activation, the findings extend our understanding of the mechanism of thrombophilia in splenectomized E/β-Thal disease patients.

Correction of coagulation and inflammation activation by chronic blood transfusion in an asplenic patient with haemoglobin E/β-thalassaemia and pulmonary arterial hypertension

Dear Sir, Chronic low-grade coagulation and systemic inflammation have been shown to be associated with increased amount of circulating phosphatidylserine-exposing red blood cells (PS-RBCs) in splenectomised haemoglobin E/β-thalassaemia (E/β-Thal) patients (Atichartakarn et al., 2002; Banyatsuppasin et al., 2011), some of whom may also have pulmonary arterial hypertension (PAH) due to thrombotic pulmonary arteriopathy (TPA) (Atichartakarn et al., 2003). Blood transfusion is recommended in the management of this complication (Cogliandro et al., 2008). However, the role of transfusion in modulating the pathophysiology of this condition is poorly described. We gave chronic blood transfusion to a splenectomised E/β-Thal patient with PAH and showed a concomitant reduction in the amount of circulating PS-RBCs, level of plasma thrombin antithrombin complex (TAT), pulmonary vascular resistance and PA pressure (Atichartakarn et al., 2004). The findings suggest that there is a role of PS-RBCs and hypercoagulability in the pathogenesis of TPA-associated PAH. Because of the close relationship between inflammation and coagulation (Esmon, 2003), studying concomitant changes in biomarkers of inflammation could extend our understanding of the hypercoagulable state in these patients. Therefore, sera of this patient were assayed for soluble tumour necrosis factor-α receptors I & II (sTNFR I & II) as sensitive surrogate biomarkers of inflammation (Hanai et al., 2004). Here, we report the findings. All treatment programs and interventions were clearly explained to the patient and signed written consent was obtained. Approval from the Ramathibodi Hospital Institutional Ethics Committee (# 105/1997) was also obtained. Complete blood count; haemoglobin (Hb) typing; serum ferritin; plasma TAT; serology for hepatitis B (HBV), hepatitis C (HCV) and human immunodeficiency virus (HIV) and the amount of PS-RBCs were determined as detailed previously (Atichartakarn et al., 2004). Levels of serum sTNFR I & II were determined by enzyme-linked immunoassay kits (R&D system, Minneapolis, MN) on samples stored at −70 ◦C.

Low prevalence of heparin-induced thrombocytopenia after cardiac surgery in Thai patients

INTRODUCTION Heparin induced-thrombocytopenia (HIT) has been well recognized in Western countries. However, there are no data in the Thai population. We therefore investigated the prevalence of anti-platelet factor 4 (PF4)/heparin antibodies, HIT, and its thrombotic complications in Thai patients undergoing cardiac surgery using unfractionated heparin. MATERIALS AND METHODS Seventy-three consecutive patients were prospectively enrolled in this study. Blood samples before operation and week 1, week 2, and week 3 after operation were collected from each patient for HIT antibody screening by enzyme-linked immunosorbent assay using IgG antibody specific to the PF4/heparin complex. Positive samples were further analyzed by (14)C-serotonin release assay. Complete blood count was performed daily during the first week, then weekly for 3 weeks. RESULTS No patient had detectable anti-PF4/heparin antibodies at baseline. Five patients sero-converted during the course of the study for anti-PF4/heparin IgG: 3 (4.1%) at week 1, 4 (5.5%) at week 2, and 5 (6.8%) at week 3 after surgery. However, none of these patients had anti-PF4/heparin antibodies that resulted in (14)C-serotonin release to be considered clinically significant antibodies. Post-operative thrombocytopenia after the operation was found in 35 patients (47.9%), but was not considered to be caused by HIT. Thromboembolic events occurred in 3 patients (4.1%) during follow up; however, none of these patients had positive PF4/heparin antibody tests. CONCLUSIONS Our study represents the first study to examine Thai patients exposed to heparin in the context of cardiac surgery. We found a lower prevalence of positive anti-PF4/heparin antibodies and clinical HIT than previously published studies.