Patient-Specific Modelling of Blood Coagulation

Blood coagulation represents one of the most studied processes in biomedical modelling. However, clinical applications of this modelling remain limited because of the complexity of this process and because of large inter-patient variation of the concentrations of blood factors, kinetic constants and physiological conditions. Determination of some of these patients-specific parameters is experimentally possible, but it would be related to excessive time and material costs impossible in clinical practice. We propose in this work a methodological approach to patient-specific modelling of blood coagulation. It begins with conventional thrombin generation tests allowing the determination of parameters of a reduced kinetic model. Next, this model is used to study spatial distributions of blood factors and blood coagulation in flow, and to evaluate the results of medical treatment of blood coagulation disorders.

Clustering of Thrombin Generation Test Data Using a Reduced Mathematical Model of Blood Coagulation

Correct interpretation of the data from integral laboratory tests, including Thrombin Generation Test (TGT), requires biochemistry-based mathematical models of blood coagulation. The purpose of this study is to describe the experimental TGT data from healthy donors and hemophilia A (HA) and B (HB) patients. We derive a simplified ODE model and apply it to analyze the TGT data from healthy donors and HA/HB patients with in vitro added tissue factor pathway inhibitor (TFPI) antibody. This model allows the characterization of hemophilia patients in the space of three most important model parameters. The proposed approach may provide a new quantitative tool for the analysis of experimental TGT. Also, it gives a reduced model of coagulation verified against clinical data to be used in future theoretical large-scale modeling of thrombosis in flow.

Chrono-Pharmacological Study of Once Daily Curative Dose of a Low Molecular Weight Heparin (200IU antiXa/kg of Dalteparin) in Ten Healthy Volunteers

Low molecular weight heparin (LMWH) is currently prescribed for the treatment of deep vein thrombosis at the dose of 100 IU antiXa/kg twice daily or at a dose of 175 IU antiXa/kg once daily with a similar efficacy. We decided to study the chrono-pharmacology of curative dose of LMWH once daily administrated according to the one previously described with unfractionated heparin (UFH).

Ten healthy volunteers participated in an open three-period crossover study according to three 24 h cycles, separated by a wash-out interval lasting 7 days: one control cycle without injection, two cycles with subcutaneous injection of 200 IU antiXa/kg of Dalteparin (Fragmin®) at 8 a.m. or at 8 p.m. Parameters of heparin activity were analysed as maximal values and area under the curve.

Activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin time (PT) and tissue factor pathway inhibitor (TFPI) were higher after 8 p.m. injection than after 8 a.m. injection (p <0.05) while no chrono-pharmacological variation of anti factor Xa (AXa) activity was observed. Thus the biological anticoagulant effect of 200 IU antiXa/kg of Dalteparin seems to be higher after an evening injection than after a morning injection.

A chrono-therapeutic approach with LMWH, as prescribed once daily, deserves further investigation since our results suggest that a preferential injection time may optimise the clinical efficacy of these LMWH.

Thrombin generation and heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a severe complication of heparin therapy. IgG antibodies targeting the platelet factor 4-heparin complex activate platelets and generate microparticles with procoagulant activity.

OBJECTIVES

To determine whether the thrombin generation assay is capable of detecting procoagulant activity induced by patient platelet-poor plasma (PPP) in donor platelet-rich plasma (PRP).

PATIENTS AND METHODS

We explored two groups of patients; group 1 (n = 23): patients with a positive clinical and biological diagnosis of HIT; group 2 (n = 25): patients with a negative clinical and biological diagnosis of HIT. Mixtures of donor PRP and patient PPP (1:1) were incubated either with unfractionated heparin 0.2 U mL(-1) or with physiological saline. Thrombin generation was assessed by calibrated thrombinography. The effect of heparin on the mixtures was evaluated according to the ratio of the values with and without heparin (wH/woH) of the five thrombogram parameters.

RESULTS

With low heparin concentrations, plasma of group 1 activates donor platelets and generates procoagulant activity. A set of three ratios outside the cut-off values corresponds to the 'HIT thrombogram profile', characterized by a highly specific aspect of the thrombogram wH in relation to the thrombogram woH. None of the group 2 patients presented a HIT thrombogram profile. The results of thrombinography correlate well with the results of the platelet aggregation test.

CONCLUSION

Our studies illustrate the central paradox of HIT, namely enhancement of thrombin generation in the presence of heparin. The HIT thrombogram profile as it is defined in this study can detect the procoagulant activity of HIT IgG antibodies.

Danaparoid cross-reactivity with heparin-induced thrombocytopenia antibodies: report of 12 cases

PURPOSE

Danaparoid is a safe and effective drug for the treatment of heparin-induced thrombocytopenia (HIT). We describe an uncommon complication: danaparoid cross-reactivity with HIT antibodies.

DESIGN AND SETTING

A retrospective observational multicenter study on HIT was conducted in France. In this study concerning HIT patients treated with lepirudin, 12 patients were treated with lepirudin because danaparoid cross-reacted with the heparin-dependent antibodies.

RESULTS

Three groups of situations can be separated. In a first group, four patients received a short course of danaparoid until their initial functional HIT assay showed a cross-reactivity between danaparoid and HIT antibodies. One patient presented a fatal thrombotic complication but the relationship between this thrombotic complication and danaparoid cross-reactivity cannot be certain. In a second group, four patients received for 4 days at least a danaparoid treatment while the initial functional test did not show any danaparoid cross-reactivity. During danaparoid treatment, no significant increase of platelet count was observed and two patients presented a fatal thrombotic complication. In a third group, cross-reactivity between danaparoid and HIT antibodies was not checked before danaparoid therapy. During danaparoid treatment, no significant increase of platelet count was observed and the four patients developed a venous thromboembolic complication.

CONCLUSION

Absence of any increase in platelet count after 3 to 5 days of danaparoid therapy and/or the occurrence of a new thrombotic event should lead to danaparoid cross-reactivity suspicion. However, before attributing thrombotic complications to danaparoid cross-reactivity, it is crucial to verify that the patients received the recommended danaparoid dosage regimen.

Poor anticoagulant response to tissue factor pathway inhibitor in patients with venous thrombosis

Tissue factor pathway inhibitor (TFPI) is of major importance in regulating the coagulation triggering effects of tissue factor. An association between TFPI deficiency and thrombosis has still not been clearly demonstrated. We evaluated the anticoagulant activity of exogenous TFPI added either to the plasma of patients with venous thrombosis (n = 118) or to the plasma of healthy controls similar in terms of mean age and sex ratio (n = 107). A poor anticoagulant response to TFPI, defined as TFPI resistance, was observed in 4.7% of controls and in 11.0% of patients. TFPI resistance was associated with an almost threefold increase in the risk of thrombosis and could therefore represent a novel hemostatic risk factor for venous thrombosis.

Heparin-Induced thrombocytopenia: minimising the risks in the elderly patient

Heparin therapy may sometimes be seriously complicated by heparin-induced thrombocytopenia (HIT). Heparin use for treatment and prevention of thromboembolism is more common in the elderly and that may be the reason why HIT is reported more frequently in this group of patients. The first approach in the management of HIT is awareness of this disorder. The morbidity and mortality associated with HIT may be reduced by avoiding unnecessary heparin exposure, by reducing the duration of heparinisation and by using low molecular weight heparins rather than unfractionated heparin. A decrease from baseline values of at least 30% in the platelet count, any unexplained thrombotic event and the finding of a white clot at thrombectomy are clinical warning signs that should alert physicians to a possible diagnosis of HIT. Indeed, early clinical recognition of HIT may sometimes prevent the severe complications associated with this disorder. Objective confirmation of the diagnosis of HIT is difficult because none of the available biological tests possess 100% sensitivity or 100% specificity. It is, however, possible to optimise the performances of the functional assay, mainly the platelet aggregation test (PAT), by following the manoeuvres described by differ- ent investigators. The use of 2 classes of assay (functional and antigen assays) and repeat testing on another day can avoid misdiagnosis of HIT. An alternative parenteral anticoagulant treatment is most often mandatory after heparin withdrawal. Danaparoid sodium and lepirudin are 2 drugs that are currently available for the treatment of HIT, and the efficacy of argatroban needs to be confirmed in greater numbers of patients with HIT. The use of these drugs has contributed to the reduction in the mortality and morbidity associated with HIT.

[Hemorrhagic syndromes related to selective serotonin reuptake inhibitor (SSRI) antidepressants. Seven case reports and review of the literature]

PURPOSE

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed. Since their release unexpected adverse effects such as bleeding disorders have been described.

METHODS

Thirty patients with either hematoma or muco-cutaneous bleeding have been selected from case reports of the Saint-Etienne Pharmacovigilance center and from a literature review.

RESULTS

The female/male sex-ratio was 3:4 and the mean age 42 years. Two newborns who had been exposed in utero to SSRIs were also included in the study. Eleven patients presented an underlying disease or were at risk. Various adverse effects such as bruising, hematoma, petechiae or purpura, epistaxis, and more rarely intestinal hemorrhage, ocular bleeding or cerebral hemorrhage were encountered. Symptoms were sometimes associated with prolonged bleeding time and platelet aggregation disorders and usually resolved within two days to four months after treatment discontinuation.

CONCLUSION

Hematoma and muco-cutaneous bleeding would therefore be related to treatment, including selective serotonin reuptake inhibitors. However, these adverse effects are still poorly known and rarely reported. The main mechanism suggested would be a decrease in serotonin platelet leading to a defect in platelet aggregation. However, an increase in capillary fragility or susceptibility related to the patient's condition might be involved. Study of hemostasis history in patients requiring treatment with SSRIs might be of value.

Efficacy and safety of danaparoid sodium (ORG 10172) in critically ill patients with heparin-associated thrombocytopenia

OBJECTIVE

To evaluate the effectiveness and the safety of danaparoid sodium in the treatment of critically ill patients with standard unfractionated heparin-induced thrombocytopenia (HIT) or low-molecular-weight HIT.

SETTING

University hospital.

PATIENTS AND METHODS

Retrospective analysis of 42 consecutive critically ill patients who were admitted for HIT between October 1992 and February 1997 and were treated either with therapeutic or prophylactic doses of danaparoid sodium.

RESULTS

Among the 26 patients treated with therapeutic doses, neither new thrombotic complications nor thrombosis extension was clinically suspected. Two deaths were directly related to lower limb acute arterial thrombosis associated with HIT. Two major hemorrhagic complications were observed when aspirin in addition to danaparoid sodium was administered. When danaparoid sodium was used in prophylactic doses (20 courses of treatment) to prevent either postsurgical or medical thrombotic complications, no thrombotic event was observed. No death related to HIT or danaparoid sodium treatment was observed. One aggravation of a postsurgical cerebral lesion was observed. During danaparoid sodium treatment, a persistence or a recurrence of thrombocytopenia was observed in 6.5% of patients without thrombotic complications.

CONCLUSION

Danaparoid sodium appears to be an efficient and safe treatment in critically ill patients with HIT. The concomitant use of aspirin in addition to danaparoid sodium seems to represent an important additional hemorrhagic risk that should be avoided in patient management.

Pharmacokinetic and pharmacodynamic variations of acenocoumarol orally administrated either once or twice daily in patients with deep venous thrombosis

The literature suggests that variations in anticoagulant effect occur when acenocoumarol is administrated in a daily dose. We assessed the anticoagulant effects of acenocoumarol with INR, factors VII and X and protein C in 12 randomly selected hospitalised patients with deep-vein thrombosis, six of them receiving a daily dose of acenocoumarol, the other six receiving twice daily doses. When the drug effect had been at a steady-state for at least 72 h, five blood samples were drawn per patient over a period of 24 h. No nycthemeral significant variations were noted for INR, factor X and protein C in the two groups (P > 0.10). Nycthemeral significant variation in factor VII when acenocoumarol was administered once daily was noted (P = 0.02), but the clinical relevance of factor VII variation at steady-state is uncertain. In spite of the short pharmacokinetic half-life of acenocoumarol, a stable nycthemeral pharmacodynamic activity was observed after once daily administration; twice-daily administration of acenocoumarol does not appear to be justified.

Prevalence of factor V Leiden (APCR) and other inherited thrombophilias in young patients with myocardial infarction and normal coronary arteries

OBJECTIVE

To investigate the role of activated protein C resistance (APCR, factor V Leiden) in coronary artery thrombosis.

METHODS

The prevalence of APCR and of congenital deficiencies of antithrombin III, protein C, protein S, plasminogen, and factor XII was investigated in adult patients under 45 years of age with acute myocardial infarction. The results were compared with those of a group of 53 age and sex matched control subjects.

RESULTS

Among 75 patients under the age of 45 years who were admitted from November 1994 to April 1996 for acute myocardial infarction, 22 (29.3%) had normal coronary arteriography (group I) and 53 (70.7%) had significant coronary artery disease (group II). Inherited thrombophilia was more often found in group I (4/22, 18.2%) than in group II (4/53, 7.5%) but the difference was not significant (F test: p = 0.22). The prevalence of APCR was 9.1% (2/22) in group I, 3.8% (2/53) in group 2 (p = 0.57), and 3.8% (2/53) in the normal control group (p = 0.57).

CONCLUSIONS

The prevalence of congenital thrombophilias, including APCR, does not seem to be increased in young patients with myocardial infarction and normal coronary angiograms, compared with young patients with coronary atherosclerosis and with normal control subjects. However, the statistical power of the study is too low to detect a significant difference and these results are published to allow a meta-analysis of this problem in the future.

Evaluation of D-dimer ELISA test in elderly patients with suspected pulmonary embolism

STUDY OBJECTIVE

To determine the clinical usefulness of D-dimer ELISA test in elderly patients with clinically suspected pulmonary embolism (PE).

DESIGN

Prospective cohort study.

PATIENTS

Ninety-six consecutive outpatients older than 70 years with a duration of symptoms shorter than one week and without metastatic cancer or recent surgery, trauma, infection, stroke, myocardial infarction, deep vein thrombosis (DVT) or PE, or treatment with curative doses of heparin or oral anticoagulant.

INTERVENTION

All patients underwent at least ventilation/perfusion scan and bilateral ultrasonic duplex scan and a blood sample collection within 24 hours of admission. When necessary a pulmonary angiography and/or a bilateral venography were also performed. Patients were classified as follows: (1) PE-positive: positive angiography or high probability V/Q scan and deep vein thrombosis (proven either by venography or by ultrasonic duplex scan) or non high probability V/Q scan and either DVT (proven at presentation by venography or by ultrasonic duplex scan) or symptomatic thromboembolic event within 3 months of follow-up; or (2) PE-negative; normal V/Q scan or normal angiography or non high probability V/Q scan and either negative ultrasonic duplex scan or normal venography and low clinical probability and absence of symptomatic thromboembolism within 3 months of follow-up. D-dimer measurements were performed using both a conventional and a single semi-quantitative ELISA test (Asserachrom D-di, Instant I.A.D-dimer).

RESULTS

Using a cutoff value of 500 ng/ml, the conventional ELISA D-dimer test showed a sensitivity and a negative predictive value of 100% with poor specificity and positive predictive value of 14.3% and 45.5% respectively. The new rapid semi-quantitative D-dimer test displays worse results with sensitivity, negative predictive value, specificity and positive predictive value of 92.3%, 82.4%, 25% and 46% respectively.

CONCLUSION

In a geriatric population, conventional ELISA D-dimer is a good marker to exclude PE but, due to the comorbid conditions, only a few patients presented with D-dimer values less than 500 ng/ml.

Evolution of blood coagulation and fibrinolysis parameters after abrupt versus gradual withdrawal of acenocoumarol in patients with venous thromboembolism: a double-blind randomized study

A double-blind randomized trial was conducted to research a hypercoagulable state rebound after abrupt versus gradual withdrawal of acenocoumarol, 20 patients were included: 10 in the abrupt withdrawal group (AW) and 10 in the gradual withdrawal group (GW). Between days 1 and 15,F1 + 2 was higher in group AW (P < 0.002). A significant increase of D-dimer with time was found (P < 0.001) without difference between the two groups, tPA and PAI-1 levels remained stable throughout without difference between the two groups. No rebound phenomenon was observed. Four thrombotic recurrences were observed: group AW: 1, group GW: 3 (P = 0.29). There is neither clinical nor biological support for a gradual anticoagulation withdrawal.

Effects of long travels in sitting position in elderly volunteers on biological markers of coagulation activation and fibrinolysis

OBJECTIVE

To evaluate whether long travel in sitting position is associated with an increase of coagulation activation and/or a decrease of fibrinolytic activity.

DESIGN

Comparison of blood coagulation and fibrinolysis parameters before and after two pleasure trips by bus organized in winter period (600 km in 8 hours) and in summer period (1200 km in 16 hours).

SUBJECTS

31 and 23 healthy elder volunteers for the winter and the summer trip respectively. Nine other elder volunteers were selected as a control group for the winter study.

MAIN OUTCOME MEASURES

prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin III (TAT), D-dimers (D-D), factor VII activated, plasminogen activator inhibitor (PAI), tissue-type plasminogen activator (t-PA), plasma albumin.

RESULTS

A significant difference before and after the travel was only observed for TAT in the summer period. However all values of TAT were in the normal range. No volunteer presented with thromboembolic disease during the month following the travel.

CONCLUSION

In the condition of our study, long travel in sitting position does not lead to an enhanced procoagulant state for elderly with varicose veins. These results suggest that there is no biological support to propose heparin prophylactic therapy for the elderly with varicose veins wishing to travel by bus.

[Thrombopenia induced by heparin: treatment with Org 10172. Tolerability and efficacy]

OBJECTIVES

Heparin-induced thrombocytopenia is a relatively common and potentially serious adverse complication of heparin treatment. After heparin withdrawal initiation of an alternative anticoagulant is often indicated. Org 10172 or Orgaran is a mixture of several non-heparin low molecular weight glycosaminoglycans with proven antithrombotic efficacy. Unlike low molecular weight heparins, Org 10172 has a low cross reaction rate (about 10%) with the heparin-dependent antibody.

METHODS

We present nine patients with heparin induced thrombocytopenia. Org 10172 was prescribed to treat or to prevent a thromboembolic event.

RESULTS

Seven patients required further parenteral anticoagulant at diagnosis of heparin-induced thrombocytopenia. Org 10172 was given at prophylactic doses for three patients with a high thrombosis risk and at therapeutic doses for four patients who presented either a venous or an arterial thrombosis related to thrombocytopenia. Two patients presented heparin-induced thrombocytopenia four to six years earlier and needed a parenteral anticoagulation treatment in a post-operative period.

CONCLUSION

For the nine patients, Org 10172 was a safe and effective antithrombotic treatment. However, strict monotoring of the platelet count is absolutely mandatory during Org 10172 therapy.

[Thrombotic thrombocytopenic purpura disclosing cancer: apropos of 2 cases]

Thrombotic thrombocytopenic purpura (TTP) causes severe haemolytic anaemia, thrombopenia, fever and neurological and renal involvement. Currently five large aetiologic groups have been identified: viral or bacterial infection, drugs, conjunctive tissue diseases, pregnancy and solid tumours. We observed two cases resulting from an adenocarcinoma. In the first case, a 71-year-old man with chronic silicosis, the presenting signs were asthenia, fever, epistaxis with diffus purpura and spontaneous haematomas of the lower limbs. Diagnosis of TTP was based on routine laboratory tests and the patient responded well to fresh frozen plasma. On the 5th day of treatment, haemoglobin level dropped sharply and melana occurred. Upper digestive tract endoscopy revealed a tumoural formation of the antrum-fundic junction and histology examination of the biopsy confirmed the diagnosis of adenocarcinoma. Ten months after gastrectomy the patient was in excellent health with no relapse of the TTP. In the second case, the presenting signs included spontaneous haematomas, rectorrhagia and low grade fever. Microscopic haematuria and renal failure were observed in addition to the biological syndrome of TTP. The patient responded poorly to fresh frozen plasma and packed cell transfusions. Plasma exchange was equally unsuccessful. The disease continued a fulminant course and the diagnosis of adenocarcinoma located in a pulmonary lymph nodes was made at autopsy. These rare cases of TTP caused by cancer emphasize the importance of a thorough aetiological research. Plasma exchange has been shown to be effective but mortality at 1 year approximately 85% in cancer related cases. Early diagnosis and specific anti-cancer therapy might improve prognosis. We report our personal experience with 16 other similar cases.

Fibrinolysis and elastic compression: no fibrinolytic effect of elastic compression in healthy volunteers

The local and systemic fibrinolytic response to the placing of elastic compression in healthy volunteers was studied to determine whether this method of preventing venous thromboembolism has any profibrinolytic effect, as previously demonstrated with intermittent pneumatic compression. Variations in the major parameters of fibrinolysis (euglobulin lysis time, t-PA antigen, PAI-1 antigen, PAI-1 activity) were studied in an open randomized cross-over study in 21 healthy volunteers, in which three types of treatment were tested for periods of 24 h each (without elastic compression, elastic compression of an upper limb, elastic compression of the lower limbs). Four blood samples were taken from the upper limb during each period (at 08:00 h, 10:00 h, 18:00 h, 08:00 h on the following day). The placing of elastic compression did not cause any statistically significant change in the four parameters tested between the three types of treatment. In contrast, circadian rhythm was confirmed for all the fibrinolytic factors studied with a minimal fibrinolytic activity in the morning and a maximal activity in the evening. Elastic compression does not seem to have any profibrinolytic effect in healthy volunteers but other studies are needed in patients before a definitive conclusion can be reached.

Pentosan polysulfate-induced thrombocytopenia and thrombosis

Pentosan polysulfate is a low-molecular-weight sulfated polysaccharide used as an antithrombotic drug. We present two patients who developed thrombocytopenia and venous thrombosis during treatment with pentosan polysulfate. The relationship between pentosan polysulfate and thrombocytopenia is supported by platelet aggregation and serotonin release tests. In the light of the literature and our two cases, it appears that pentosan polysulfate alone as standard heparin and low-molecular-weight heparin can induce thrombocytopenia and thrombosis. Platelet counts should therefore be periodically monitored during pentosan polysulfate treatment. In the case of pentosan polysulfate-induced thrombocytopenia, it seems that heparin or low-molecular-weight heparin should not be instituted during the acute phase even if platelet aggregation studies are negative, because of their low sensitivity. After remission of thrombocytopenia, whether or not glycosaminoglycans can be reinstituted, at least temporarily, after antibody had disappeared is still an open question.

[Chronopharmacology of fractionated heparin (nadroparin) administrated by subcutaneous route at prophylactic doses in healthy volunteers]

This study evaluated the effect of injection time on pharmacodynamic of a single subcutaneous bolus of nadroparine (7500 anti-Xa IC U) evaluated by anti-Xa activity (Hepaclot and Heptest) and by activated partial thromboplastin time (APTT by auto PTT reagent). 10 healthy male volunteers were studied at 4 different 24 hours periods with 4 different injection times (6 am, 12 am, 6 pm, 12 pm) and with a one week wash-out period between each period. No chronopharmacological variation of the anti-Xa activity evaluated by Hepaclot was found. However the anti-Xa activity evaluated by Heptest was higher at the sixth hour after 12 am injection (p = 0.0022). No difference on APTT values was observed whatever the injection time. So the injection time of nadroparine has a weak influence on anti-Xa activity and no effect on APTT; Before to conclude on the lack of chronopharmacological effect of nadroparine, it seems necessary to evaluate such a possibility with higher dosage, with sick and older subjects.

Intravenous prostacyclin in thrombotic thrombocytopenic purpura: case report and review of the literature

The use of prostacyclin infusion in thrombotic thrombocytopenic purpura is consistent with the hypothesis that patients may lack a plasma factor stimulating prostacyclin production. However, prostacyclin therapy, alone or in combination with aspirin, dipyridamole, steroid and plasmapheresis, failed in many cases. We here describe the case of a patient who responded dramatically to a combination of prostacyclin and plasma infusions, after conventional therapy had failed (plasmapheresis, fresh frozen plasma infusions). Prostacyclin was infused intravenously initially for 120 h from 4 to 9 ng kg min-1 and then continuously for 48 h at 9 ng kg min-1. Despite the scarcity of case reports in the literature, we conclude that the failure of prostacyclin in thrombotic thrombocytopenic purpura appears to be related to insufficient doses and/or duration of therapy.