Research on thrombophilic factors in arterial and venous thrombotic events: a 6-year investigation register

Abstracts

BACKGROUND: Authors report an epidemiological analysis of the investigation on thrombophilic factors in patients presenting with arterial and/or venous thrombotic events followed at the Angiology and Vascular Surgery Department at CENTERVASC, from January 2001 to January 2007. OBJECTIVE: To assess the prevalence of congenital or acquired thrombophilic markers in venous and/or arterial thrombotic events. METHODS: From January 2001 to January 2007, 224 patients with venous and/or arterial thrombotic events were screened for the presence of congenital or acquired thrombophilic markers independently of age and family history, location of thrombus and presence or absence of other thrombogenic factors. RESULTS: Thrombophilic factors were present in 112 patients (50% of the cases), in whom predominant positive results for antiphospholipid, anticardiolipin and/or lupus anticoagulant antibodies (39 cases) as well as the presence of factor V Leiden (43 cases) were observed. The venous system was the most significantly affected, and other associated thrombogenic factors were present in 56 (50%) carriers of genetic thrombophilic factors. CONCLUSION: The presence of genetic thrombophilic factors in patients with venous and/or arterial thrombotic events, independently of age or presence of other associated factors, was significant.

thrombophilia; thromboembolism; risk factors

CONTEXTO: Os autores apresentam uma análise epidemiológica sobre a investigação de marcadores de trombofilia em pacientes que apresentaram eventos trombóticos arteriais e/ou venosos acompanhados no Departamento de Angiologia e de Cirurgia Vascular do CENTERVASC no período de janeiro de 2001 a janeiro de 2007. OBJETIVO: Avaliar a prevalência de marcadores de trombofilias congênitas ou adquiridas nos eventos trombóticos venosos e/ou arteriais. MÉTODOS: Entre janeiro de 2001 e janeiro de 2007, 224 pacientes com eventos trombóticos venosos e/ou arteriais foram submetidos a uma rotina de investigação quanto à presença ou não de marcadores de trombofilia, independentemente da idade e história familiar dos pacientes, topografia do evento e presença ou ausência de fatores trombogênicos extrínsecos. RESULTADOS: Foram detectados marcadores de trombofilia em 112 pacientes (50% dos casos). Nestes, observou-se de modo predominante a positividade para anticorpos antifosfolipídios, anticardiolipina e/ou anticoagulante lúpico (39 casos), bem como a presença do fator V de Leiden (43 casos). O sistema venoso foi significativamente o mais acometido, e a ocorrência associada com condições trombogênicas extrínsecas esteve presente em 56 (50%) dos portadores de marcadores de trombofilias. CONCLUSÕES: A presença de marcadores de trombofilia nos pacientes com eventos trombóticos, venosos e/ou arteriais, independentemente da faixa etária ou da existência de fatores extrínsecos associados, foi significativa.

Trombofilia; tromboembolismo; fatores de risco

ORIGINAL ARTICLE

Research on thrombophilic factors in arterial and venous thrombotic events: a 6-year investigation register

Marcos Arêas Marques^I; Paulo Roberto Mattos da Silveira^II; Arno von Ristow^III; Marcus Gress^IV; Alberto Vescovi^IV; Bernardo Massière^IV; José Mussa Cury Filho^IV

^IChefe, Departamento de Angiologia, Centro Integrado de Prevenção, Diagnóstico e Tratamento Vascular (CENTERVASC), Rio de Janeiro, RJ, Brazil. Professor colaborador, Universidade do Grande Rio Professor José de Souza Herdy (UNIGRANRIO), Duque de Caxias, RJ, Brazil. Membro, Conselho Científico, SBACV

^IIDoutor, Medicina, Universidade Federal de São Paulo – Escola Paulista de Medicina (UNIFESP-EPM), São Paulo, SP, Brazil. Professor associado, Pós-Graduação em Cirurgia Vascular e Endovascular, Pontifícia Universidade Católica do Rio de Janeiro (PUCRJ), Rio de Janeiro, RJ, Brazil

^IIIDiretor médico, CENTERVASC, Rio de Janeiro, RJ, Brazil. Professor associado, Pós-Graduação em Cirurgia Vascular e Endovascular, PUCRJ, Rio de Janeiro, RJ, Brazil

^IVCirurgião vascular, CENTERVASC, Rio de Janeiro, RJ, Brazil

Correspondence

ABSTRACT

Background: The authors report an epidemiological analysis of the investigation on thrombophilic factors in patients presenting arterial and/or venous thrombotic events followed at the Angiology and Vascular Surgery Department at CENTERVASC, from January 2001 to January 2007.

Objective: To assess the prevalence of congenital or acquired thrombophilic factors in venous and/or arterial thrombotic events.

Methods: From January 2001 to January 2007, 224 patients with venous and/or arterial thrombotic events were screened for the presence of congenital or acquired thrombophilic factors independently of age and family history, location of thrombus and presence or absence of other thrombogenic factors.

Results: Thrombophilic factors were present in 112 patients (50% of the cases), in whom predominant positive results for antiphospholipid, anticardiolipin and/or lupus anticoagulant antibodies (39 cases) as well as the presence of factor V Leiden (43 cases) were observed. The venous system was the most significantly affected, and other associated thrombogenic factors were present in 56 (50%) carriers of genetic thrombophilic factors.

Conclusion: The presence of genetic thrombophilic factors in patients with venous and/or arterial thrombotic events, independently of age or presence of other associated factors, was significant.

Keywords: Thrombophilia, thromboembolism, risk factors.

Introduction

Congenital thrombophilias

Decreased antithrombin (AT) plasma levels were the first genetic deficiency of a natural anticoagulant associated with deep vein thrombosis (DVT). Described by Egeberg in 1965,¹ AT, the primary heparin cofactor, is an important protease-inhibitor enzyme, helping to regulate the function of various proteins involved in the coagulation cascade. Its primary function is producing the physiological inhibition of thrombin (factor IIa) and factor Xa, but it is also involved in the inhibition of activated factors IX, XI and XII, as well as kalikrein and plasmin.² In 1981, Griffin et al. first reported that protein C (PC) deficiency in humans leads to a state of hypercoagulability.³ PC is a vitamin K-dependent protein, active in the coagulation cascade, which basically inactivates active cofactors V and VIII, resulting in the natural inhibition of thrombin production, thus justifying the fact that its deficiency may lead to a prothrombotic state. One peculiarity is warfarin-induced skin necrosis, found in individuals with PC deficiency who start using vitamin K antagonists without concurrent heparin use.³ The phenomenon is a consequence of decreased PC plasma levels before the decrease in vitamin K-dependent coagulation factors (factors VII, IX, X and II), leading to a state of momentary hypercoagulability. The situation leads to microvascular skin thrombosis, which may cause skin ulcers throughout the body (Figure 1).

Homozygotic PC deficiency is rare (one in every 500,000-750,000 births)³ and may lead to a syndrome known as neonatal purpura fulminans. The association between congenital protein S (PS) deficiency and thromboembolic events was first identified in 1984.⁴ Protein S is an enzymatic cofactor of activated PC in the proteolytic degradation of activated cofactors VI and VIII.⁵ Homozygotic PS deficiency is rare and, like PC deficiency, may lead to neonatal purpura fulminans.

Em 1993, Dahlback et al. described a new, frequent form of thrombophilia, known as congenital activated protein C resistance (APCR).⁶ In 95 percent of cases, APCR is secondary to a specific genetic defect, G-A mutation at nucleotide 1691 of the coagulation cofactor V gene. The mutation is a consequence of replacing arginine (R) with glutamine (Q) at position 506 of the protein, generating a mutant cofactor V known as factor V Leiden (FVL), the most common cause of congenital thrombophilia.⁶ Described in 1996 by Poort et al.,⁷ the mutation of the prothrombin gene probably arose 24,000 years ago,⁸ when G was replaced by A at nucleotide 20210 in the 3' untranslated region of the prothrombin gene (coagulation factor II). The discovery of these two mutations (FVL and FIIG20210A) enabled a significant increase in proven etiological diagnoses of thromboembolic events,⁹ as well as provided an incentive to determine a standard for investigating the etiopathogeny of such episodes.

Studies suggest higher homocysteine plasma levels may be a modifiable risk factor for cardiovascular diseases and thromboembolic phenomena, due to their possible harmful effect on the endothelium.¹⁰

Hyperhomocysteinemia may be caused by genetic enzymatic deficiencies associated or not with nutritional disorders. Mild and moderate increases in homocysteine (serum levels between 15 and 100 μM/L) are usually found in normal individuals who are carriers of heterozygotic deficiency of enzymes cystathionine β-synthetase or methylene tetrahydrofolate reductase, found in up to 1.5 percent of the population.¹¹

Acquired thrombophilias

Various clinical scenarios may be associated with AT, PC and OS deficiencies, both because of deficient synthesis and due to excessive consumption or loss. The conditions include: hepatopathy, malnutrition, heparin therapy, use of vitamin K antagonists, nephrotic syndrome, prematurity, extensive burns, inflammatory bowel disease, thrombotic microangiopathy, neoplasms, disseminated intravascular coagulation, sepsis, pregnancy, chemotherapy, and recent thrombotic events.^2-5

Antiphospholipid antibody syndrome (APS) is an autoimmune systemic disorder, characterized by the occurrence of arterial and/or venous thrombosis, fetal death and recurrent miscarriages, followed by high titers of antiphospholipid antibodies, especially lupus anticoagulant, anticardiolipin antibody (IgM and IgG), and anti-β2-glycoprotein I antibodies (IgM and IgG).¹²

Hyperhomocysteinemia is usually found among patients suffering from deficient nutritional intake of pyridoxine (vitamin B6), cyanocobalamine (vitamin B12) and folic acid. Other conditions that may lead to increases in homcysteine plasma levels include: chronic renal failure, hyperthyroidism, inflammatory bowel disease, rheumatoid arthritis, organ transplants, and drug use (anticonvulsants, L-Dopa, methotrexate, trimethropim, nitrous oxide, and ciclosporin). Hyperhomocysteinemia can also be acquired from habits such as smoking, excessive coffee or tea consumption, and strict vegetarianism. Age is another determining factor, due to decreased vitamin B12 intake caused by atrophic gastritis in the elderly.

Criteria for investigation

It is important to consider that the vascular system (venous and/or arterial) in which the thrombotic event takes place, since it implies distinct physiopathological mechanisms, with likewise distinct prognoses and treatments. In 2005, the International Consensus Statement on Thrombophilia and Venous Thromboembolism¹³ suggested thrombophilia should be investigated under the following conditions:

a) for all patients suffering their first episode of spontaneous thromboembolism;

b) episode of thromboembolism before the age of 50 even with transient risk factors;

c) thromboembolism secondary to pregnancy, use of oral contraceptives or hormone replacement therapy;

d) recurrent thromboembolism, independent of other risk factors;

e) recurrent superficial thrombophlebitis, in the absence of neoplasms or varicose veins;

f) thromboembolism in unusual locations, such as cerebral venous thrombosis, hepatic and mesenteric venous thrombosis, and central retinal vein thrombosis before the age of 50;

g) warfarin-induced skin necrosis and neonatal purpura fulminans unrelated to sepsis;

h) asymptomatic first-degree relatives of symptomatic thrombophilia patients, especially women of childbearing age;

i) two consecutive or three nonconsecutive abortions independently of gestational age or fetal death after 20 weeks' gestation;

j) severe preeclampsia;

l) thromboembolism in children.

At first, laboratory investigation should be performed under all scenarios described above which may lead to suspicion of thrombophilia, using functional count of coagulation inhibitors (AT, PC, PS), plasma homocysteine count, analysis of mutations (FVL and FIIG20210A), and assessment of presence of antiphospholipid antibodies (lupus anticoagulant, anticardiolipin IgM and IgG).

There are relevant aspects which should, whenever possible, be taken into consideration to enable a more systematic etiological investigation of thrombophilia:

a) individuals diagnosed as thrombophilic should be required to be submitted to thrombosis prophylaxis in risk situations;

b) the presence of associations of thrombophilic defects imply greater thrombogenic potential, demanding greater vigilance of its carrier;

c) demonstrating the presence or absence of antiphospholipid antibodies provides guidelines regarding time frame and intensity of anticoagulation in patients suffering a thromboembolic event;

d) the identification of a congenital thrombophilic defect justifies extending the investigation to relatives, in search of asymptomatic carriers who could then receive proper information in risk situations.

Methods

The study comprehended the period from January 2001 through January 2007. The presence of thrombophilic factors was investigated in 224 patients (130 women and 94 men) who presented venous and/or arterial thrombotic events independently of topography. The investigative routine included FVL and FIIG20210A analysis through the polymerase chain reaction (PCR) method at any moment of the thrombotic event and independently of the use of anticoagulants.

AT deficiency was investigated using the colorimetric method with a synthetic chromogenic substrate for functional AT, while PC and PS deficiencies using the colorimetric method with a synthetic chromogenic substrate for functional PC and PS. AT, PC and PS dosages were always done at least 30 days after the end of oral anticoagulation treatment with sodium warfarin.

IgM and IgG anticardiolipin antibodies were investigated using the ELISA method, according to the standards from the international consensus statement updating the criteria of definition for APS, published in 2006.¹⁴

The presence of a lupus anticoagulant was detected through the extension of one of the following tests: activated partial thromboplastin time, dilute Russell's viper venom time, and thromboplastin inhibition time.

Serum homocysteine dosage was assessed after 12-hour fasting, using the HPLC (high performance liquid chromatography) method.

Except for FVL and FIIG20210A research, all tests that came back positive were repeated to rule out false positives.

All thrombotic events were confirmed by complementary imaging tests (color Doppler ultrasonography, magnetic angiographic resonance or computed angiographic tomography).

Results

Of the 224 patients surveyed, 112 (50%) had positive results for thrombophilic factors in laboratory tests, thus representing object of analysis for this study. Of the 112 carriers of thrombophilic factors, 61 (54.46%) were female and 51 (45.54%) male, average age 48.11 years (16-81 years old). Ninety-seven (86.6%) thrombotic events took place in the venous system, while 14 (12.5%) did so in the arterial system. Only one case (0.9%) involved the compromise of both systems.

Of the 97 venous thrombotic events, 90 (92.78%) took place in the lower limbs, with rare manifestations in other parts (Figure 2), while six (42.86%) of the 14 arterial events took place in other locations (carotid arteries, upper limbs, central nervous system, retina).

Associated extrinsic thrombogenic factors were found in 56 patients (50%): surgery (17 cases), autoimmune diseases (nine cases), prolonged immobilization (eight cases), estrogen use (eight cases), puerperium (two cases), neoplasia (three cases), and other risk factors (six cases: alcoholism, thrombocytosis, systemic hypertension, and smoking). Three patients had two concurrent risk factors. The remaining 56 patients in the subgroup (50%) had thrombosis without any clinically identifiable predisposing factor, representing the so-called "spontaneous thrombosis".

The incidence of thrombophilic factors in the 112 cases is depicted in Table 1, having been diagnosed in 101 patients (90.18%) in isolation and in 11 patients (9.82%) in association. In terms of the relationship between type of thrombophilic factor and location of thrombotic event (venous, arterial or mixed), we notice that, in the venous system, FVL and APS (predominantly the anticardiolipin antibody) were present in 71 events (65.74%) of thromboembolism attributable to the existence of thrombophilia (Figure 3). In turn, in the arterial system, the presence of the anticardiolipin antibody was widely dominant (62.5%) over other thrombophilic alterations (Figure 4). We should also highlight hyperhomocysteinemia and prothrombin mutation, contributing in both alterations over 10 percent to the incidence of thrombosis among thrombophilic patients. Familial antecedents for thrombophilia were found in 21 cases (25%).

Discussion

Thromboembolic disease has multifactorial etiology, resulting from the complex interaction between genetic and environmental factors, affecting both the arterial and the venous systems.¹⁵

In the present study, we detected a significant prevalence of thrombophilia among patients who had thrombotic events in the venous or arterial systems, or even, though less frequently, in both, without significant predominance in an age range considered young (below the age of 40). Of the 112 patients positive for thrombophilic factors, 67 percent were older than 40, and 25.89% were older than 60. Medical literature stresses that over 50 percent of patients who suffer a thrombotic event have some defect, whether congenital or acquired, in a platelet or coagulation protein, generating a state of hypercoagulability, possibly leading to thrombosis, especially when associated with extrinsic factors or predisposing clinical conditions.¹⁶

The predominance of FVL and antiphospholipid antibodies as thrombophilic conditions over coagulation inhibitor deficiencies has been duly proved in various studies. FVL prevalence is as high as 7 percent among whites,⁶ while antiphospholipid antibody prevalence can be of over 20 percent among patients with DVT,¹⁷ the presence of antiphospholipid antibodies being five times more common than that of lupus anticoagulant.¹⁸

The greater frequency of venous system thrombosis in thrombophilia cases, especially DVT in the lower limbs, has been found by various epidemiological studies. From 30 to 50 percent of DVT patients have congenital coagulation protein defects, while circa 28 percent have APS.¹⁷ This fact has been interpreted as meaning that the mechanism of thrombus formation in the venous system differs from that in the arterial. While thrombosis by alteration of the coagulation cascade is predominant in the first, in the second, the starting point of thrombogenesis is the adhesion and aggregation of platelets. Since thrombophilic changes induce more changes to the coagulation cascade than to platelet activity, this explains the predominance of venous thrombosis over arterial thrombosis in surveys of thrombophilia. As stated above, the most common thrombotic event is that found in the venous system of the lower limbs, but involvement in other parts, such as mesenteric, renal, hepatic, portal, and cava veins, is also described.¹⁹ Arterial events are rares in defects of coagulation proteins; in APS, however, especially in the primary presence of anticardiolipin antibodies (with underlying clinical comorbidities), arterial events can be almost as common as venous ones,²⁰ as opposed to the presence of primary lupus anticoagulant, for which the most frequent manifestation is DVT.¹⁸ This differentiation was also present among the patients analyzed: eight cases of arterial thrombosis were found in patients positive for anticardiolipin antibodies, versus a single case in a patient positive for lupus anticoagulant.

The fact that thrombosis recurs in approximately one third of patients diagnosed as thrombophilic and that familial antecedents for thrombosis were registered in over 25 percent of cases in this study shows the importance of prophylaxis for thrombophilic patients in risk situations,²¹ as well as the relevance of identifying prothrombotic alterations in blood relatives, so that they may also be subjected to the same preventive measures to avoid the negative consequences of abnormal coagulation.

A more systematic inquiry into cases of thrombotic events would allow for more information about the etiopathogeny and the aggressiveness of such thrombophilias, thus enabling sounder decisions regarding the duration of treatment with anticoagulants, the need for testing relatives²² (both parents and children) , and adequate prophylaxis for effectively preventing thrombotic events, dramatically increasing the odds of reducing the morbidity and mortality caused by such thrombotic events.

The following could be arguments against regularly testing thrombophilic factors in thrombotic events: a) the fact that thromboembolic disease has multifactorial etiology and that the presence of thrombophilic factors should not be be considered as the only factor in its etiopathogeny, but only a contributing one; b) laboratory tests for some thrombophilic factors lack universal standardization; and c) testing thrombophilic factors is costly both for public and private health systems, and their cost-benefit ratio has yet to be accurately assessed.

Conclusion

In this study, the presence of genetic thrombophilic factors in patients with venous and/or arterial thrombotic events, independently of age or presence of other associated factors, was significant.

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Publication Dates

• Publication in this collection
  05 Jan 2010
• Date of issue
  Sept 2009

History

• Accepted
  22 July 2009
• Received
  25 Mar 2008