ORIGINAL ARTICLE
Deep Venous Thrombosis in Stroke Patients during
Rehabilitation Phase
Yukihiro Hara

The Department of Rehabilitation Medicine, Nippon Medical School,
Chiba Hokusoh Hospital, Chiba, Japan(Received for publication on January 8, 2008)(Revised for publication on April 28, 2008)(Accepted for publication on May 15, 2008)

Abstract. Purpose: The purpose of this study was to examine the incidence, factors, and effects of antiplatelet and anticoagulant agents on sub-acute and chronic ischemic stroke patients during the rehabilitation phase for rates of deep venous thrombosis (DVT) from theperspective for rehabilitation medicine.
Methods: In this study of 272 patients undergoing rehabilitation for completed cerebral infarction, multiple circumference measurements of calf and thigh along with presence or absence of symptoms (congestion, swelling, skin redness, warmth, pain, pigmentation, fever
and/or Homan sign or Luck’s sign) documented in the physical examination were recordedin all patients. Patients with these symptoms suggestive of DVT were included for D-dimer
assay and venous duplex ultrasonography to confirm presence of DVT.
Results: DVT was documented in 24 patients (8.8%), most of whom displayed distal DVT
on the hemiparetic side. A significant association was seen between occurrence of DVT and
more severe lower limb paresis, manifesting as gait disturbance, severe calf muscle spasticity, use of ankle-foot orthosis (AFO). A significant increase in development of DVT was associated with severe spasticity in hemiparetic calf muscles (odds ratio (OR) 28.2; 95% confidence interval (CI), 6.9-113.5). Cilostazol seemed to be the only effective antiplatelet drugfor preventing DVT in cerebral infarction patients.
Conclusion: Incidence of DVT in the rehabilitation phase following stroke was not low,which was predominant as distal DVT on the hemiparetic side. Lower limb paresis, gait disturbance, calf muscle spasticity and use of AFO contributed to occurrence of DVT. It is likely that micro-injuries in the venous endothelium due to spasticity and AFO might cause
DVT. Cilostazol seems effective for protecting against venous endothelial damage following
DVT. (Keio J Med 57 (4) : 196－204, December 2008)
Key words: stroke, hemiparesis, deep venous thrombosis, antiplatelet drug

Introduction
Deep venous thrombosis (DVT) is a common complication in patients with acute thromboembolic stroke.1,2
Incidence of DVT during the first 2 weeks after stroke
has been reported at between 27% and 75% among untreated control patients in several randomized prophylaxis trials.3 The incidence and clinical impact of DVT
during the chronic rehabilitation phase following stroke
are, however, less well appreciated. DVT is difficult todiagnose in rehabilitation patients, as the clinical signs
and symptoms of this condition are nonspecific. Most
cases are identified by Doppler ultrasonography, plethysmography or contrast venography, all of which are expensive and relatively time-consuming techniques. Recent studies have suggested that the latex D-dimer assay
can be used to exclude DVT and pulmonary embolism(PE) more quickly and in a less costly manner than othermethods.4 Few reports have examined DVT during thechronic stroke rehabilitation phase and some studies

Correspondence author: Yukihiro Hara, MD, Ph.D. Nippon Medical School, Chiba Hokusoh Hospital, Department of Rehabilitation Medicine, 1715 Kamakari, In-bamura, Inbagun, Chiba Prefecture, Japan 270-1694, Tel: (Business) +81-476-99-1111, (Home) +81-42-333-4105, Fax: +81-476-99-1917, E-mail:hara-y@nms.ac.jp
196Keio J Med 2008; 57 (4):196－204

have demonstrated that the prevalence of DVT is alsohigh in patients with stroke who develop swelling of thehemiparetic limb during rehabilitation. 5,6 In anotherstudy of 102 consecutive patients undergoing rehabilitation for completed stroke, incidence of DVT was 11% ata mean of 60 days after stroke onset (median, 49 days;
range, 14-138 days), with a 2% incidence of fatal pulmonary embolism.7 A recent study detected lower extremity
DVT in 34% of patients, and 23% of patients displayed
isolated calf vein thrombosis among patients admitted to
inpatient rehabilitation programs.8 Several previous studies have suggested that DVT is less frequent among
Asians than among Caucasians.9 De Silva et al.,10 however, reported that DVT following ischemic stroke
among Asians is common and associated with poor functional outcome. As for medical factors associated with
DVT in the rehabilitation phase, a history of cardiac arrhythmia appears to be associated with lower risk of
DVT, while myocardial infarction, congestive heart failure, hypertension, diabetes mellitus, chronic heart failure
and anemia are not significantly associated with risk of
DVT.11 Understanding the incidence and characteristics
of DVT complicating chronic ischemic stroke is important, since the benefit of anticoagulation for prophylaxis
or treatment of venous thromboembolism must be
weighed against the risk of possible secondary hemorrhagic conversion of cerebral infarction and major hemorrhage. Aspirin should be routinely used soon after cerebral infarction, but its role as an adjunctive method toprevent DVT is unclear.
The present report examined the incidence, factors andeffects of antiplatelet and anticoagulant agents on subacute or chronic ischemic stroke during the rehabilitation
phase for rates of DVT from the perspective of rehabilitation medicine.
Methods
Patient Population
A total of 296 stroke rehabilitation patients admitted
consecutively to freestanding rehabilitation hospitals between September 2005 and August 2007 were eligible
for this study. The study included patients ≥18 years old
who had suffered a stroke, whose primary reason for rehabilitation was disability resulting from stroke, and who
were rehabilitation inpatients or outpatients for ≥3 days.
Stroke, defined as an acute event of cerebrovascular origin, causing focal or global dysfunction lasting >24hours, was confirmed by both clinical and radiographic
evaluation. All patients admitted to university hospitals
or rehabilitation hospitals after completed stroke were
followed from admission to discharge and at the outpatient clinic for >2 months. Subjects were medically stable and able to participate in an active rehabilitation pro-197

gram. Inclusion criteria included: 1) ischemic stroke (diagnosed by a consultant neurologist based on clinicalpresentation and computed tomography (CT) or magnetic resonance imaging of the brain performed within 48
hours of symptom onset); and 2) Stroke Impairment Assessment Set (SIAS)12 <5; for the lower limb affected bystroke at time of screening study. Exclusionary criteria
were: 1) hemorrhagic stroke; 2) >50 weeks post-stroke;3) active cancer; and 4) past history of DVT or PE. Medical histories were obtained on all patients through a review of medical records from the referring hospital andverification against medical assessment at rehabilitation
centers. Physicians assessed the date of screening examinations, severity of weakness and level of mobility for
all stroke patients on day of admission to the rehabilitation centers. The reviewers also identified use of antiplatelet agents and anticoagulants that were prescribedon transfer to rehabilitation center. All patient data werecollected in accordance with the Declaration of Helsinkiof 1975, as revised in 1983, and study protocols were approved by the local institutional review board.
Patient histories were reviewed to ascertain results ofclinical examinations and Doppler studies. Multiple circumference measurements of the calf and thigh as alongwith presence or absence of symptoms (congestion,swelling, skin redness, warmth, pain, pigmentation, fever
and/or Homan sign or Luck’s sign) documented in thechart on the day of physical examination were recordedin all patients. Asymmetries in calf and thigh measurements were documented as an important clinical sign of
DVT in patients in whom asymmetry exceeded 2.5 cm,13
as the difference in calf diameter is reportedly useful for
ruling in DVT, while absence of calf swelling or difference in calf diameter is useful for ruling out DVT.14 Patients with these symptoms suggestive of DVT occurring
at any time during rehabilitation were considered for inclusion in the study for D-dimer assay. The D-dimer assay is a reliable method for ruling out DVT. In the rehabilitation setting, this assay can be used as a routine
screening test or to assess cases of suspected DVT. Venous duplex ultrasonography was used as a criterion
measure to confirm presence of DVT, as these procedures are recommended as the “first-line” diagnostic instrument in evaluation of DVT.15,16,17 Doppler ultrasonography studies were performed using a Phillips Advanced Technology Laboratory 5000 device with a
7.5-MHz linear probe. B-mode two-dimensional imaging
was used to visualize and identify where the common
femoral superficial and popliteal veins divide into multiple calf veins (calf trifurcation) of the lower extremity.
Light probe compression, milking method and color flow
analysis were used to investigate DVT. The supporting
criterion for DVT was continuous low flow with decreased or no augmentation (using calf squeeze) on Doppler spectral analysis, and partial or complete vessel wall

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Hara Y: DVT in Stroke Patients during Rehabilitation

Table 1

DVT (+)Meanage(y)
68.0

M16, F8

DVT (-)

69.2

M162, F86 188(75.8) 26(10.5) 34(13.7)(n=24)(n=248)sex, nstroke type, n(%)
(T)
(L)
(E)
18(75)
2(8.3)
4(16.7)

Median SIAS
(hip) (knee) (ankle)
3
3
1
3

3

Median MAS

Median gait FIM

2

4

1

4

2

DVT: Deep venous thrombosis, T: atherothrombotic infarction, L: lacuna infarction, E: cardiogenic embolism, SIAS: Stroke
Impairment Assessment Set, MAS: Modified Ashworth scale, FIM: Functional Independent Measurecompression failure.18 Lack of vein compressibility was
the sole diagnostic criterion for diagnosis of DVT. 19
Thrombi identified in the common, deep and superficial
femoral veins, as well as those found in the poplitealvein, were classified as proximal DVTs. Calf DVTs included those involving the tibial, peroneal, soleal, gastrocnemius, and perforator veins. Thrombosis below the
popliteal vein was categorized as distal DVT.
SIAS score12 was assessed for the paretic lower limb
by certified trial coordinators. If both lower limbs wereparetic, SIAS score of the weaker limb was recorded.
Foot and leg function were staged according to SIAS.
Ultrasonography studies and SIAS scoring were performed for patients in hospital, with those discharged returning as outpatients. Patients were classified according
to Functional Independent Measure (FIM) gait categories. Gait category of FIM was utilized to assess thefunctional status of patients at physical examination.
These assessments were performed by a single trained
trial coordinator who was blinded to patient demographics, stroke subtype, stroke severity and Doppler results.
The Modified Ashworth Scale (MAS)20 was scored as aclinical measure of spasticity during sitting, with thehemiparetic side calf muscles in an extended knee position.
Statistical analysis
All analyses were performed using Microsoft Office
Excel 2007 and Excel statistical software (SSRI, Tokyo).
The χ2 test and Mann-Whitney U test were applied forstatistical analyses. Statistical significance was set at alevel of p<0.05. Multiple logistic regressions were performed using Excel statistical software with clinical features as independent variables, and the presence or absence of DVT as the dependent variable. Variables studied were: age; gender; SIAS score (grade 0 to 5); MAS(grade 0 to 4); gait FIM (grade 1 to 7); and previous
treatment with aspirin, ticlopidine, cilostazol or warfarin.
An alpha level of 0.05 was considered significant.
Results
Twenty-four patients were excluded from analysis be-

Fig. 1 Patients flow chartcause of exclusion criteria. Data from 272 patients werethus included in the analysis. Physical examination was
performed at a mean of 89.5 days (median, 98 days;
range, 32-345 days) after stroke onset. Table 1 showsbaseline characteristics of the 272 eligible patients (demographics, stroke type, lower limb paresis, spasticity
and gait ability with and without DVT). All patients wereon antiplatelet or anticoagulant therapy unless contra-indicated. To assess the consistency with which medications prescribed on transfer to rehabilitation were continued unchanged during the rehabilitation hospital stay andoutpatient clinic. A total of 54 patients were symptomatic
and/or had D-dimer >0.5 μg on examination for DVT at
the time of Doppler scans among the 272 patients; initially eligible. Asymmetry in calf and/or thigh measurements was a particularly important clinical sign. DVT
was documented in 24 patients (8.8%) undergoing rehabilitation. Twenty-one distal and 3 proximal DVT of thepatients who underwent Doppler study were found on

Keio J Med 2008; 57 (4):196－204

199

Fig. 2 Lower extremity hemiparesis (distal SIAS) and DVT. A significant association existed between occurrence of DVT and more
severe lower limb paresis as measured by SIAS score (p<0.05: Mann-Whitney U-test).

the hemiparetic side (Fig. 1). Bilateral DVT was present
in 3 of these patients. DVT was diagnosed at a mean of
233 days (median, 222 days; range, 66-345 days) after
stroke onset.
Patients who had DVT did not differ significantly fromthose without DVT in terms of age or sex. No association was seen between occurrence of DVT with infarction type and presence of large stroke. Median SIAS oflower extremity SIAS of lower extremity hemiparesis
was 3 (hip), 3 (knee), 1 (ankle) for patients with DVT
and 3 (hip), 3 (knee), 2 (ankle) for patients without DVT.
Ninety-four percent of the patients in whom asymmetry
in calf and/or thigh measurements exceeded 2.5 cm werediagnosed as having DVT according to Doppler study. A
significant association was seen between occurrence of
DVT and more severe ankle joint paresis as measured by
SIAS ankle score (p<0.05, Mann-Whitney U test) (Fig.
2). There was no significant association between DVTand SIAS hip or knee scores. Median FIM gait was 4 forboth patients with and without DVT. However, FIM gait
score was significantly lower for patients with DVT thanfor patients without DVT (p<0.05, Mann-Whitney Utest) (Fig. 3). Median MAS of calf muscles was 2 for patients with DVT and 1 for patients without DVT. Ankle
MAS score was significantly higher for patients with
DVT than for patients without DVT (p<0.001, MannWhitney U test) (Fig. 4). A significantly higher proportion of patients with DVT used klenzac or plastic anklefoot orthosis (AFO), when compared with patients with-out DVT (p<0.05, χ2 test) (Fig. 5). DVT was seen in 17
patients with aspirin, 7 patients with ticlopidine and 2
patients with warfarin. No patient with cilostazol suffered DVT in this study (Fig. 6).
Multiple logistic regression analysis using age, sex,
stroke type, SIAS (hip, knee and ankle), MAS, gait FIM
score, need for orthosis, antiplatelet drugs and anticoagulant drug as variables showed only spasticity (MAS) andcilostazol as independently associated with presence of
DVT. A significant increase in development of DVT was
associated with severe spasticity in hemiparetic calfmuscles (odds ratio (OR) 28.2; 95% confidence interval(CI), 6.9-113.5). No significant increase in DVT was associated with age (OR 1.046; 95% CI, 0.981-1.116), sex(OR 1.461; 95% CI, 0.335-6.387), stroke type (OR1.709; 95% CI, 0.463-6.306), SIAS hip (OR 1.286; 95%
CI, 0.077-21.539), SIAS knee (OR 2.630; 95% CI,
0.158-43.891), SIAS ankle (OR 0.630; 95% CI,
0.239-1.660), gait FIM score (OR 2.197; 95% CI,
0.774-6.236) or use of AFO (OR 0.878; 95% CI,
0.313-2.465). Only use of cilostazol (OR <0.001; 95%
CI, <0.001 to >999.9) showed a significant protective effect against VTE risk. Neither warfarin (OR 0.686; 95%
CI, 0.054-8.779) nor any other antiplatelet agents (aspirin (OR 4.892; 95% CI, 0.382-62.716), ticlopidine (OR3.469; 95% CI, 0.235-51.208)) reached statistical significance in multiple logistic regression analysis.
Three patients were on heparin infusion after diagnosis
of proximal DVT. One individual with proximal DVT

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Hara Y: DVT in Stroke Patients during Rehabilitation

Fig. 3 Gait FIM and DVT. FIM gait score was significantly lower for patients with DVT than for patients without DVT (p<0.05:
Mann-Whitney U test).

Fig. 4 Calf muscles spasticity (MAS) and DVT. Ankle joint MAS was significantly higher for patients with DVT than for patients
without DVT (p<0.001, Mann-Whitney U test).

displayed symptomatic PE, confirmed on spiral CT ofthe thorax, which was treated with anticoagulation andoxygen supplementation and resolved completely. One
patient, who had a filter in place for treatment of earlyvenous thromboembolism, developed recurrent venous
thromboembolism during rehabilitation.

Discussion
Patients undergoing in- or outpatient rehabilitation are
at increased risk for DVT, but accurate diagnosis of DVT
by clinical examination is reportedly complicated andfrequently unreliable. In contrast, recent attempts to de-Keio J Med 2008; 57 (4):196－204

201

Fig. 5 Orthosis and DVT. A significantly higher proportion of patients with DVT used AFO, when compared with patients without
DVT (p<0.05, χ2test).

Fig. 6 Antiplatelet, anticoagulant drugs and DVT. (Asp, Aspirin;
TP, Ticlopidine; CZ, Cilostazol; Wa, Warfarin) Numbers inside
the graph show the number of subjects with DVT among subjects
receiving each drug.

lineate clinical signs of DVT have proven more successful. A recent study found swelling, immobility and fever
to be associated with DVT confirmed by venography.
Sioson6 reported that profound weakness, male gender,interval between stroke onset and DVT examination,
edema and hyperpigmentation were independently associated with positive DVT in patients admitted to a rehabilitation hospital. Diamond13 demonstrated the abilityof certain subspecialists to diagnose DVT by clinical examination. Specificity of clinical diagnosis is low, as thesymptoms and signs can all be caused by nonthrombotic
disorders. Nevertheless, clinical findings are an important, if not crucial, adjunct to objective diagnostic testing. Since pretest probability plays a pivotal role in test
selection and interpretation, a well-recorded history andcareful physical examination are crucial parts of the diagnostic pathway. It should be kept in mind as a screening test that difference of calf diameter is an important
sign for ruling in DVT among clinical signs, while absence of calf swelling or a difference in calf diameter isuseful for ruling out DVT.14 Individual clinical features
are of limited value in diagnosing DVT and overall assessment of clinical signs is useful for diagnosis of DVT
as a screening test.14 Therefore, we adopted overall assessment of clinical signs as a screening test at first.
These clinical features often increased gait disturbanceof stroke patients in this study. As a noninvasive methodfor diagnosis of DVT, venous ultrasonography (compression ultrasonography with or without Doppler flow assessment) has been extensively evaluated and widelyused. In symptomatic patients with suspected first episode of DVT, clinical assessment and D-dimer testing
are complementary to testing with venous ultrasonography and impedance plethysmography.21
Most DVT patients displayed distal type in this study.
Among the crural veins, the soleal vein is particularly
important as an initial site of DVT. The detection rate of202

Hara Y: DVT in Stroke Patients during Rehabilitation

Fig. 7 Venous flow pattern with muscle contraction of gastrocnemius and soleal vein28
PTv: posterior tibial vein, Pev: Peronal vein. In gastrocnemius muscle the venous blood return flows from distal to proximal portion
with muscle contraction as the muscle pomp. On the other hand, in soleal muscle the venous blood flows to various directions withmuscle contraction because of the mesh-like venous structure and soleal muscle hyper tone might induce the stagnation of venous flow.

thrombi in the soleal vein has been reported to be highest, at 90%.22 Management of calf vein DVT has also
been controversial. While it is well established that calfvein DVT rarely causes pulmonary embolism, some argue that the propensity to propagate into proximal veinsand become both symptomatic and a potential source ofembolus warrants formal anticoagulation.7 Distal (calf)
DVT poses a low risk for embolization, in contrast to thehigh risk with proximal (thigh) thrombi.23 Proximal venous thrombosis requires antithrombotic therapy. With
deep venous thrombosis confined to the calf, serial noninvasive testing is safe to perform, with antithrombotic
therapy used only for patients in whom thrombus subsequently extends into the thigh. Whether therapeutic anticoagulation is superior to heparin prophylaxis in the prevention of DVT has been impossible to determine. Useof warfarin at a fixed low dose (2 mg) has been associated with a non-significant reduction in any DVT, proximal and clinically detected DVT, but not with any bleeding complications.24 Stroke patients without reduced
mobility, usually related to lower limb paresis, should
not be routinely given low-dose anticoagulants, as the
DVT or PE risk is probably very low and bleeding complications may still occur.25
Virchow postulated that 3 factors would be of fundamental importance: 1) vessel wall damage; 2) blood flowchanges; and 3) alterations in the blood. However, venous stasis alone was insufficient to produce thrombus,
as thrombus would form when venous stasis was combined with either vessel wall damage or increased blood
coagulability.26 Oczkowski7 et al, reported that the incidence of DVT is greatest in bedridden or wheelchair-bound patients undergoing stroke rehabilitation. Age anddegree of weakness are significantly associated withpresence of DVT at the subacute phase. A stepwise increase in risk of DVT may be seen with more severe
neurological impairment, as with this study result. Stroke
patients have anatomical brain injuries and more medical
complications after stroke that may contribute to anacute inflammatory state and an increase in haemostatic
factors with a propensity for thrombosis.27 The reason
for a high frequency of soleal vein thrombosis is that thesoleal vein and soleal muscle are anatomically weak andsusceptible to exposure to venous stagnation caused byprolonged sitting.22 As the veins in soleal muscles anatomically run like a random mesh not along the muscle
fiber,28 the venous flow is easy to be disturbed by the excessive contraction of the soleal muscle (Fig. 7). Increased soleal muscle tone could induce blood pooling in
the intramuscular venous sinuses with the incompetentmuscle pump because of the specific venous structure insoleal veins. Additionally the calf muscle spasticity
could decrease the ankle joint range of movement which
disturbs the function of calf muscle venous pump. Thismight be the reason why spasticity (MAS) was significantly associated with presence of DVT. It is likely thatvessel wall damage might be encountered in hemiparetic
patients with external compression from an AFO on thecalf during gait and standing. In the rehabilitation phaseof stroke patients, combined effects on a calf muscle
with spasticity and AFOs compression could induce hemostasis, leading to vein wall distension with endothelial
damage, and metabolic damage to the endothelial lining.
Little information is available, however, regarding theKeio J Med 2008; 57 (4):196－204

association between DVT with orthotic devices commonly used in stroke patients. Kroll et al29 reported aunique case in which the use of bilateral plastic AFOs
(PAFOs) was associated with calf DVTs in a patient withchronic inflammatory demyelinating polyradiculoneuropathy. A lack of ankle joint movement reduces muscle
pump action and is likely to result in decreased resilienceof muscle tissue to pressure from the calf support of
AFOs. This pressure is therefore more likely to compress
the veins and impair venous return.29 Most of DVT patients with AFO complaint pain and tightness in the posterior aspect of hemiparetic calf with the dent at the upper calf muscle potion due to AFO upper edge in thisstudy. Using AFOs for extreme calf muscle spasticity
might induce endothelial injury and thrombosis in thecalf veins with hypercompression. Though the use of
AFO is generally useful rehabilitation intervention, medical stuff should check the extreme calf compression
with AFO which could contribute to distal DVT. The
main factors inducing DVT among stroke patients would
differ depending on the stroke phase, as severe paralysis
and immobility are present in the acute phase, whereas
the combination of disability and vein injuries is seen inrehabilitation and chronic phases. External compression
factors such as AFOs may compound the problems ofmuscle weakness and immobility and cause calf thrombus. Recent study also reported that minor injuries in theleg are associated with greater risk of DVT.30
Andre et al31 and Rodgers et al32 reported the possible
role of aspirin as a modest DVT preventive strategy frommeta-analysis data. The frequency of DVT in acutestroke is reduced by anticoagulants, but not by antiplatelet agents.17 Harvey et al10 also reported that aspirin
seemed ineffective in a large retrospective study of patients undergoing rehabilitation for stroke. Aspirin is themost popular drug to reduce mortality and recurrence of
cerebral infarction, but has not seemed to significantly
reduce the rates of DVT or PE.33-35 Although suppression of platelet-leukocyte aggregate formation was comparable between aspirin and cilostazol, cilostazol has theprotective effects of endothelial cells with swelling androughness of the surface from activated leukocytes rolling and adhesion.36 Such protective effects on the endothelium by cilostazol could reduce vein microinjury induced with spasticity and orthosis compression following DVT.
In conclusion, incidence of DVT in the rehabilitation
phase following stroke was not low (8.8%) and DVTs
were predominantly distal DVT on the hemiparetic side.
A significant association was seen between occurrenceof DVT and more severe lower limb paresis as gait disturbance. In particular, higher incidences of DVT wereassociated with severe calf muscle spasticity and use of
AFO. Micro-injuries in the venous endothelium due tospasticity and AFO might cause DVT. Cilostazol seems

203

effective for protecting against venous endothelial damage following DVT.
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