Altered Fibrin Clot Properties in Patients With Cerebral Venous Sinus Thrombosis
Association With the Risk of Recurrence
Background and Purpose—Venous thromboembolism and ischemic stroke are associated with unfavorable fibrin clot structure and function. We hypothesized that denser fibrin networks displaying impaired lysability characterize patients with cerebral venous sinus thrombosis (CVST).
Methods—We assessed plasma fibrin clot properties in 50 patients (aged 38.9±9.8 years, 36 women) after the first CVST unrelated to trauma or malignancy after anticoagulation withdrawal and 50 well-matched controls. Recurrences were recorded during follow-up (18–46; median, 36 months).
Results—Clot permeability was lower in patients with CVST than in controls (Ks, 6.43±0.97 versus 7.3±1.2 10−9 cm2; P<0.001) and was associated with prolonged clot lysis time (103.0±16.8 versus 92.4±16.2 minutes; P<0.001), lower maximum rate of D-dimer release from clots (0.068 [0.064–0.071] versus 0.072 [0.067–0.078] mg/L per minute; P<0.001) and higher maximum D-dimer levels in the lysis assay (4.39±0.56 versus 4.19±0.46 mg/L, respectively; P=0.03). Patients with CVST had a slightly shorter lag phase (P=0.02) and higher maximum absorbance of fibrin gels on turbidimetry (P<0.001) compared with controls. Deficiencies in natural anticoagulants or antiphospholipid syndrome, and factor V Leiden occurred more often in the patients (P<0.05). CVST recurred in 6 patients (12%) and was associated with 21% higher baseline fibrinogen (P=0.007), 20% lower Ks (P=0.04) and 17% greater D–Dmax (P=0.01). Multiple logistic regression showed that only elevated D–Dmax (>4.83 mg/L) predicted CVST recurrence (odds ratio, 5.1; 95% confidence interval, 1.63–16.19) after adjustment for fibrinogen.
Conclusions—CVST is associated with the formation of more compact plasma fibrin clots and resistance to fibrinolysis, which may predispose to the recurrence.
Cerebral venous sinus thrombosis (CVST) is a rare disorder with an estimated annual incidence of 3 to 4 cases per 2 million adults.1 Several risk factors for CVST have been shown, including brain tumors, cancer, cerebral infections or traumas, oral contraceptive use, pregnancy, postpartum period, and thrombophilia.2–4 In 15% to 20% of patients, no predisposing factors could be identified.1 The risk of recurrent CVST is 3% and remains higher in the first year after discontinuation of anticoagulant therapy, with no association with mild thrombophilias.4
Unfavorable fibrin characteristics including faster formation of denser fibrin clots resistant to lysis represent a novel risk factor for both venous thromboembolism5 and ischemic stroke.6–8 We hypothesized that CVST is also associated with altered fibrin clot phenotype. We investigated plasma fibrin clot characteristics in patients after CVST and their impact on recurrences.
We recruited 50 consecutive adult patients with the first-ever CVST referred for thrombophilia screening (from January 2006 to June 2011) and 50 healthy controls from the hospital staff matched for age, sex, body mass index, and family history of venous thromboembolism. CVST was documented using computed tomographic angiography, magnetic resonance imaging, or magnetic resonance angiography. All the patients were treated with oral anticoagulants or low-molecular weight heparins for 6 to 12 months. The exclusion criteria were age >60 years, current anticoagulation, recent trauma, previous other thromboembolic events (deep vein thrombosis, pulmonary embolism, and myocardial infarction), severe inflammatory disorders, and malignancy.
Demographic and clinical data were recorded on the day of blood sampling.5,6,8 Follow-up started at the time of discontinuation of anticoagulant therapy and was carried out on the 6-month basis (a visit at the center or telephone contact). We recorded the objectively documented recurrence of CVST. Imaging studies were performed if clinical symptoms recurred.
The study was approved by the University Ethical Committee. The participants gave informed consent.
Fasting blood was drawn in the morning within the first 18 months since the diagnosis and at 1 to 5 months since anticoagulation withdrawal. Plasma D-dimer, plasminogen activator inhibitor-1 antigen and tissue-type plasminogen activator antigen were determined using immunoenzymatic assays (all; American Diagnostica Inc, Greenwich, CT). Thrombophilia screening was performed as described.5,6
Plasma clot permeability was assessed using a pressure-driven system and expressed as a permeation coefficient (Ks), which indicates the pore size in fibrin networks.5–7 The lag phase of the turbidity curve and the maximum absorbance at the plateau phase (ΔAbs) were recorded.5,9 Clot lysis time induced by recombinant tissue-type plasminogen activator added to plasma with tissue factor and phospholipids was determined.9 Moreover, D-dimer levels during tissue-type plasminogen activator–induced lysis were measured in the effluent up to the collapse of the plasma gel and maximum rate of increase in D-dimer (D–Drate) with maximum D-dimer concentrations (D–Dmax) were estimated.5,9 Fibrin variables were assessed by technicians blinded to the origin of samples. Interassay and intra-assay coefficients of variation were <8%. For details see the online-only Data Supplement.
Continuous variables were presented as a mean and standard deviation or a median (interquartile range). Categorical variables were presented as numbers (percentages). The Kolmogorov–Smirnov test was used to test the normality of continuous variables. The χ2 test, Fisher exact test, Mann–Whitney U test, or Student t test were used as appropriate. Stepwise multiple logistic regression analysis was performed to determine the effect of clot variables on recurrences. Associations between the variables were expressed as odds ratios with 95% confidence intervals. The study was powered to have a 90% chance of detecting a 10% difference in clot lysis time using a P value of 0.01. To demonstrate such a difference or greater, ≥32 patients were required in each group. More details in the online-only Data Supplement.
The CVST and control groups did not differ regarding CVST risk factors, except severe thrombophilia, including deficiencies of antithrombin (n=1), protein C (n=1), protein S (n=3), and antiphospholipid syndrome (n=5), that occurred more often in the CVST group. Factor V Leiden was also more common among patients with CVST. Fibrinogen, D-dimer, and plasminogen activator inhibitor-1 antigen were similar in both groups, whereas tissue-type plasminogen activator antigen was slightly lower in the patients (Table 1).
The patients with CVST after anticoagulation withdrawal had lower Ks, higher D–Dmax, greater ΔAbs, and shorter lag phase, combined with hypofibrinolysis reflected by prolonged clot lysis time and lower D–Drate (Table 2). As expected, there was a strong inverse correlation of Ks with fibrinogen (r=−0.56, P<0.01 and r=−0.71, P<0.01 for the patient and control groups, respectively), but not with D-dimer. There was a negative correlation between Ks and D–Dmax (r=−0.38, P<0.01 and r=−0.49, P<0.01 for the patient and control groups, respectively). Lag phase and maximum absorbance of fibrin gels showed correlations with Ks (r=0.4, P<0.01 for patients and r=0.52, P<0.01 for the control group; r=−0.36, P=0.01 for patients and r=−0.67, P<0.01 for the control group, respectively). There were no associations among fibrin variables and risk factors, provoked/unprovoked event, time since the index event, or duration of anticoagulation (data not shown). At enrollment, 30 patients (60%) achieved complete recanalization, in 18 (36%) patients recanalization was partial, and 2 (4%) had no recanalization. There were no significant differences in fibrin variables between the patients with complete recanalization after anticoagulation compared with the remainder (Table I in the online-only Data Supplement).
Recurrence of CVST during follow-up (18–46; median, 36 months) was observed in 6 patients (12%; Table II in the online-only Data Supplement) and was associated with 21% higher fibrinogen, 20% lower Ks, and 17% greater D–Dmax measured at the time of anticoagulation withdrawal (Figure). No other recurrence-associated differences were noted (Tables II and III in the online-only Data Supplement). Multiple logistic regression adjusted for fibrinogen showed that the CVST recurrence is independently associated with elevated D–Dmax (>4.83 mg/L; odds ratio, 5.1; 95% confidence interval, 1.63–16.19; the upper quartile versus the lower quartiles).
This study is the first to demonstrate that faster formation of denser plasma fibrin clots displaying impaired lysability characterizes patients with CVST. Prothrombotic persistent changes observed after CVST were more pronounced compared with clot abnormalities reported in venous thromboembolism5 and ischemic stroke.6–8 They cannot be explained by fibrinogen concentrations and demographic/clinical factors. Higher prevalence of thrombophilia in CVST reported also in previous studies1,2 might, in part, contribute to abnormal clot characteristics.9 Importantly, denser clot structure expressed as D–Dmax may predict the recurrence of CVST, suggesting its prognostic value.
Our study has limitations. The size of the study groups was limited particularly in the subgroup analysis. The results of our study cannot be likely extrapolated to elderly patients with CVST because patients at the age of ≥60 years were excluded from this study. Similarly, we ruled out individuals with previous thromboembolic events that are known to be associated with prothrombotic clot phenotype.5,10 The small difference in the duration of the lag phase of turbidimetric curves measured in the patients with CVST and controls is negligible, although statistically significant. All the parameters were analyzed after thrombosis, which might per se alter clot phenotype.5 A common FXIII Val34Leu polymorphism which affects clot structure was not assessed.10
This study identifies a potential new risk factor for CVST and its recurrence. Our study indicates that in some patients with CVST permanent prothrombotic features of fibrin clots, regardless of thrombophilic factors, could contribute to the occurrence of this disorder and predispose to its recurrence. It might be speculated that prolonged anticoagulation may be considered for patients with abnormal clot characteristics. However, interventional studies are needed to validate this hypothesis.
Sources of Funding
This study was supported by a grant of the Polish National Science Centre (UMO-2013/09/B/NZ5/00254 to Dr Undas).
The online-only Data Supplement is available with this article at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.115.009528/-/DC1.
- Received March 24, 2015.
- Revision received May 26, 2015.
- Accepted June 12, 2015.
- © 2015 American Heart Association, Inc.
- Ferro JM,
- Canhão P,
- Stam J,
- Bousser MG,
- Barinagarrementeria F
- Martinelli I,
- Bucciarelli P,
- Passamonti SM,
- Battaglioli T,
- Previtali E,
- Mannucci PM.
- Undas A,
- Zawilska K,
- Ciesla-Dul M,
- Lehmann-Kopydłowska A,
- Skubiszak A,
- Ciepłuch K,
- et al
- Undas A,
- Podolec P,
- Zawilska K,
- Pieculewicz M,
- Jedliński I,
- Stępień E,
- et al
- Pera J,
- Undas A,
- Topor-Madry R,
- Jagiella J,
- Klimkowicz-Mrowiec A,
- Slowik A.
- Undas A,
- Ariëns RA.