Introduction
Thrombin is a key enzyme in hemostasis and thrombosis, regulating pro‐ and anticoagulant
reactions by interacting with other coagulation proteins and cellular receptors.1
Thrombin also carries out a plethora of biologically relevant actions that link to
other complex biological processes such as angiogenesis, inflammation, and cell proliferation.2
Thrombin is therefore likely to be involved in cancer, chronic inflammatory diseases,
atherosclerosis, and other diseases.
The capacity of blood to form thrombin is a critical determinant of hemostasis and
according to Hemker's first law, a low amount of thrombin produced in clotting blood
results in a bleeding risk, whereas high thrombin production translates into a risk
of venous thrombosis.3, 4, 5
In case of arterial thrombosis, we distinguish thrombosis related to atherosclerosis
(atherothrombosis) from arterial thromboembolism such as in atrial fibrillation. The
role of the coagulation system in the latter follows from the efficacy of oral anticoagulants
in preventing ischemic stroke. Here we want to focus on a less obvious question: What
is the relation between thrombin generation and clinical manifestations of atherothrombotic
disease?
The clinical manifestations of atherothrombosis evolve from ischemia and organ damage
downstream of the thrombus, notably in the heart (myocardial infarction), the brain
(ischemic stroke), and peripheral arteries (peripheral artery disease, PAD). That
thrombin plays a role here is strongly suggested by the observation that oral anticoagulation
as well as heparin have a preventive action on the reoccurrence of myocardial reinfarction,6,
7 all the more as the effect superimposes on that of aspirin8; nevertheless, the role
of thrombin remains rather equivocal. While straightforward risk associations between
thrombin generation and thrombosis have been published, also by us, several other
studies show inverse relationships (to be discussed below). The problem therefore
merits reconsideration.
Before reviewing the available evidence, it is necessary to stress the fundamental
difference between in vivo and in vitro thrombin generation.9 In vivo thrombin generation
(ie, the appearance of active thrombin inside the body) is to a limited degree a normal
phenomenon; markers of thrombin activity, such as prothrombin fragment 1.2, thrombin‐antithrombin
(TAT) complexes, and forms of degraded fibrin such as D‐dimers, are always detectable
in blood.
In vitro thrombin generation (TG) is a test that probes the capacity of blood (plasma)
to form thrombin. A completely normal person with a provoked thrombosis will show
signs of in vivo increased thrombin generation while their capacity to form thrombin
may be normal. A toddler with an antithrombin deficiency will have a high in vitro
TG but no signs (yet) of excessive thrombin production in their body.
Atherothrombosis
Atherothrombosis forms on the basis of atherosclerotic lesions in 1 or more large
arteries supplying the heart, brain, or other organs.10 Rupture or erosion of an atherosclerotic
lesion provokes a hemostatic reaction, which may occur repeatedly and which will not
cause major damage to the affected organ unless an occlusive thrombus forms11 that
stops blood supply downstream and thus may result in myocardial infarction (MI), or
ischemic stroke.
The plug forms through the interaction of platelets, plasmatic clotting factors, subendothelial
proteins, and atheromatous debris, exposed upon the wounded atherosclerotic lesion.
Platelets adhere to collagen and von Willebrand factor and the exposure of tissue
factor (TF) in the lesion activates the plasma coagulation mechanism.12, 13
A role of thrombin on the progression, persistence, and stability of atherothrombosis
is extremely likely (see above), but what is the precise role is an issue of long‐lasting
debate. Both Virchow and Rokitansky recognized the importance of both the fibrin‐forming
system and inflammation in atherosclerosis but they disagreed on the “primum movens,”
Virchow seeing inflammation as the first cause and Rokitansky clot formation (discussed
in 14, 15). Current insights suggest that they were both correct in that atherosclerosis
is to be recognized as a chronic inflammatory vascular disease in which coagulation
proteases are actively involved, to become instrumental in its ultimate consequence:
vascular occlusion due to the formation of thrombus.
In previous work and reviews, we and others have explored the molecular mechanisms
that may lie at the basis of the interactions between atherosclerosis and thrombin
formation.16, 17, 18 Mendelian randomization studies as well as case–control studies
show highly significant risk associations between different coagulation proteins and
atherosclerosis as well as atherothrombotic complications. The effect size is small,
however, and not always consistent.16 The clinical relevance of these associations
as well as the relevance of experimentally found causal effects remain under debate.
The interpretation of the beneficial effect of vitamin K antagonists is not necessarily
unequivocal because these drugs have multiple effects: in the first place on the coagulation
system itself, where they not only impair the function of procoagulant factors (II,
VII, IX, X) but also that of the delimiters of thrombin generation proteins C and
S.19 Furthermore, they inhibit vascular vitamin K‐dependent proteins such as Matrix
Gla protein and osteocalcin, which, in experimental animals, results in rapid calcification
of arteries. Recently the clinical analogue of this process has been recognized.20
Last but not least, pathology studies suggest that the use of warfarin is an independent
risk factor for plaque instability.21
In spite of all this, there is no evidence whatsoever that warfarin would actually
increase the risk of myocardial infarction (MI) or stroke, on the contrary. Likely
the effect of inhibition of thrombin generation outweighs the unfavorable effects
of vitamin K antagonists, at least when stable and therapeutic intensity anticoagulation
is achieved. This is corroborated by the observation that parenteral anticoagulation
(12.500 IU unfractionated heparin once daily) with heparin also protects against reinfarction.7
Different experimental studies show that application of the selective thrombin inhibitor
dabigatran markedly reduces atherogenesis in susceptible mice (apoE−/− background)
and beneficially affects the plaque phenotype.22, 23, 24, 25 Collectively, these studies
strongly suggest that there exists a link between atherosclerosis and atherothrombosis
on the one hand and thrombin on the other, a link that we thought timely to explore
from a clinical perspective.
Literature Studies
We have not performed a formal systematic review, but we have sought papers that focused
on in vivo thrombin generation via determination of fragment 1.2 or TAT complexes
and/or on in vitro thrombin‐generating capacity and their relation to atherothrombotic
disease. We used the search terms “thrombin generation” and (arterial or atherosclerosis
or thrombosis or atherothrombosis) in PubMed, updated until March 7, 2016. After manual
screening on title and subsequent on abstract, the search narrowed down to 57 papers
from a period starting in 1990. Although fibrinopeptide A and D‐dimer indirectly reflect
the presence of thrombin, we confined the search to direct measures of “thrombin activity”
or methods of thrombin generation so as to avoid data influenced by fibrin and the
fibrinolytic system.
Coronary Artery Disease
In vivo thrombin generation as judged by TAT, or F1.2 assay has been found to be increased
in symptomatic coronary artery disease (CAD),26, 27, 28, 29, 30, 31, 32, 33 lasting
for up to 2 years after the event,32, 34 as well as in patients with recurrent coronary
events.35 Some studies find it increased in unstable angina;36 however, Cooper et al
did not find significant associations between F1.2 and a first ischemic event.37 van
der Bom found no relation between TG markers and a history of CAD, although they observed
a significant increase of D‐dimer and a positive association between thrombin markers
and D‐dimer.38
An association between in vivo thrombin generation and severity of coronary vessel
disease on the angiogram29 or coronary calcification on the computed tomography scan39
has been reported. Granger et al found that baseline F1.2 was related to risk of death
or re‐infarction at 30 days following acute MI.31 Ardissino et al showed that both
high and low F1+2 levels were associated with cardiac death or re‐infarction in acute
coronary syndrome patients.40 Elevated TAT at baseline predicted death or re‐percutaneous
coronary intervention in ST‐segment elevation myocardial infarction patients, whereas
F1.2 only predicted events at 24 hours41; the data also tended to present a U‐shaped
relation between markers and major coronary events.
Several studies have shown a relation between age and sex and in vivo thrombin generation.
Of the cardiovascular risk factors, F1.2 was associated with fibrinogen for both sexes
and with factor VIIc in women in this population‐based study.42 TAT was associated
with Lp(a) in a subgroup of patients experiencing acute MI in the early morning as
compared to those with acute MI at other times.43
In summary, although it is evident from most studies that CAD is accompanied by thrombin
activity in vivo, there is no certainty on the precise relations between the clinical
picture and the extent of the phenomenon.
Ex vivo TG analysis was first reported in 2008, showing that it was faster, earlier,
and higher in its peak in subjects with a history of acute coronary syndrome as compared
to patients with stable CAD.44 Positive correlations were found between peak of TG
and fibrinogen, glucose, and C‐reactive protein, but only in those with stable CAD,
not in those with previous MI.44 Differences between the populations, for instance,
in the degree of hyperlipidemia, were suggested to be involved in some of these risk
associations. Indeed, Olivieri et al found that Apo C‐III was an independent risk
factor for CAD and that it was associated with endogenous thrombin potential (ETP)
and peak thrombin activity.45 This was not the case for total cholesterol, low‐density
lipoprotein, triglycerides, and apoE, suggesting that Apo C‐III may play a functional
role in thrombin generation.
In a study by Smid et al, there was a 7% higher ETP and a 15% higher peak thrombin
generation in acute MI patients than in controls. This could not be attributed to
a lower activity of the activated protein C (APC) system but rather to higher levels
of the procoagulant factors VIII and prothrombin.46 A more or less U‐shaped risk association
between ETP and CAD was observed by Borissoff et al39; the lowest levels in ETP were
found in those with mild CAD (115%) when severity was divided in quartiles based on
degree of luminal stenosis. Interestingly, only subjects with severe CAD had a significantly
increased ETP (average 130% of normal), whereas the increase in low‐grade and moderate
CAD did not reach statistical significance (averages 123% and 121%, respectively).39
Carcaillon et al did not find an association between history of CAD and increased
TG, but they did find an association with acute ischemic coronary disease and high
TG, more apparent in women than in men.47 While ETP and peak were elevated, the lag
time was slightly delayed in patients with a history of MI as compared to those without
such history; the inhibitory effect of thrombomodulin, indicative of APC resistance,
was not significantly different in these 2 subgroups. In those with symptomatic CAD,
a low ETP (+ high D‐dimer level) versus a high ETP (+ low D‐dimer level) was predictive
for recurrence (odds ratio 5.8 [95% CI 1.1–30.7]).46 In young women with MI, an increased
APC sensitivity was associated with risk (odds ratio 1.7); this apparent paradoxical
effect was attributed to negative effects of tissue factor pathway inhibitor and/or
protein S, but this remains speculative at this stage.48
A prolonged lag time and time to peak in patients with diabetes after acute coronary
syndrome were related to recurrent ischemic events at 6 months.49 In the LURIC study,
the event‐free survival in the quartile of individuals with the lowest ETP was much
lower than those with the highest ETP (P=0.004).50 In elderly subjects from the PROSPER
study (on the effects of pravastatin), only an increased normalized peak height was
significantly associated with incident coronary heart disease (hazard ratio 1.17 [95%
CI: 1.06–1.28], P=0.002).51 In the selected population of survivors from in‐stent
thrombosis, TG was significantly increased with reduced APC sensitivity, as compared
to those without recurrent stent thrombosis.52 In this study there was evidence of
increased contact activation as a contributing procoagulant factor.
In general, formation of thrombin and the potential to generate thrombin are altered
in patients with CAD. As seen for in vivo thrombin formed, also in vitro TG has a
tendency to be increased but the effects are not large and the precise patterns of
changes remain enigmatic. In fact it is not clear whether CAD and high TG have a common
cause (ie, atherosclerosis), or whether there is causal relationship between high
TG and developing atherothrombosis and/or its complications. In view of the important
role of platelets in thrombin generation and their well‐recognized involvement in arterial
thrombosis, it may be expected that studies on TG in platelet‐rich plasma (or whole
blood) may solve some of the abovementioned riddles.
Ischemic Stroke
In the studies considered for this review, it was not always clear whether ischemic
stroke was due to atherosclerosis, small‐vessel disease, a cardiac source, or another
cause,53 so we cannot provide any reliable information on the origin. In the early
1990s, oral anticoagulants were not yet routinely applied in patients with atrial
fibrillation, such that the absence of anticoagulation does not indicate that the
stroke was nonembolic. Taking these limitations into account, what do the available
studies on patients with ischemic stroke tell us?
In 1993 Yamazuki et al established that TAT levels were elevated in patients with
cardioembolic stroke versus patients with lacunar infarcts or controls.54 Fibrinopeptide
A was elevated in the acute and subacute phase of stroke, while only protein C antigen
was lower in the acute phase, possibly associated with consumption of this inhibitor.
Feinberg and colleagues tested coagulation activity in 1531 patients with atrial fibrillation
on aspirin and observed that F1.2 was associated with age, female sex, systolic blood
pressure, and heart failure but not with stroke.55 In those with cardioembolic stroke,
it appeared that F1.2 was minimally elevated (P=0.03). A subsequent study by Barber
et al showed that F1.2 and TAT were elevated in progressive stroke but only D‐dimer
and arterial blood pressure appeared to be independent predictors of stroke.56 Furie
et al did not find a correlation between the level of F1.2 and type of stroke.57 F1.2
was associated with large carotid artery plaques in stroke patients, not in controls,
and those with large plaques and high F1.2 levels were at greater risk of recurrent
stroke and death than those with larger plaques and lower F1.2 levels.58 These data
suggest that severity of atherosclerosis as well as its thrombogenic activity may
have an impact on the risk of recurrent thrombotic occlusions. Interestingly, F1.2
levels were associated with cognitive decline in a study by Stott et al, suggesting
that not only stroke itself but also its consequences may in part depend on thrombin‐mediated
processes.59 In summary, as in MI, there seems to be some association between in vivo
thrombin generation and ischemic stroke.
In vitro thrombin generation analysis was applied in an older study where Faber et al
found a significantly increased thrombin generation potential in the plasma of a subgroup
of young stroke patients.60 In more recent studies, after the clinical introduction
of semi‐automated methods, Carcaillon et al observed that ETP and peak height were
positively associated with risk of acute stroke (hazard ratio 1.16 and 1.31, respectively,
for 1 SD increase), more obvious in women.47 In contrast, Loeffen et al51 found a
highly statistically significant but inverse association between ETP as well as peak
height in a similar cohort study, albeit in older subjects than in the study by Carcaillon
et al.
In the acute phase of stroke, peak height was elevated both in cardioembolic and nonembolic
stroke subtypes61 and peak and ETP were elevated in early symptomatic versus asymptomatic
patients with carotid artery stenosis.
Among patients who had detectable microembolic signals, those with early symptoms
had a shorter “time to peak” than the asymptomatic ones, which suggests that thrombogenicity
enhances the symptoms caused by microemboli.62 This important study suggests that
the microemboli (or maybe smaller microvesicular material) from the diseased vessel
wall do more harm when present in a thrombogenic phenotype. In this context, studies
that show a link between intima‐media thickness, markers of thrombin (F1.2), and risk
of stroke are also of importance.63, 64
In general, hypercoagulability, as witnessed by thrombin formation in vitro or in vivo,
is likely to be one of the factors that link carotid artery plaque lesions to recurrent
vascular complications (ischemic stroke). Risk associations between TG and microembolic
signals as well as cognitive decline deserve more study in order to better appreciate
these potentially important interactions.
Systemic Atherosclerosis in Peripheral Artery Disease (PAD)
Two studies published in 1993 addressed markers of thrombin in patients with PAD,
showing a positive association between TAT and PAD65 and elevations of both F1.2 and
TAT in patients with PAD, however, not related to severity of atherosclerosis.66 Heinrich
et al and van der Bom and colleagues did not find significant associations of F1.2,67
or F1.2 or TAT38 with prevalent PAD, respectively. One published report shows that
thrombin generation had a negative association with patients that reached an atherosclerotic
clinical end point (low ETP and future thrombotic event, odds ratio 11.7). These authors
suggested that consumption of coagulation proteins in more severely affected patients
could explain the negative risk association seen for thrombin generation,68 but evidence
supporting this assumption is lacking.
Biochemical Mechanisms Linking Thrombin to Atherothrombosis
Thrombin is the pivotal enzyme of hemostasis. It originates in a complicated network
of reactions, full of checks and balances and once formed it displays a plethora of
actions primarily leading to hemostasis and wound repair but with important interactions
with inflammation and cell proliferation. Recent research from, for example, the Furie
group has clearly shown that thrombin plays a role in the earliest phases of hemostasis.
Within 12 s after a lesion has been made, fibrin can be seen, so that thrombin must
have appeared even earlier.69, 70 This challenges the old dogma of primary and secondary
hemostasis and makes us believe that it is not bizarre that thrombin plays a role
in arterial thrombosis and primary plug formation. The same work shows, however, that
a role is played by numerous other elements, notably platelet‐ and microparticle‐related
but also from endothelial‐ and subendothelial tissues. It may therefore not be expected
that the capacity of the plasma to form thrombin is the only parameter that governs
the process.
Among the multiple functions of thrombin, there are those that are immediately related
to further thrombin production, such as activation of factors V, VIII, and XI. In
addition, thrombin activates platelets through protease activated receptor (PAR) receptors
and this provides critical input of activated platelets as a source of phospholipids
to drive coagulation reactions, as well as release of additional procoagulant proteins
(eg, factor V) and enzymes. Even fibrin, the main thrombin product, by activating
platelets via von Willebrand factor, fosters further thrombin formation.71, 72
Although the net effect of thrombin is prothrombotic, we should not forget that it
has antithrombotic actions as well. An intriguing anticoagulant action of thrombin
is the activation of protein C, via binding of thrombin to thrombomodulin at cell
surfaces (endothelial cells and others). Theoretically, given the density of receptors,
the microvascular bed is an important reservoir of functional thrombomodulin and it
may also be the most potent source of APC generation to control local but also systemic
pro‐inflammatory (and procoagulant) forces. APC can subsequently act on PAR‐1 in concert
with endothelial protein C receptor, to protect the vasculature against inflammatory
stimuli. Thrombin also acts on PAR‐1 to mediate more offensive actions, and the regulation
of this delicate balance has been studied in detail over the past decades.73 As a
further example of an anticoagulant action of thrombin, we mention that the presence
of minute amounts of thrombin, too low to make plasma clot, can lead to the formation
of free factor Va (ie, not lipid bound), which is a potent inhibitor of the VII‐TF
complex.74
This regulated cellular network of pro‐ and anticoagulant thrombin‐driven actions
makes it imaginable that both low and high thrombin concentrations can be relevant
in the pathophysiology of arterial vascular disease and atherothrombosis. Low amounts
of thrombin would theoretically provide insufficient drive for PC activation, to protect
against inflammation. Relatively high thrombin concentrations could overcome locally
protective effects of APC to drive PAR‐mediated cell signaling functions.
Intriguingly, the presumed cellular actions of thrombin assume that sufficient free
thrombin is available in plasma. The coagulation mechanism is a potent force driving
fibrin formation when needed (ie, in situations of bleeding when, locally, high concentrations
of thrombin and fibrin are required). Systemically, any excess free thrombin will
be rapidly quenched by AT and other inhibitors. Nevertheless, the reaction with AT
takes place in free solution, so there must be a finite concentration of free thrombin
in the plasma. On basis of the half‐life time of the TAT complex and the reaction
constant of its formation and the plasma concentration of AT, it can be calculated
that, in order to maintain a given concentration of TAT, 0.025 times that concentration
of free thrombin must be present in plasma. If this concentration is available for
AT, it is also available for thrombomodulin and for making anticoagulant free factor
Va (see above; 73). In real life, the situation will be more complicated than just
chemical reactions because flow and diffusion will play their roles; nonetheless,
there is no interaction of thrombin with any ligand without free thrombin. In the
context of atherogenesis and atherosclerosis, TG is linked to early atherosclerosis,
likely one of the drivers of this complex process.75 This model is strongly supported
by experimental studies.22, 23, 24, 25
It should also be kept in mind that there is a form of thrombin, meizothrombin, that
is enzymatically active but that remains bound to phospholipid surfaces and therefore
can be carried by lipid membranes, on microvesicles or otherwise and in this form
“escape” inhibitors. A second thrombin “protection” mechanism may simply be related
to the localization of thrombin formation; when accelerated TG and fibrin formation
are induced, such as at sites of bleeding or plaque rupture, the process of TG takes
places in situ and the concentration at phospholipid surfaces may facilitate TG to
proceed in a way where inhibitors such as AT do not easily get access. This protection
has been reported a long time ago for the tenase and prothrombinase complexes (reviewed
in 76), but perhaps most of the formed thrombin also stays locally active. The reason
that thrombin may not be scavenged immediately may be that atherothrombosis is a process
that takes place in the context of a damaged atherosclerotic lesion, in which besides
proteins many cells and microvesicles provide a tight cell–fibrin network that does
not allow much free protein transfer in the first instance.
A third mechanism mediating TG reactions involves lipid components. The idea of connections
between lipids and coagulation goes back to the work by Meade and colleagues showing
elevated factor VII clotting levels in patients with CAD.77 In particular, effects
of a high‐fat diet on lipids and coagulation activity have since been explored, showing
increased factor VII postprandial activity, linked to total fat intake rather than
triglycerides (summarized in 78). Whether or not the effects on factor VII activity
accelerate TG remains questionable, also since factor VII does not emerge as an important
determinant of TG in subsequent studies. From the present analysis, Apo‐CIII and Lp(a)
emerge as determinants of TG. Olivieri et al provide an explanation for the effect
of Apo‐CIII showing that elevated concentrations of Apo CIII are associated with an
increase in thrombin activity to an extent comparable to the carriership of G20210A
gene variant and modulating TG in subjects with or without CAD.45 Direct effects of
Lp(a) on TG have not been reported. However, Lp(a) is an independent risk factor for
cardiovascular disease and is probably involved in many steps of atherogenesis. The
pleiotropy of this lipoprotein extends its influence toward several serine proteases
causing disturbances in blood coagulation.79 The best known are probably linked to
inhibition of fibrinolysis. Other lipid‐related effects on TG may be mediated by high‐density
lipoprotein particles, which stimulate anticoagulant effects of APC and protein S.80
Finally, phospholipid transfer protein transfers lipids between donors and acceptors
(eg, from high‐density lipoprotein to very low‐density lipoprotein) and provides an
anticoagulant action in plasma, by inhibiting generation of factor XIIa in the presence
of very low‐density lipoprotein.81
All these mechanisms acting together are certainly complex enough to form a “nonlinear
system” (ie, a system in which, on a theoretical basis, it can be assumed that the
relation between 1 concentration and the other of whatever pair of reactants may show
jumps and irregularities that are dependent upon a third reactant in a manner that
is not easy to predict). Notably, it is not surprising that the actions of thrombin
can switch from protective (generating APC) toward more offensive functions that act
in a prothrombotic and pro‐atherogenic manner.
Finally, recent work suggests that the contact system (factor XII, bradykinin, and
prekallikrein) may be a more important determinant of atherothrombosis than previously
thought.82 Several in vivo studies support the concept that the contact system, either
directly or through factor XI‐mediated thrombin generation, boosts fibrin formation
and the formation of a tight fibrin clot.83, 84, 85 On the other hand, factor XIIa
also drives part of the fibrinolytic pathway. The current development of specific
inhibitors against factors XIIa, Xia, and maybe other contact proteins may help to
unravel the role of these molecules in the near future.
Conclusions and Suggested Avenues for Research
In contrast to studies in venous thromboembolism, where the author's (Hemker) concept
of “more thrombin is greater thrombosis risk” is readily confirmed (summarized in
86), the precise role of thrombin in atherothrombosis—though undoubtedly present—is
hard to derive from clinical data. In the settings of arterial thrombosis, several
issues must be considered. We tried to cope with the heterogeneity of the process
by focusing on atherothrombosis. However, atherothrombosis also occurs in different
vascular beds, and the differences in organ‐related effects may be substantial. Some
of the studies on stroke we reviewed include patients with cardioembolic stroke, clearly
a distinct entity, also in terms of risk factors.
While the role of platelets and other cellular elements in atherogenesis and thrombosis
goes undisputed, a role of coagulation proteins and in particular thrombin has long
been doubted but is evident from the clinical and experimental body of evidence that
we reviewed. However, for a better understanding of the precise mechanisms by which
thrombin displays its many functions, further clinical and experimental studies will
be necessary. Automated in vitro thrombin generation is a relatively new technique
that can be expected to yield more information in the years to come. Thrombin generation
in platelet‐rich plasma—a very useful technique for the study of the interplay between
platelets and clotting factors87—has not as yet been clinically explored to any significant
extent. This seems pertinent now that millions of patients are being exposed to direct
oral thrombin (formation) inhibitors (non–vitamin K oral anticoagulants)! The association
between thrombin and atherothrombosis risk does not show a linear relationship, and
this aspect alone makes it quite important to carefully observe what we are actually
achieving with long‐term inhibition of thrombin in vivo. Is this inhibitory effect
similar for men and women, is it age dependent, dependent on cardiovascular disease
risk factors, on lipid profiles, etc? Short‐ and medium‐term follow‐up did not reveal
any unexpected side effects of non–vitamin K oral anticoagulants, but vascular effects
may take a decade or so to be detected (see the history of warfarin‐associated calcification).
Given the limited knowledge of all biochemical interactions that thrombin may be engaged
in, building a strong knowledge base on thrombin and cardiovascular disease seems
of eminent importance.
Disclosures
ten Cate and Hemker are consultants to Diagnostica Stago. ten Cate received fees for
lectures and ad hoc consultations from various diagnostic and pharmaceutical industries
and is Chair of the board of the Dutch Federation of Anticoagulation clinics. He is
a Fellow of the Gutenberg Research Foundation, Center for Thrombosis and Haemostasis,
Gutenberg University, Mainz, Germany.