Argyri Gialeraki

VKORC1 and CYP2C9 allelic variants influence acenocoumarol dose requirements in Greek patients

AIM To identify the frequencies of the polymorphisms CYP2C9*2, CYP2C9*3 and VKORC1-1639 G>A in the Greek population and investigate whether these polymorphisms and patient demographics (age, sex and comedication) could explain the interindividual variability of acenocoumarol dose requirements for efficient anticoagulation. MATERIALS & METHODS CYP2C9*2 (Arg144Cys), CYP2C9*3 (Ile359Leu) and VKORC1-1639G>A allelic variants were analyzed in 98 patients treated with acenocoumarol. RESULTS Allelic frequencies of CYP2C9*2, CYP2C9*3 and VKORC1A were found to be 0.155, 0.075 and 0.485, respectively. Carriership of at least one CYP2C9*3 allele led to the most pronounced reduction in the required mean dose (p<0.0001). In contrast, the CYP2C9*2 allele played a minor role (p=0.3). VKORC1 A/A patients needed approximately a third of the dose required by wild-type patients to achieve the target INR (p<0.0001). Age was the only demographical factor significantly affecting acenocoumarol dose (p<0.0001). In a multivariable regression model, CYP2C9, VKORC1 genotypes and age explained 55% of acenocoumarol dosing variability. CONCLUSION VKORC1-1639G>A, CYP2C9*2 and CYP2C9*3 polymorphisms were found to predispose to acenocoumarol sensitivity in Greeks. Other hereditary and nongenetic parameters must be incorporated in an individualized dosing algorithm to achieve a safer anticoagulant effect.

Prevalence of Prothrombotic Polymorphisms in Greece

The aim of this study was to assess the prevalence of several polymorphisms in genes that are involved in several pathways such as hemostasis, fibrinolysis, platelet membrane receptor activity, endothelial integrity and function, lipid metabolism, and regulation of blood pressure in healthy subjects of Greek origin. Most of these polymorphisms are mainly associated with conditions such as venous thromboembolism and atherothrombosis, and their prevalence has not been studied yet in Greece. We tested 140 healthy individuals for factor V (FV)1691G/A, FV4070G/A, FII 20210G/A, factor XIII (FXIII) exon 2G/T, fibrinogen beta-455G/A, plasminogen activator inhibitor-1 (PAI-1)-675 4G/5G, human platelet antigens 1 (HPA1) a/b, apolipoprotein B (ApoB) 10708 G/A, apolipoprotein E (ApoE) E2, E3, and E4, angiotensin-converting enzyme (ACE) D/I, 5,10 methylenetetrahydrofolate reductase (MTHFR) 677C/T, and MTHFR 1298A/C polymorphisms using a PCR and reverse hybridization technique that detects all of them simultaneously. The allele frequencies observed are in accordance with those reported in other Caucasian populations and almost identical to those of East Mediterranean populations. This first report from Greece may serve as a baseline for planning further investigations of these polymorphisms in association with several clinical entities and for launching guidelines for patient testing of various disease settings in this population.

Thrombomodulin as a regulator of the anticoagulant pathway: implication in the development of thrombosis.

Thrombomodulin is a cell surface-expressed glycoprotein that serves as a cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell PC receptor. The PC pathway is a major anticoagulant mechanism that downregulates thrombin formation and hedges thrombus formation. The objectives of this review were to review recent findings regarding thrombomodulin structure, its involvement in the regulation of hemostasis and further discuss the implication, if any, of the genetic polymorphisms in the thrombomodulin gene in the risk of development of thrombosis. We performed a literature search by using electronic bibliographic databases. Although the direct evaluation of risk situations associated with thrombomodulin mutations/polymorphisms could be of clinical significance, it appears that mutations that affect the function of thrombomodulin are rarely associated with venous thromboembolism. However, several polymorphisms are reported to be associated with increased risk for arterial thrombosis. Additionally studies on knock out mice as well studies on humans bearing rare mutations suggest that thrombomodulin dysfunction may be implicated in the pathogenesis of myocardial infraction.

Resistance to activated protein C and FV Leiden mutation in patients with a history of acute myocardial infarction or primary hypertension

This study was designed to investigate both resistance to activated protein C (APC-R) and the factor FV Q506 mutation incidence in patients with a history of acute myocardial infarction (AMI) and patients with primary hypertension (PH), a high-risk group for arterial thrombosis. Eighty patients with a history of AMI (group A), 160 patients with a history of PH (group B), and 124 age-matched controls without arterial disease (group C) were studied. APC-R was determined using the Coatest APC Resistance Kit of Chromagenix, Sweden. The prevalence of the FV Q506 mutation was estimated by DNA analysis (Bertina method). The prevalence of the FV Q506 mutation was 20%, 13.75%, and 8% in groups A, B, and C, respectively (A v C P = .0466). The prevalence of APC-R was 47.5% in group A v 13% in group C (P < .0001) and 36.25% in group B v 13% in group C (P < .0001). The response to activated protein C expressed as mean value +/- SD was 2.05 +/- 0.33 in group A v 2.56 +/- 0.46 in group C (P < .05) and 2 +/- 0.22 in group B v 2.56 +/- 0.46 in group C (P < .05). These findings suggest that patients with a history of AMI or PH have a significantly increased incidence of both APC-R and FV Q506 mutation compared with the control group. These findings support the hypothesis that these anticoagulant defects may be risk factors for arterial thrombosis.

Circadian pattern of symptoms onset in patients ≤35 years presenting with ST-segment elevation acute myocardial infarction

BACKGROUND There are scarce data regarding the circadian pattern of symptoms onset in young patients presenting with acute myocardial infarction (AMI). We explored whether young patients with ST-segment elevation AMI exhibit a circadian variation in symptoms onset. METHODS We recruited prospectively 256 consecutive patients who had survived their first ST-segment elevation AMI ≤35 years of age. Patients were categorized into 4 groups by 6-h intervals over 24 h. RESULTS In 49 patients (19.1%) the clinical presentation of AMI was atypical. The symptoms onset was as follows: 00:01 to 06:00, 19.1%, 06:01 to 12:00, 32.4%; 12:01 to 18:00, 28.1%; and 18:01 to 24:00, 20.3%. There was a significant association between the time of day and the likelihood of symptoms onset (Rayleigh test, p<0.001). Between 00:01 and 06:00 the incidence of AMI onset was lower than expected and between 06:01 and 12:00 was higher (p=0.034 and p=0.011, respectively), whereas in the other 6-h period groups no difference was found between expected and observed AMI incidence (p=0.280 and p=0.131). No significant differences were found regarding clinical characteristics, i.e. traditional risk factors, reperfusion treatment of AMI, ejection fraction of left ventricle, time interval from pain onset to hospital arrival, dietary habits and physical activity, among the 6-h period groups. CONCLUSIONS ST-segment elevation AMI in individuals ≤35 years of age follows a circadian pattern with a morning peak. This information might be useful for the prompt diagnosis and treatment of AMI in very young patients which occurs rarely and frequently with atypical clinical presentation.

Do different substitution patterns or plant origin in hydroxyethyl starches affect blood coagulation in vitro

The effect of hydroxyethyl starches (HES) on blood coagulation is affected by their molecular weight, their molar substitution and the C2/C6 ratio. The solutions of 6% HES 130/0.4 and 6% HES 130/0.42 have similar molecular weight and molar substitution but different C2/C6 ratio and plant origin. In the present study, the comparative effect of 6% HES 130/0.4 versus 6% HES 130/0.42 on blood coagulation was investigated in vitro. Thirty milliliter of blood was obtained from 10 healthy volunteers and was diluted by 10, 30 and 50% using either 6% HES 130/0.4 or HES 130/0.42, respectively. Blood coagulation was assessed using thrombelastography measurements (clotting time, clot formation time, maximal clot firmness and alpha-angle). The assessment of platelet function was performed with whole blood aggregometry after adding thrombin–receptor-activating protein. No differences were noted between respective dilutions of the two HES. Both colloids produced significant reductions below the reference values range in clotting time at 10, 30 and 50% dilutions. The 50% dilution of both colloids resulted in significant reduction of maximal clot firmness, alpha-angle and platelet aggregation. The present study showed that the corn-derived 6% HES 130/0.4 and the potato-derived 6% HES 130/0.42 have the same effect on blood coagulation in vitro.

Retinal vein occlusion: genetic predisposition and systemic risk factors.

The role of systemic risk factors (age, smoking, diabetes, arterial hypertension) in the development of retinal vein occlusion (RVO) is well established. However, the association of RVO with genetic predisposition to thrombosis remains poorly understood. The aim of the study was to assess any possible additional effect of genetic predisposition to the already well known ‘classical’ risk factors of RVO in a cohort of elderly Greek patients. Fifty-one elderly patients with RVO and 51 healthy individuals matched for age and sex were evaluated for systemic risk factors (smoking, diabetes, dyslipidemia, arterial hypertension) and coagulation defects (lupus anticoagulant, natural inhibitors of coagulation). Additionally, genotyping was performed for mutations/polymorphisms involved in haemostasis such as: FV G1691A, FV G4070A, FIIG 20210A, MTHFR C677T and A1298C, PAI-1-675 4G/5G, F XIII exon 2G/T, EPCR A4600G and G4678C. We identified systemic risk factors in the majority of the patients Hypertension (P = 0.001), dyslipidemia (P = 0.029) and diabetes (P = 0.01) are associated with RVO in the majority of the patients. The prevalence of prothrombotic risk factors was not significantly different in the patients with RVO compared to controls. Apart from systemic risk factors, genetic predisposition to thrombosis does not seem to have an important association with RVO in this group of elderly patients.

Evaluation of a reverse-hybridization StripAssay for the detection of genetic polymorphisms leading to acenocoumarol sensitivity

Acenocoumarol is mainly catabolized by CYP2C9 isoform of cytochrome P450 (CYP) liver complex and exerts its anticoagulant effect through the inhibition of Vitamin K Epoxide Reductase (VKOR). The most important genetic polymorphisms which lead to an impaired enzymatic activity and therefore predispose to acenocoumarol sensitivity, are considered to be CYP2C9*2 (Arg144Cys), CYP2C9*3 (Ile359Leu) and VKORC1-1639G>A, respectively. In this study we compared the results of the PGXThrombo StripAssay kit (ViennaLab Diagnostics,Vienna, Austria) with direct DNA sequencing and in house Restriction Fragment Length Polymorphisms (RFLP) for the detection of the aforementioned Single Nucleotide Polymorphisms (SNPs). The reverse hybridization StripAssay was found to be equally effective with RFLP and direct DNA sequencing for the detection of CYP2C9*2 and CYP2C9*3 polymorphisms, respectively. The comparison of the RFLP reference method with the reverse hybridization StripAssay for the detection of VKORC1-1639 G>A polymorphism showed that the reverse hybridization StripAsssay might misclassify some A/A homozygotes as heterozygotes. Optimization of the hybridization procedures may eliminate the extra low signal band observed in some samples at the reverse hybridization StripAssay and improve its diagnostic value.

Central Retinal Vein Occlusion Secondary to Clomiphene Treatment in a Male Carrier of Factor V Leiden

We report a case of a 35-year-old previously healthy man treated with clomiphene for infertility, who presented with blurred vision in his left eye due to ocular vein occlusion as documented by fluorescein angiography. The patient was heterozygous for the factor V Leiden (FV Leiden) mutation and for the 1298 A-C polymorphism of the methylene-tetrahydrofolate reductase (MTHFR) gene. He was treated with clopidogrel and is now free of symptoms. Because congenital thrombophilia is a moderate risk factor for central retinal vein occlusion and the administration of clomiphene may trigger this process, we recommend screening of young patients for FV Leiden before clomiphene treatment.

Oral Contraceptives and HRT Risk of Thrombosis.

Estrogen-containing medication, prescribed either for contraception in women of reproductive age or for prevention of cardiovascular events and osteoporosis as well as for alleviation of symptoms related to menopause, is associated with changes in the hemostatic balance and contributes to increased risk of development of venous thromboembolic complications. This risk is dose and medication dependent, increases with age, congenital and/or acquired predisposition to thrombosis, and mode of administration. This review attempts to summarize the current knowledge regarding the pathophysiology of oral contraceptive (OC) and hormone replacement therapy (HRT) -induced prothrombotic state in women, the risk of thrombosis associated with administration of various commercially available OCs and HRT, the additional risk in women with hereditary or acquired thrombophilia, and the currently available recommendations regarding massive screening of women for thrombophilia prior to initial prescription or continuation of treatment with OCs and HRT preparations.