The role of tissue factor pathway inhibitor in the development and progression of ischemic cerebral lesions due to cerebral micro-angiopathy

In the Netherlands annually 30.000 individuals suffer from a stroke. A fifth of
these are lacunar type 3. Lacunar infarcts are small infarcts (2-20mm in
diameter) in de deep cerebral white matter, basal ganglia, or pons, and result
from the occlusion of a single small perforating artery supplying the
subcortical areas of the brain4. At autopsy, Fisher5 distinguished two types of
underlying vascular pathology in patients with lacunar infarcts;
lipohyalinosis/arteriolosclerosis and micro-atheromatosis. Even during life,
these two types can be distinguished. Patients with a single lacunar infarct,
more often have atheromatosis, and patients with concomitant white matter
lesions and asymptomatic lacunar infarcts more often have lipohyalinosis or
arteriolosclerosis6. More recently, we found that patients with the second
subtype have a more unfavorable prognosis7. On the basis of these findings we
hypothesized that different entities with different underlying
pathofysiological mechanisms exist.
In 2003 we started a prospective follow-up study of patients with a first ever
lacunar stroke syndrome with compatible lesion on MR-scanning of the brain (MEC
04-001). By the modified Fazekas scale2, the concomitant white matter lesions
(WMH) and asymptomatic lacunar infarcts were scored. After at least 3 months, a
single fasted blood withdrawal was performed , and plasma was stored. D-dimer,
Von Willebrand factor (vWF)-antigen, soluble Thrombomodulin (sTM) and tissue
factor pathway inhibitor (TFPI) were measured using ELISA or
immuno-turbidimetric assay. Chi square analysis was used to relate
concentration of plasma markers (divided into tertiles) to severity of white
matter lesions (divided into a dichotome variable). In this pilot study we
found, high levels of TFPI to be associated with extended WMH (p=0.026). The
distribution of sTM and vWF was equal between the two groups. There was no
indication of influence of activated coagulation, since D-dimer levels were not
associated with severity of disease. We concluded that higher levels of TFPI in
lacunar stroke patients with extensive WML could suggest endothelial
dysfunction, the lack of difference in plasma levels of vWF and sTM makes this
hypothesis unlikely. In the absence of activated clotting as a significant risk
factor, the specific contribution of TFPI in the pathogenesis of lacunar stroke
is unclear.
TFPI is the main inhibitor of the factor VIIa (FVIIa)/Tissue Factor (TF)
pathway of coagulation (extrinsic pathway). TFPI first binds and inhibits
factor Xa, followed by binding of TF and FVIIa, leading to an inactive
quaternary complex. About 75% of all TFPI is bound, by a positively charged
carboxy-terminus, to negatively charged glycosaminoglycans on the luminal
surface of the endothelium. By injection of heparin this pool can be released
into the circulation8.In most studies only lipoprotein-bound and free TFPI is
evaluated, but this only constitutes about 22,5% of the total amount of TFPI.
Ariens et al. found normal levels of TFPI before administration of heparin, but
abnormal low levels of TFPI after injection of heparin in young patients with
venous and arterial thrombosis 9. On the other hand, Leurs et al. found in
patients with diabetes mellitus with albuminuria- as a manifestation of
generalized angiopathy - high levels of TFPI, compared to patient with DM
without albuminuria. After administration of heparin, the increase of TFPI
-release was also higher in the group of patients with albuminuria. The authors
suggest that this could be the result of altered endothelial glycoaminoglycans.
So, in this study, as in our data, high levels of TFPI are an expression of the
activated endothelium and not of changes in coagulation, as levels of D-dimer
were normal.

Primary Objective:
1)Is the release of TFPI by endothelium after admission of heparin different
between lacunar stroke patient and healthy controls?
2) Is the release of TFPI by endothelium after admission of heparin different
between lacunar stroke patients with or without concomitant ischemic white
matter lesions?
Secondary Objective(s): Not applicable

The study is an non-randomized open intervention study, consisting of an single
IV dose of heparin. The infusion of heparin is preceded and followed by blood
withdrawal from an antecubital vein.

Single dose of heparin 7500 IU (intravenous)

Two blood withdrawals, before and after IV administration of a single dose
Heparin (7500 IE). Risks associated with the intervention: hematoma puncture
site and haemorrhage elsewhere. We want to investigate if endothelial
dysfunction in plausible in lacunar stroke.