Variability of residual platelet function despite clopidogrel treatment in patients with peripheral arterial occlusive disease

Residual platelet function despite treatment with clopidogrel may predict an unfavourable cardiovascular outcome. The majority of studies have investigated the effects of clopidogrel administration in conjunction with aspirin in patients undergoing percutaneous coronary intervention. The primary objective of the present study was to assess the platelet response to clopidogrel in the absence of aspirin in patients with peripheral arterial occlusive disease (PAOD) and to investigate whether non-responsiveness to clopidogrel is reproducible during long-term follow-up. Fifty-four clinically stable PAOD patients on a maintenance dose of 75 mg/d clopidogrel were enrolled in this study. Platelet function was assessed at baseline and after a median follow-up of 18 months using light transmittance aggregometry (LTA) with 2 microM ADP as an agonist. HPLC-coupled mass spectrometry was used to detect clopidogrel and clopidogrel carboxylic acid, the main metabolite of clopidogrel. Residual platelet function, as defined by late aggregation values within the reference range (i.e., >43%), was observed in 35.2% of patients at baseline and 17.6% during follow-up. During the observation period, 26.5% had switched from responder to non-responder status or vice versa. Among non-responders, either clopidogrel or its metabolite was detected in 89.5% and 83.3% of patients at baseline and at follow-up, respectively. We conclude that non-responsiveness to clopidogrel as determined by ADP-induced LTA is not stable over time. This phenomenon cannot be attributed to non-compliance alone.

[Medicinal therapy for interventional surgery of the peripheral vascular system]

The aim of medicinal treatment, during and after femoral and crural interventions is to prevent early or late onset arterial thrombosis of the treated vascular segments. Therefore, unfractionated heparin is administered during the intervention by an intra-arterial or intravenous approach. To avoid late onset thrombosis, administration of platelet function inhibitors is recommended. However, valid data are only available for acetylsalicylic acid (ASA). Therefore, ASA is recommended for long term medication. In several cardiological studies on stent implantation in coronary vessels the combination of ASA and clopidogrel for dual platelet inhibition has been proven to be effective. These results have been transferred to antithrombotic therapy of the lower extremities despite the lack of dedicated studies. There is no evidence for the use of vitamin K antagonists after peripheral interventions.

Incidence and causes of heparin-induced skin lesions

BACKGROUND

Little is known about the incidence and causes of heparin-induced skin lesions. The 2 most commonly reported causes of heparin-induced skin lesions are immune-mediated heparin-induced thrombocytopenia and delayed-type hypersensitivity reactions.

METHODS

We prospectively examined consecutive patients who received subcutaneous heparin (most often enoxaparin or nadroparin) for the presence of heparin-induced skin lesions. If such lesions were identified, we performed a skin biopsy, platelet count measurements, and antiplatelet-factor 4 antibody and allergy testing.

RESULTS

We enrolled 320 patients. In total, 24 patients (7.5%, 95% confidence interval [CI] 4.7%-10.6%) had heparin-induced skin lesions. Delayed-type hypersensitivity reactions were identified as the cause in all 24 patients. One patient with histopathologic evidence of delayed-type hypersensitivity tested positive for antiplatelet-factor 4 antibodies. We identified the following risk factors for heparin-induced skin lesions: a body mass index greater than 25 (odds ratio [OR] 4.6, 95% CI 1.7-15.3), duration of heparin therapy longer than 9 days (OR 5.9, 95% CI 1.9-26.3) and female sex (OR 3.0, 95% CI 1.1-8.8).

INTERPRETATION

Heparin-induced skin lesions are relatively common, have identifiable risk factors and are commonly caused by a delayed-type hypersensitivity reaction (type IV allergic response).

Lymphoplasmacytic lymphoma with Waldenstrom's macroglobulinemia as a reason for peripheral arterial perfusion disorders

Peripheral arterial perfusion disorders are often caused by embolism and thrombosis induced by diseases of the cardiovascular system. We report about a case of a 42-year-old female with peripheral arterial perfusion disturbances of the digital arteries caused by Waldenstrom s disease due to high plasma viscosity. Our patient presented with elevated plasma viscosity (1.34 mPA) and therefore plasmapheresis was necessary. Plasma separation is the most effective acute treatment for symptomatic hyperviscosity syndrome. In a second step patients with clinical symptoms of M. Waldenstrom have to be treated by chemotherapy.

Response to aspirin and clopidogrel monitored with different platelet function methods

Laboratory non-response to aspirin or clopidogrel is defined as an inability to cause in vitro detectable platelet function inhibition. It would be beneficial to monitor response to aspirin or clopidogrel with widely available and routinely used platelet function methods, like the platelet function analyzer (PFA-100) or the fully automated coagulation analyzer BCT. The aim of this study was to assess the potential of the coagulation analyzer BCT and the platelet function analyzer PFA-100 in monitoring the response of aspirin and clopidogrel. A group of 125 consecutive patients with arterial occlusive disease treated either with aspirin 100 mg/day (82 patients) or clopidogrel 75 mg/day (43 patients) as only antiplatelet drug were investigated. For the first time platelet-enriched plasma (PRP), not adjusted to a fixed predetermined concentration of platelets, was used for aggregation studies and the effect of clopidogrel alone without combination of aspirin treatment on platelet function was investigated. Response to aspirin was observed in 85% (70/82) of patients using PFA-100, while performing the arachidonic acid-induced aggregation on the BCT showed an inhibitory effect to aspirin in 91% (75/82) of patients. Non-response to aspirin was assessed with both platelet function methods in 7% (6/82) of patients. Clopidogrel response was observed in 58% (25/43) of patients when performing ADP-induced aggregation on the BCT. On the PFA-100 the antiplatelet effect of clopidogrel could not be detected. In conclusion, measurement of platelet aggregation on the BCT using native platelet-enriched plasma allows the quantification of individual inhibitory effects to aspirin as well as to clopidogrel, while the PFA-100 seems only suitable to investigate the degree of platelet inhibition induced by aspirin but not by clopidogrel.

[Update thrombophilia]

A survey on definitions, epidemiology, clinical manifestations of congenital and acquired thrombophilias is given with focus on evidence-based data. Diagnostic and therapeutical strategies are presented. Selective thrombophilia screening based on previous personal and/or family history of venous thromboembolism is more cost-effective than universal screening in all patient groups. In the majority of patients with venous thrombosis the results of thrombophilia screening do not influence the duration of oral anticoagulation. The only patient population who clearly profits from thrombophilia screening in this situation are patients with a newly diagnosed antiphospholipid syndrome, because prolonged anticoagulation can avoid the high incidence of recurrence in this patient population. Because of the increased risk of venous thrombosis during pregnancy and the puerperium, thrombophilia screening is indicated in selected patients with a previous history of venous thrombosis to be able to decide whether anticoagulation is necessary when these patients become pregnant. Significant associations with early and late pregnancy loss are observed for patients with thrombophilia while it remains unknown whether these patients profit from anticoagulation with heparin or low dose aspirin during their next pregnancy since placebo-controlled multicenter trials are not yet available.

Hereditary and acquired thrombophilia in patients with upper extremity deep-vein thrombosis. Results from the MAISTHRO registry

The prevalence of coagulation disorders in patients with upper extremity deep-vein thrombosis (UE-DVT) is unknown due to only a few observational studies of limited size reporting varying results. Therefore, we aimed to evaluate the prevalence of thrombophilia in patients with UE-DVT compared to patients with lower extremity deep vein thrombosis (LE-DVT). One hundred fifty consecutive patients (15 to 91 years of age) with UE-DVT were recruited from the MAISTHRO (MAin-ISar-THROmbosis) registry. Three hundred LE-DVT patients matched for gender and age served as controls. Thrombophilia screening included tests for the factor V Leiden mutation, the prothrombin G20210A mutation, antiphospholipid antibodies and factor VIII (FVIII), protein C, protein S and antithrombin activities. At least one thrombophilia was present in 34.2% of UE-DVT and 39.2% in UE-DVT that was unrelated to venous catheters relative to 55.3% in LE-DVT patients (p<0.001). In particular, a persistently elevated FVIII is less likely to be found in UE-DVT patients than in those with LE-DVT and is the only thrombophilia that is differentially expressed after controlling for established VTE risk factors [OR 0.46, (95% CI 0.25-0.83)]. Although less prevalent than in LE-DVT patients, thrombophilia is a common finding in patients with UE-DVT, especially in those with thrombosis that is unrelated to venous catheters.

Evidence-based indications for thrombophilia screening

Thrombophilic defects have been shown to be associated with an increased risk of venous thrombosis, fetal loss, and gestational complications. The knowledge about the clinical relevance of thrombophilic defects is increasing, and evidence-based indications for thrombophilia screening are therefore discussed in this review. Selective thrombophilia screening based on previous personal and/or family history of venous thromboembolism is more cost-effective than universal screening in all patient groups evaluated. In the majority of patients with acute venous thrombosis, the results of thrombophilia screening do not influence the duration of oral anticoagulation. The only patient population who clearly profits from thrombophilia screening in this situation are patients with a newly diagnosed antiphospholipid syndrome, because prolonged anticoagulation can avoid the high incidence of recurrence in this patient population. Because of the increased risk of venous thrombosis during pregnancy and the puerperium, thrombophilia screening is indicated in selected patients with a previous history of venous thrombosis or a positive family history. Significant associations with early and late pregnancy loss are observed for carriers of the heterozygous factor V Leiden mutation, the heterozygous prothrombin-mutation G20210A and anticardiolipin antibodies, while protein S deficiency is significantly associated with late pregnancy loss. Antithrombotic drugs like UFH, LMWH or low-dose aspirin may have a potential therapeutic benefit in patients with recurrent pregnancy loss and thrombophilia, but placebo-controlled, multicenter trials are urgently needed to clarify this issue. Although a supra-additive effect for the risk of venous thrombosis is observed between oral contraceptives and some thrombophilias, the absolute incidence of venous thromboembolism is low in premenopausal women and mass screening strategies are therefore unlikely to be effective. While antiphospholipid antibodies are known to be associated with arterial thrombosis, screening for heritable thrombophilias is not useful in arterial thrombosis, although subgroup analysis indicates that they may play a role particularly in young patients and children.

Standardization of light transmittance aggregometry for monitoring antiplatelet therapy: an adjustment for platelet count is not necessary

BACKGROUND

Light transmittance aggregometry (LTA) is considered to be the 'gold standard' of platelet function testing. As LTA has been poorly standardized, we analyzed the results of LTA in healthy subjects and patients with antiplatelet therapy using different concentrations of agonists and performing tests in non-adjusted and platelet count-adjusted platelet-rich plasma (PRP).

METHODS

LTA was performed in 20 healthy subjects and in patients treated with aspirin (n = 30) or clopidogrel (n = 30) monotherapy, as well as in patients on combination therapy (n = 20), using arachidonic acid (ARA 0.25 and 0.5 mg mL(-1)) and adenosine diphosphate (ADP 2 and 5 microm) as agonists and performing platelet function tests in non-adjusted and platelet count (250 nL(-1) +/- 10%)-adjusted PRP.

RESULTS

The overall platelet aggregation response is decreased after adjusting the PRP for platelet count compared with measurements in unadjusted PRP. The variability of aggregation results is high in adjusted PRP in the subgroup of healthy subjects, ranging from 9.2-95.3% (5th-95th percentile) relative to 77.6-95.5% in non-adjusted PRP when determining maximum aggregation to ARA 0.5 mg mL(-1). Late aggregation using ADP 2 microm ranges from 3.8-89.9% in adjusted PRP compared with 42.9-92.5% in non-adjusted PRP. Maximum aggregation using ARA 0.5 mg mL(-1) in non-adjusted PRP differentiates between aspirin-treated patients and healthy controls well, whereas late aggregation using ADP 2 microm in non-adjusted PRP offers the best discrimination between clopidogrel-treated patients and healthy controls.

CONCLUSION

Adjustment of PRP for platelet count does not provide any advantage and therefore the time-consuming process of platelet count adjustment is not necessary.

Etiology and VTE risk factor distribution in patients with inferior vena cava thrombosis

INTRODUCTION

Inferior vena cava (IVC) thrombosis is a rare event and data detailing the underlying etiology are scarce.

MATERIALS AND METHODS

Therefore, we reviewed all available cases of IVC thrombosis consecutively registered in the MAISTHRO (MAin-ISar-THROmbosis) database and described the prevalence of VTE risk factors and other conditions contributing to IVC thrombosis development.

RESULTS

53 patients (35 F, 18 M) with IVC thrombosis aged 12 to 79 years were identified. 40 patients (75.5%) developed thrombosis under the age of 45. Local problems, such as IVC anomalies or external venous compression, contributed to the development of thrombosis in 12 cases (22.6%). Lupus anticoagulants (10.9 vs. 2.3%, p=0.013) and malignoma (17.0 vs. 6.4%, p=0.023) were more prevalent in IVC thrombosis patients compared to 265 age and sex matched controls with isolated lower extremity DVT. No difference was identified with regard to inherited thrombophilia or other known VTE risk factors. Symptomatic pulmonary embolism (PE) occurred in 32.1% of IVC thrombosis patients compared to 15.2% of controls (p=0.005).

CONCLUSIONS

Local problems such as IVC anomalies and external venous compression, malignancy and the presence of lupus anticoagulants contribute to the risk of IVC thrombosis. The risk of symptomatic pulmonary embolism in the acute setting is high.

Are patients with thrombophilia and previous venous thromboembolism at higher risk to arterial thrombosis?

INTRODUCTION

Whether thrombophilic disorders, which are established risk factors for venous thromboembolism (VTE), also increase the risk of arterial thrombosis is still unknown.

MATERIALS AND METHODS

We analyzed data from 1081 consecutive patients (649 F/432 M, 16-93 years of age) with previous VTE registered in the MAISTHRO (MAin-ISar-THROmbosis) database with regard to arterial thrombotic events and contributing risk factors. Screening for thrombophilia included testing for factor V Leiden and prothrombin G20210A mutation, antiphospholipid antibodies and activities of factor VIII, protein C, protein S and antithrombin.

RESULTS

Of the entire study cohort, 40 patients (3.7%) had a prior myocardial infarction (MI), and 41 (3.8%) suffered a stroke. Other arterial thrombotic events were rare. Elevated factor VIII levels were more prevalent in MI patients than in controls (44.4 vs. 25.9%, p=0.044), but after adjusting for the traditional cardiovascular risk factors, this relationship was no longer significant. We observed a higher rate of lupus anticoagulant in MI patients with an adjusted odds ratio of 3.3 (95%CI 0.84-12.8, p=0.090). No difference in any other tested thrombophilia was observed in patients with MI or stroke relative to those without.

CONCLUSION

The cumulative incidence of arterial thrombotic events in VTE patients is low, and the inherited thrombophilias do not seem to substantially increase the risk of arterial thrombosis.

Update Thrombophilie

Es wird ein Überblick über Definitionen, Epidemiologie, Klinik der angeborenen und erworbenen Thrombophilien gegeben, wobei der Fokus auf evidenzbasierten Daten liegt. Selektives Thrombophilie-Screening, das auf einer positiven Eigen- und/oder Familienanamnese beruht, ist wesentlich kosteneffektiver als ein universelles Screening. Bei der Mehrzahl der Patienten mit venösen Thrombosen beeinflussen die Ergebnisse eines Thrombophilie-Screenings nicht die Therapiedauer mit oralen Antikoagulanzien. Die einzige Gruppe, die eindeutig von einem Screening in dieser Situation profitiert, sind Patienten mit einem Anti - phospholipidsyndrom, da bei ihnen durch eine prolongierte Antikoagulation das hohe Rezidivthromboserisiko minimiert werden kann. Da das Thromboserisiko während einer Schwangerschaft und im Wochenbett deutlich erhöht ist, kann ein Screening bei ausgewählten Patientinnen mit venösen Thrombosen in der Vorgeschichte indiziert sein, um daraus ggf. eine Indikation für eine Antikoagulation während der Schwangerschaft und im Wochenbett abzuleiten. Darüber hinaus lassen sich signifikante Assoziationen von thrombophilen Neigungen mit Früh- und Spätaborten nachweisen, wobei unklar bleibt, inwieweit Heparine oder Low-dose-Aspirin als Therapeutika bei betroffenen Frauen in einer nachfolgenden Schwangerschaft eingesetzt werden sollen, da multizentrische, placebokontrollierte Studien für diese Indikationen noch ausstehen.

[Danaparoid in pregnancy in cases of heparin intolerance - use in 59 cases]

During the use of fractionated or unfractionated heparin adverse events frequently occur that can endanger the continuation of therapy. Especially in pregnant patients with thromboembolic complications it may be difficult to find a suitable alternative anticoagulant when heparin-induced thrombocytopenia type II (HIT II) or allergic skin reactions occur. There are still limited data on the use of danaparoid in pregnancy. The main reason for heparin intolerance in the 59 reviewed pregnancies were either HIT II, described in 37/59 (62.7%) pregnancies, or cutaneous adverse effects in 19/22 (86.4%) of non-HIT-associated pregnancies (22/59, 37.3%).

RESULTS

40/59 pregnancies were carried to term under use of danaparoid and resulted in the delivery of a healthy infant. In 16/19 pregnancies, danaparoid was stopped due to a major adverse event. Five patients showed bleeding complications, seven fetal losses were documented, but there was no association with the use of danaparoid. In 31/59 (52.5%) pregnancies adverse events were documented, 14/31 (45.2%) could be attributed to danaparoid. Anti-Xa-activity was not detected in five fetal cord blood samples and in four maternal breast-milk samples.

CONCLUSION

Danaparoid can be used as an alternative anticoagulant in pregnant women with high risk for thrombosis and heparin intolerance.