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Keywords:

  • cardiovascular disease;
  • F5 R506Q (factor V Leiden) and F2 G20210A (prothrombin G20210A);
  • thrombophilia;
  • epidemiology

F5 R506Q (factor V Leiden) and F2 G20210A (prothrombin G20210A) are risk factors for venous thrombosis (Lijfering et al, 2010). The results of studies as to whether these mutations also increase the risk of cardiovascular disease (CVD) are inconsistent. A meta-analysis of 191 studies (N > 150 000) calculated a 30% increased risk of CVD among single heterozygous F5 R506Q or F2 G20210A carriers compared to non-carriers (Ye et al, 2006). Despite its large size, this study included too few double heterozygous and homozygous carriers to estimate the risk of CVD in individuals with these genetic traits. Therefore, we performed a post hoc analysis in a retrospective family cohort that contained a fairly large number of relatives who were double heterozygous or homozygous for F5 R506Q and F2 G20210A (n = 52).

Details of our study have been published previously (Bank et al, 2004, 2005; Lijfering et al, 2007). Briefly, 1641 first-degree relatives, aged 15 years or older, of consecutive patients (probands) with documented venous thrombosis or CVD before the age of 50 years and F2 G20210A, high FVIII or hyperhomocysteinaemia, were enrolled after informed consent was obtained. Information on CVD and exposure to classical cardiovascular risk factors was collected by using a standardized questionnaire and reviewing medical records. All patients were screened for F5 R506Q and F2 G20210A. Information was obtained without knowledge of the genetic status.

Observation years were defined as the years from the age of 15 until the date of inclusion or until the date of the first thrombotic event. Incidences and 95% confidence intervals (95% CIs) were calculated under the Poisson distribution assumption. Relative risks and 95% CIs of CVD were calculated in the double heterozygous/homozygous group, using single heterozygous carriers as a reference group. As we studied a thrombophilic cohort, we only compared single heterozygous F5 R506Q or F2 G20210A carriers to double heterozygous and homozygous carriers. The a-priori CVD risk for other relatives was deemed too high for inclusion as a reference group. To avoid bias, we excluded probands from the analysis.

To prevent the risk of CVD being based on relatives with cardiovascular risk factors, we intended to repeat the analysis after excluding all relatives with obesity or overweight, smoking, hypertension, dyslipidemia or diabetes mellitus. Unfortunately, as all relatives had at least one of these risk factors at the time of CVD, we were unable to do this. For similar reasons, another analysis was performed after excluding all relatives with concomitant thrombophilias.

The pedigrees of 500 probands (373 patients with objectively documented venous thrombosis, 107 patients with CVD and 20 patients with both venous thrombosis and CVD) disclosed 1641 first-degree relatives aged 15 years or older. Of these relatives, 45 were not evaluable because of missing laboratory data and 1149 were non-carriers of F5 R506Q or F2 G20210A (8% of whom had a cardiovascular event). The remaining 447 relatives were analysed: 175 were single heterozygous for F5 R506Q, 220 were single heterozygous for F2 G20210A, 37 were double heterozygous for F5 R506Q and F2 G20210A, eight were homozygous for F5 R506Q and seven were homozygous for F2 G20210A. The clinical characteristics are summarized in Table I. Males and females were distributed equally. The median age at inclusion was 47 years (range, 15–91). Concomitant thrombophilias were found in approximately 60% of all relatives.

Table I.   Clinical characteristics.
 Heterozygous F5 R506Q–F2 G20210A or Homozygous F5 R506Q or F2 G20210ASingle heterozygous F5 R506Q or F2 G20210A carriersTotal
  1. *No antithrombin, protein C or protein S deficiency, hyperhomocysteinaemia or high factor VIII levels.

  2. Continous variables denoted as median (range), categorical variables as number (%).

Number52 (12)395 (88)447
Male21 (40)185 (47)206 (46)
Age at enrollment (years)51 (16–85)47 (15–91)47 (15–91)
Arterial thrombosis6 (12)27 (7)33
Age at onset (years)54 (41–78)53 (26–78)53 (26–78)
Classification
 Myocardial infarction2 (4)12 (3)14 (3)
 Ischemic stroke1 (2)8 (2)9 (1)
 Transient ischaemic attack2 (4)5 (1)7 (1)
 Peripheral arterial thrombotic event1 (2)2 (0·5)3 (2)
Relatives with no other
Thrombophilic defects*21 (40)153 (39)174 (39)

During the observation period a total of 33 arterial thrombotic events occurred: 7% in single heterozygous F5 R506Q or F2 G20210A carriers and 12% in double heterozygous and homozygous carriers. The median age at onset was similar in both groups (53 years; range, 26–78). The annual incidence of CVD was 0·23% (95% CI, 0·13–0·79) in single heterozygous F5 R506Q or F2 G20210A carriers and 0·36% (95% CI, 0·13–0·79) in double heterozygous and homozygous carriers; relative risk 1·6 (95% CI 0·7–3·9) (Table II). After exclusion of relatives with concomitant thrombophilias, the relative risk of CVD increased to 5·1 (95% CI, 1·3–22·9) in double heterozygous or homozygous F5 R506Q and F2 G20210A carriers compared to single F5 R506Q or F2 G20210A carriers.

Table II.   Risk of cardiovascular disease in relatives of probands with a thrombophilic defect.
 Observation yearsRelatives with eventAnnual incidence % (95% CI)Crude relative risk (95% CI)
All evaluable relatives
 Single heterozygous F5 R506Q or F2 G20210A carriers11 854270·23 (0·15–0·33)References
 Double heterozygous or homozygous F5 R506Q or F2 G20210A164660·36 (0·13–0·79)1·60 (0·66–3·88)
Relatives with concomitant thrombophilias excluded
 Single heterozygous F5 R506Q or F2 G20210A carriers419940·10 (0·03–0·24)Reference
 Double heterozygous or homozygous F5 R506Q or F2 G20210A61430·49 (0·10–1·43)5·13 (1·15–22·92)

In our study, double heterozygous and homozygous F5 R506Q and F2 G20210A carriers had a 1·6-fold (95% CI, 0·7–3·9) increased risk of CVD compared to single F5 R506Q or F2 G20210A carriers. Although these results did not reach statistical significance, they further the findings of two previous studies that found a modest association between single heterozygous F5 R506Q or F2 G20210A and CVD (Ye et al, 2006; Mannucci et al, 2010), but included too few subjects to calculate, as we did, a risk in homozygous and double heterzogygous carriers.

It is unknown why, in F5 R506Q and F2 G20210A carriers, the risk of CVD appears to be more than 10 times weaker than the risk of venous thrombosis. A plausible explanation is that atherosclerosis plays a major role in CVD and a smaller role in venous thrombosis (Prandoni et al, 2003). Atherosclerosis is associated with increased endothelial damage (of which hyperhomocysteinaemia is a marker), procoagulant changes (such as high levels of FVIII) (Nordestgaard, 2009) and natural anticoagulant deficiencies (Mahmoodi et al, 2008). This could explain the observed increased relative risk of 5·1 (95% CI, 1·2–22·9) found after exclusion of relatives with concomitant thrombophilias. However, as we did not investigate whether atherosclerosis was less common in these relatives (e.g. with intima media thickness), these results should be treated with caution.

Some aspects of our study warrant comment. A strength of our study is that, due to the large cohort of thrombophilic families, it was possible to estimate the effect of double heterozygosity or homozygosity for F5 R506Q and F2 G20210A on CVD for the first time. A weakness is the retrospective design and that, despite its fairly large size, the number of double heterozygous or homozygous F5 R506Q and F2 G20210A carriers was too low to provide risk estimates with narrow confidence intervals. The number was also too low to make a subdivision of arterial thrombotic event types for additional sensitivity analyses. Another potential limitation of our study is referral bias, as this study was performed in three university hospitals. However, as we tested consecutive patients (probands), this bias was probably reduced.

In conclusion, it is likely that double heterozygous or homozygous carriers of F5 R506Q and F2 G20210A have a higher risk of CVD than single F5 R506Q or F2 G20210A carriers. However, due to small numbers, further research is required to verify our findings.

Authorship and disclosures

  1. Top of page
  2. Authorship and disclosures
  3. References

This study was funded by grant 99.187 from the Netherlands Heart Foundation. The funding organization is a public institution and had no role in the design and conduct of the study; the collection, management, analysis and interpretation of the data; or the preparation, review and approval of the manuscript. All authors have read and approved this manuscript, and state that they have no conflict of interest.

References

  1. Top of page
  2. Authorship and disclosures
  3. References
  • Bank, I., Libourel, E.J., Middeldorp, S., van Pampus, E.C., Koopman, M.M., Hamulyak, K., Prins, M.H., van der Meer, J. & Buller, H.R. (2004) Prothrombin 20210A mutation: a mild risk factor for venous thromboembolism but not for arterial thrombotic disease and pregnancy-related complications in a family study. Archives of Internal Medicine, 164, 19321937.
  • Bank, I., Libourel, E.J., Middeldorp, S., Hamulyák, K., van Pampus, E.C., Koopman, M.M., Prins, M.H., van der Meer, J. & Buller, H.R. (2005) Elevated levels of FVIII:C within families are associated with an increased risk for venous and arterial thrombosis. Journal of Thrombosis and Haemostasis, 3, 7984.
  • Lijfering, W.M., Coppens, M., van de Poel, M.H., Middeldorp, S., Hamulyak, K., Bank, I., Veeger, N.J., Prins, M.H., Buller, H.R. & van der Meer, J. (2007) The risk of venous and arterial thrombosis in hyperhomocysteinaemia is low and mainly depends on concomitant thrombophilic defects. Thrombosis and Haemostasis, 98, 457463.
  • Lijfering, W.M., Rosendaal, F.R. & Cannegieter, S.C. (2010) Risk factors for venous thrombosis – current understanding from an epidemiological point of view. British Journal of Haematology, 149, 824833.
  • Mahmoodi, B.K., Brouwer, J.L., Veeger, N.J. & van der Meer, J. (2008) Hereditary deficiency of protein C or protein S confers increased risk of arterial thromboembolic events at a young age: results from a large family cohort study. Circulation, 118, 16591667.
  • Mannucci, P., Asselta, R., Duga, S., Guella, I., Spreafico, M., Lotta, L., Angelica Merlini, P., Peyvandi, F., Kathiresan, S. & Ardissino, D. (2010) The association of factor V Leiden with myocardial infarction is replicated in 1,880 patients with premature disease. Journal of Thrombosis and Haemostasis, 8, 21162121.
  • Nordestgaard, B.G. (2009) Does elevated C-reactive protein cause human atherothrombosis? Novel insights from genetics, intervention trials, and elsewhere. Current Opinion in Lipidology, 20, 393401.
  • Prandoni, P., Bilora, F., Marchiori, A., Bernardi, E., Petrobelli, F., Lensing, A.W., Prins, M.H. & Girolami, A. (2003) An association between atherosclerosis and venous thrombosis. New England Journal of Medicine, 348, 14351441.
  • Ye, Z., Liu, E.H., Higgins, J.P., Keavney, B.D., Lowe, G.D., Collins, R. & Danesh, J. (2006) Seven haemostatic gene polymorphisms in coronary disease: meta-analysis of 66,155 cases and 91,307 controls. Lancet, 367, 651658.